// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright © 2004 Texas Instruments, Jian Zhang <jzhang@ti.com>
 * Copyright © 2004 Micron Technology Inc.
 * Copyright © 2004 David Brownell
 */

#include <linux/platform_device.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/delay.h>
#include <linux/gpio/consumer.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/jiffies.h>
#include <linux/sched.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/nand-ecc-sw-bch.h>
#include <linux/mtd/rawnand.h>
#include <linux/mtd/partitions.h>
#include <linux/omap-dma.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/of.h>
#include <linux/of_device.h>

#include <linux/platform_data/elm.h>

#include <linux/omap-gpmc.h>
#include <linux/platform_data/mtd-nand-omap2.h>

#define DRIVER_NAME     "omap2-nand"
#define OMAP_NAND_TIMEOUT_MS    5000

#define NAND_Ecc_P1e            (1 << 0)
#define NAND_Ecc_P2e            (1 << 1)
#define NAND_Ecc_P4e            (1 << 2)
#define NAND_Ecc_P8e            (1 << 3)
#define NAND_Ecc_P16e           (1 << 4)
#define NAND_Ecc_P32e           (1 << 5)
#define NAND_Ecc_P64e           (1 << 6)
#define NAND_Ecc_P128e          (1 << 7)
#define NAND_Ecc_P256e          (1 << 8)
#define NAND_Ecc_P512e          (1 << 9)
#define NAND_Ecc_P1024e         (1 << 10)
#define NAND_Ecc_P2048e         (1 << 11)

#define NAND_Ecc_P1o            (1 << 16)
#define NAND_Ecc_P2o            (1 << 17)
#define NAND_Ecc_P4o            (1 << 18)
#define NAND_Ecc_P8o            (1 << 19)
#define NAND_Ecc_P16o           (1 << 20)
#define NAND_Ecc_P32o           (1 << 21)
#define NAND_Ecc_P64o           (1 << 22)
#define NAND_Ecc_P128o          (1 << 23)
#define NAND_Ecc_P256o          (1 << 24)
#define NAND_Ecc_P512o          (1 << 25)
#define NAND_Ecc_P1024o         (1 << 26)
#define NAND_Ecc_P2048o         (1 << 27)

#define TF(value)       (value ? 1 : 0)

#define P2048e(a)       (TF(a & NAND_Ecc_P2048e)        << 0)
#define P2048o(a)       (TF(a & NAND_Ecc_P2048o)        << 1)
#define P1e(a)          (TF(a & NAND_Ecc_P1e)           << 2)
#define P1o(a)          (TF(a & NAND_Ecc_P1o)           << 3)
#define P2e(a)          (TF(a & NAND_Ecc_P2e)           << 4)
#define P2o(a)          (TF(a & NAND_Ecc_P2o)           << 5)
#define P4e(a)          (TF(a & NAND_Ecc_P4e)           << 6)
#define P4o(a)          (TF(a & NAND_Ecc_P4o)           << 7)

#define P8e(a)          (TF(a & NAND_Ecc_P8e)           << 0)
#define P8o(a)          (TF(a & NAND_Ecc_P8o)           << 1)
#define P16e(a)         (TF(a & NAND_Ecc_P16e)          << 2)
#define P16o(a)         (TF(a & NAND_Ecc_P16o)          << 3)
#define P32e(a)         (TF(a & NAND_Ecc_P32e)          << 4)
#define P32o(a)         (TF(a & NAND_Ecc_P32o)          << 5)
#define P64e(a)         (TF(a & NAND_Ecc_P64e)          << 6)
#define P64o(a)         (TF(a & NAND_Ecc_P64o)          << 7)

#define P128e(a)        (TF(a & NAND_Ecc_P128e)         << 0)
#define P128o(a)        (TF(a & NAND_Ecc_P128o)         << 1)
#define P256e(a)        (TF(a & NAND_Ecc_P256e)         << 2)
#define P256o(a)        (TF(a & NAND_Ecc_P256o)         << 3)
#define P512e(a)        (TF(a & NAND_Ecc_P512e)         << 4)
#define P512o(a)        (TF(a & NAND_Ecc_P512o)         << 5)
#define P1024e(a)       (TF(a & NAND_Ecc_P1024e)        << 6)
#define P1024o(a)       (TF(a & NAND_Ecc_P1024o)        << 7)

#define P8e_s(a)        (TF(a & NAND_Ecc_P8e)           << 0)
#define P8o_s(a)        (TF(a & NAND_Ecc_P8o)           << 1)
#define P16e_s(a)       (TF(a & NAND_Ecc_P16e)          << 2)
#define P16o_s(a)       (TF(a & NAND_Ecc_P16o)          << 3)
#define P1e_s(a)        (TF(a & NAND_Ecc_P1e)           << 4)
#define P1o_s(a)        (TF(a & NAND_Ecc_P1o)           << 5)
#define P2e_s(a)        (TF(a & NAND_Ecc_P2e)           << 6)
#define P2o_s(a)        (TF(a & NAND_Ecc_P2o)           << 7)

#define P4e_s(a)        (TF(a & NAND_Ecc_P4e)           << 0)
#define P4o_s(a)        (TF(a & NAND_Ecc_P4o)           << 1)

#define PREFETCH_CONFIG1_CS_SHIFT       24
#define ECC_CONFIG_CS_SHIFT             1
#define CS_MASK                         0x7
#define ENABLE_PREFETCH                 (0x1 << 7)
#define DMA_MPU_MODE_SHIFT              2
#define ECCSIZE0_SHIFT                  12
#define ECCSIZE1_SHIFT                  22
#define ECC1RESULTSIZE                  0x1
#define ECCCLEAR                        0x100
#define ECC1                            0x1
#define PREFETCH_FIFOTHRESHOLD_MAX      0x40
#define PREFETCH_FIFOTHRESHOLD(val)     ((val) << 8)
#define PREFETCH_STATUS_COUNT(val)      (val & 0x00003fff)
#define PREFETCH_STATUS_FIFO_CNT(val)   ((val >> 24) & 0x7F)
#define STATUS_BUFF_EMPTY               0x00000001

#define SECTOR_BYTES            512
/* 4 bit padding to make byte aligned, 56 = 52 + 4 */
#define BCH4_BIT_PAD            4

/* GPMC ecc engine settings for read */
#define BCH_WRAPMODE_1          1       /* BCH wrap mode 1 */
#define BCH8R_ECC_SIZE0         0x1a    /* ecc_size0 = 26 */
#define BCH8R_ECC_SIZE1         0x2     /* ecc_size1 = 2 */
#define BCH4R_ECC_SIZE0         0xd     /* ecc_size0 = 13 */
#define BCH4R_ECC_SIZE1         0x3     /* ecc_size1 = 3 */

/* GPMC ecc engine settings for write */
#define BCH_WRAPMODE_6          6       /* BCH wrap mode 6 */
#define BCH_ECC_SIZE0           0x0     /* ecc_size0 = 0, no oob protection */
#define BCH_ECC_SIZE1           0x20    /* ecc_size1 = 32 */

#define BBM_LEN                 2

static u_char bch16_vector[] = {0xf5, 0x24, 0x1c, 0xd0, 0x61, 0xb3, 0xf1, 0x55,
                                0x2e, 0x2c, 0x86, 0xa3, 0xed, 0x36, 0x1b, 0x78,
                                0x48, 0x76, 0xa9, 0x3b, 0x97, 0xd1, 0x7a, 0x93,
                                0x07, 0x0e};
static u_char bch8_vector[] = {0xf3, 0xdb, 0x14, 0x16, 0x8b, 0xd2, 0xbe, 0xcc,
        0xac, 0x6b, 0xff, 0x99, 0x7b};
static u_char bch4_vector[] = {0x00, 0x6b, 0x31, 0xdd, 0x41, 0xbc, 0x10};

struct omap_nand_info {
        struct nand_chip                nand;
        struct platform_device          *pdev;

        int                             gpmc_cs;
        bool                            dev_ready;
        enum nand_io                    xfer_type;
        int                             devsize;
        enum omap_ecc                   ecc_opt;
        struct device_node              *elm_of_node;

        unsigned long                   phys_base;
        struct completion               comp;
        struct dma_chan                 *dma;
        int                             gpmc_irq_fifo;
        int                             gpmc_irq_count;
        enum {
                OMAP_NAND_IO_READ = 0,  /* read */
                OMAP_NAND_IO_WRITE,     /* write */
        } iomode;
        u_char                          *buf;
        int                                     buf_len;
        /* Interface to GPMC */
        struct gpmc_nand_regs           reg;
        struct gpmc_nand_ops            *ops;
        bool                            flash_bbt;
        /* fields specific for BCHx_HW ECC scheme */
        struct device                   *elm_dev;
        /* NAND ready gpio */
        struct gpio_desc                *ready_gpiod;
        unsigned int                    neccpg;
        unsigned int                    nsteps_per_eccpg;
        unsigned int                    eccpg_size;
        unsigned int                    eccpg_bytes;
};

static inline struct omap_nand_info *mtd_to_omap(struct mtd_info *mtd)
{
        return container_of(mtd_to_nand(mtd), struct omap_nand_info, nand);
}

/**
 * omap_prefetch_enable - configures and starts prefetch transfer
 * @cs: cs (chip select) number
 * @fifo_th: fifo threshold to be used for read/ write
 * @dma_mode: dma mode enable (1) or disable (0)
 * @u32_count: number of bytes to be transferred
 * @is_write: prefetch read(0) or write post(1) mode
 * @info: NAND device structure containing platform data
 */
static int omap_prefetch_enable(int cs, int fifo_th, int dma_mode,
        unsigned int u32_count, int is_write, struct omap_nand_info *info)
{
        u32 val;

        if (fifo_th > PREFETCH_FIFOTHRESHOLD_MAX)
                return -1;

        if (readl(info->reg.gpmc_prefetch_control))
                return -EBUSY;

        /* Set the amount of bytes to be prefetched */
        writel(u32_count, info->reg.gpmc_prefetch_config2);

        /* Set dma/mpu mode, the prefetch read / post write and
         * enable the engine. Set which cs is has requested for.
         */
        val = ((cs << PREFETCH_CONFIG1_CS_SHIFT) |
                PREFETCH_FIFOTHRESHOLD(fifo_th) | ENABLE_PREFETCH |
                (dma_mode << DMA_MPU_MODE_SHIFT) | (is_write & 0x1));
        writel(val, info->reg.gpmc_prefetch_config1);

        /*  Start the prefetch engine */
        writel(0x1, info->reg.gpmc_prefetch_control);

        return 0;
}

/*
 * omap_prefetch_reset - disables and stops the prefetch engine
 */
static int omap_prefetch_reset(int cs, struct omap_nand_info *info)
{
        u32 config1;

        /* check if the same module/cs is trying to reset */
        config1 = readl(info->reg.gpmc_prefetch_config1);
        if (((config1 >> PREFETCH_CONFIG1_CS_SHIFT) & CS_MASK) != cs)
                return -EINVAL;

        /* Stop the PFPW engine */
        writel(0x0, info->reg.gpmc_prefetch_control);

        /* Reset/disable the PFPW engine */
        writel(0x0, info->reg.gpmc_prefetch_config1);

        return 0;
}

/**
 * omap_hwcontrol - hardware specific access to control-lines
 * @chip: NAND chip object
 * @cmd: command to device
 * @ctrl:
 * NAND_NCE: bit 0 -> don't care
 * NAND_CLE: bit 1 -> Command Latch
 * NAND_ALE: bit 2 -> Address Latch
 *
 * NOTE: boards may use different bits for these!!
 */
static void omap_hwcontrol(struct nand_chip *chip, int cmd, unsigned int ctrl)
{
        struct omap_nand_info *info = mtd_to_omap(nand_to_mtd(chip));

        if (cmd != NAND_CMD_NONE) {
                if (ctrl & NAND_CLE)
                        writeb(cmd, info->reg.gpmc_nand_command);

                else if (ctrl & NAND_ALE)
                        writeb(cmd, info->reg.gpmc_nand_address);

                else /* NAND_NCE */
                        writeb(cmd, info->reg.gpmc_nand_data);
        }
}

/**
 * omap_read_buf8 - read data from NAND controller into buffer
 * @mtd: MTD device structure
 * @buf: buffer to store date
 * @len: number of bytes to read
 */
static void omap_read_buf8(struct mtd_info *mtd, u_char *buf, int len)
{
        struct nand_chip *nand = mtd_to_nand(mtd);

        ioread8_rep(nand->legacy.IO_ADDR_R, buf, len);
}

/**
 * omap_write_buf8 - write buffer to NAND controller
 * @mtd: MTD device structure
 * @buf: data buffer
 * @len: number of bytes to write
 */
static void omap_write_buf8(struct mtd_info *mtd, const u_char *buf, int len)
{
        struct omap_nand_info *info = mtd_to_omap(mtd);
        u_char *p = (u_char *)buf;
        bool status;

        while (len--) {
                iowrite8(*p++, info->nand.legacy.IO_ADDR_W);
                /* wait until buffer is available for write */
                do {
                        status = info->ops->nand_writebuffer_empty();
                } while (!status);
        }
}

/**
 * omap_read_buf16 - read data from NAND controller into buffer
 * @mtd: MTD device structure
 * @buf: buffer to store date
 * @len: number of bytes to read
 */
static void omap_read_buf16(struct mtd_info *mtd, u_char *buf, int len)
{
        struct nand_chip *nand = mtd_to_nand(mtd);

        ioread16_rep(nand->legacy.IO_ADDR_R, buf, len / 2);
}

/**
 * omap_write_buf16 - write buffer to NAND controller
 * @mtd: MTD device structure
 * @buf: data buffer
 * @len: number of bytes to write
 */
static void omap_write_buf16(struct mtd_info *mtd, const u_char * buf, int len)
{
        struct omap_nand_info *info = mtd_to_omap(mtd);
        u16 *p = (u16 *) buf;
        bool status;
        /* FIXME try bursts of writesw() or DMA ... */
        len >>= 1;

        while (len--) {
                iowrite16(*p++, info->nand.legacy.IO_ADDR_W);
                /* wait until buffer is available for write */
                do {
                        status = info->ops->nand_writebuffer_empty();
                } while (!status);
        }
}

/**
 * omap_read_buf_pref - read data from NAND controller into buffer
 * @chip: NAND chip object
 * @buf: buffer to store date
 * @len: number of bytes to read
 */
static void omap_read_buf_pref(struct nand_chip *chip, u_char *buf, int len)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        struct omap_nand_info *info = mtd_to_omap(mtd);
        uint32_t r_count = 0;
        int ret = 0;
        u32 *p = (u32 *)buf;

        /* take care of subpage reads */
        if (len % 4) {
                if (info->nand.options & NAND_BUSWIDTH_16)
                        omap_read_buf16(mtd, buf, len % 4);
                else
                        omap_read_buf8(mtd, buf, len % 4);
                p = (u32 *) (buf + len % 4);
                len -= len % 4;
        }

        /* configure and start prefetch transfer */
        ret = omap_prefetch_enable(info->gpmc_cs,
                        PREFETCH_FIFOTHRESHOLD_MAX, 0x0, len, 0x0, info);
        if (ret) {
                /* PFPW engine is busy, use cpu copy method */
                if (info->nand.options & NAND_BUSWIDTH_16)
                        omap_read_buf16(mtd, (u_char *)p, len);
                else
                        omap_read_buf8(mtd, (u_char *)p, len);
        } else {
                do {
                        r_count = readl(info->reg.gpmc_prefetch_status);
                        r_count = PREFETCH_STATUS_FIFO_CNT(r_count);
                        r_count = r_count >> 2;
                        ioread32_rep(info->nand.legacy.IO_ADDR_R, p, r_count);
                        p += r_count;
                        len -= r_count << 2;
                } while (len);
                /* disable and stop the PFPW engine */
                omap_prefetch_reset(info->gpmc_cs, info);
        }
}

/**
 * omap_write_buf_pref - write buffer to NAND controller
 * @chip: NAND chip object
 * @buf: data buffer
 * @len: number of bytes to write
 */
static void omap_write_buf_pref(struct nand_chip *chip, const u_char *buf,
                                int len)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        struct omap_nand_info *info = mtd_to_omap(mtd);
        uint32_t w_count = 0;
        int i = 0, ret = 0;
        u16 *p = (u16 *)buf;
        unsigned long tim, limit;
        u32 val;

        /* take care of subpage writes */
        if (len % 2 != 0) {
                writeb(*buf, info->nand.legacy.IO_ADDR_W);
                p = (u16 *)(buf + 1);
                len--;
        }

        /*  configure and start prefetch transfer */
        ret = omap_prefetch_enable(info->gpmc_cs,
                        PREFETCH_FIFOTHRESHOLD_MAX, 0x0, len, 0x1, info);
        if (ret) {
                /* PFPW engine is busy, use cpu copy method */
                if (info->nand.options & NAND_BUSWIDTH_16)
                        omap_write_buf16(mtd, (u_char *)p, len);
                else
                        omap_write_buf8(mtd, (u_char *)p, len);
        } else {
                while (len) {
                        w_count = readl(info->reg.gpmc_prefetch_status);
                        w_count = PREFETCH_STATUS_FIFO_CNT(w_count);
                        w_count = w_count >> 1;
                        for (i = 0; (i < w_count) && len; i++, len -= 2)
                                iowrite16(*p++, info->nand.legacy.IO_ADDR_W);
                }
                /* wait for data to flushed-out before reset the prefetch */
                tim = 0;
                limit = (loops_per_jiffy *
                                        msecs_to_jiffies(OMAP_NAND_TIMEOUT_MS));
                do {
                        cpu_relax();
                        val = readl(info->reg.gpmc_prefetch_status);
                        val = PREFETCH_STATUS_COUNT(val);
                } while (val && (tim++ < limit));

                /* disable and stop the PFPW engine */
                omap_prefetch_reset(info->gpmc_cs, info);
        }
}

/*
 * omap_nand_dma_callback: callback on the completion of dma transfer
 * @data: pointer to completion data structure
 */
static void omap_nand_dma_callback(void *data)
{
        complete((struct completion *) data);
}

/*
 * omap_nand_dma_transfer: configure and start dma transfer
 * @mtd: MTD device structure
 * @addr: virtual address in RAM of source/destination
 * @len: number of data bytes to be transferred
 * @is_write: flag for read/write operation
 */
static inline int omap_nand_dma_transfer(struct mtd_info *mtd, void *addr,
                                        unsigned int len, int is_write)
{
        struct omap_nand_info *info = mtd_to_omap(mtd);
        struct dma_async_tx_descriptor *tx;
        enum dma_data_direction dir = is_write ? DMA_TO_DEVICE :
                                                        DMA_FROM_DEVICE;
        struct scatterlist sg;
        unsigned long tim, limit;
        unsigned n;
        int ret;
        u32 val;

        if (!virt_addr_valid(addr))
                goto out_copy;

        sg_init_one(&sg, addr, len);
        n = dma_map_sg(info->dma->device->dev, &sg, 1, dir);
        if (n == 0) {
                dev_err(&info->pdev->dev,
                        "Couldn't DMA map a %d byte buffer\n", len);
                goto out_copy;
        }

        tx = dmaengine_prep_slave_sg(info->dma, &sg, n,
                is_write ? DMA_MEM_TO_DEV : DMA_DEV_TO_MEM,
                DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
        if (!tx)
                goto out_copy_unmap;

        tx->callback = omap_nand_dma_callback;
        tx->callback_param = &info->comp;
        dmaengine_submit(tx);

        init_completion(&info->comp);

        /* setup and start DMA using dma_addr */
        dma_async_issue_pending(info->dma);

        /*  configure and start prefetch transfer */
        ret = omap_prefetch_enable(info->gpmc_cs,
                PREFETCH_FIFOTHRESHOLD_MAX, 0x1, len, is_write, info);
        if (ret)
                /* PFPW engine is busy, use cpu copy method */
                goto out_copy_unmap;

        wait_for_completion(&info->comp);
        tim = 0;
        limit = (loops_per_jiffy * msecs_to_jiffies(OMAP_NAND_TIMEOUT_MS));

        do {
                cpu_relax();
                val = readl(info->reg.gpmc_prefetch_status);
                val = PREFETCH_STATUS_COUNT(val);
        } while (val && (tim++ < limit));

        /* disable and stop the PFPW engine */
        omap_prefetch_reset(info->gpmc_cs, info);

        dma_unmap_sg(info->dma->device->dev, &sg, 1, dir);
        return 0;

out_copy_unmap:
        dma_unmap_sg(info->dma->device->dev, &sg, 1, dir);
out_copy:
        if (info->nand.options & NAND_BUSWIDTH_16)
                is_write == 0 ? omap_read_buf16(mtd, (u_char *) addr, len)
                        : omap_write_buf16(mtd, (u_char *) addr, len);
        else
                is_write == 0 ? omap_read_buf8(mtd, (u_char *) addr, len)
                        : omap_write_buf8(mtd, (u_char *) addr, len);
        return 0;
}

/**
 * omap_read_buf_dma_pref - read data from NAND controller into buffer
 * @chip: NAND chip object
 * @buf: buffer to store date
 * @len: number of bytes to read
 */
static void omap_read_buf_dma_pref(struct nand_chip *chip, u_char *buf,
                                   int len)
{
        struct mtd_info *mtd = nand_to_mtd(chip);

        if (len <= mtd->oobsize)
                omap_read_buf_pref(chip, buf, len);
        else
                /* start transfer in DMA mode */
                omap_nand_dma_transfer(mtd, buf, len, 0x0);
}

/**
 * omap_write_buf_dma_pref - write buffer to NAND controller
 * @chip: NAND chip object
 * @buf: data buffer
 * @len: number of bytes to write
 */
static void omap_write_buf_dma_pref(struct nand_chip *chip, const u_char *buf,
                                    int len)
{
        struct mtd_info *mtd = nand_to_mtd(chip);

        if (len <= mtd->oobsize)
                omap_write_buf_pref(chip, buf, len);
        else
                /* start transfer in DMA mode */
                omap_nand_dma_transfer(mtd, (u_char *)buf, len, 0x1);
}

/*
 * omap_nand_irq - GPMC irq handler
 * @this_irq: gpmc irq number
 * @dev: omap_nand_info structure pointer is passed here
 */
static irqreturn_t omap_nand_irq(int this_irq, void *dev)
{
        struct omap_nand_info *info = (struct omap_nand_info *) dev;
        u32 bytes;

        bytes = readl(info->reg.gpmc_prefetch_status);
        bytes = PREFETCH_STATUS_FIFO_CNT(bytes);
        bytes = bytes  & 0xFFFC; /* io in multiple of 4 bytes */
        if (info->iomode == OMAP_NAND_IO_WRITE) { /* checks for write io */
                if (this_irq == info->gpmc_irq_count)
                        goto done;

                if (info->buf_len && (info->buf_len < bytes))
                        bytes = info->buf_len;
                else if (!info->buf_len)
                        bytes = 0;
                iowrite32_rep(info->nand.legacy.IO_ADDR_W, (u32 *)info->buf,
                              bytes >> 2);
                info->buf = info->buf + bytes;
                info->buf_len -= bytes;

        } else {
                ioread32_rep(info->nand.legacy.IO_ADDR_R, (u32 *)info->buf,
                             bytes >> 2);
                info->buf = info->buf + bytes;

                if (this_irq == info->gpmc_irq_count)
                        goto done;
        }

        return IRQ_HANDLED;

done:
        complete(&info->comp);

        disable_irq_nosync(info->gpmc_irq_fifo);
        disable_irq_nosync(info->gpmc_irq_count);

        return IRQ_HANDLED;
}

/*
 * omap_read_buf_irq_pref - read data from NAND controller into buffer
 * @chip: NAND chip object
 * @buf: buffer to store date
 * @len: number of bytes to read
 */
static void omap_read_buf_irq_pref(struct nand_chip *chip, u_char *buf,
                                   int len)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        struct omap_nand_info *info = mtd_to_omap(mtd);
        int ret = 0;

        if (len <= mtd->oobsize) {
                omap_read_buf_pref(chip, buf, len);
                return;
        }

        info->iomode = OMAP_NAND_IO_READ;
        info->buf = buf;
        init_completion(&info->comp);

        /*  configure and start prefetch transfer */
        ret = omap_prefetch_enable(info->gpmc_cs,
                        PREFETCH_FIFOTHRESHOLD_MAX/2, 0x0, len, 0x0, info);
        if (ret)
                /* PFPW engine is busy, use cpu copy method */
                goto out_copy;

        info->buf_len = len;

        enable_irq(info->gpmc_irq_count);
        enable_irq(info->gpmc_irq_fifo);

        /* waiting for read to complete */
        wait_for_completion(&info->comp);

        /* disable and stop the PFPW engine */
        omap_prefetch_reset(info->gpmc_cs, info);
        return;

out_copy:
        if (info->nand.options & NAND_BUSWIDTH_16)
                omap_read_buf16(mtd, buf, len);
        else
                omap_read_buf8(mtd, buf, len);
}

/*
 * omap_write_buf_irq_pref - write buffer to NAND controller
 * @chip: NAND chip object
 * @buf: data buffer
 * @len: number of bytes to write
 */
static void omap_write_buf_irq_pref(struct nand_chip *chip, const u_char *buf,
                                    int len)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        struct omap_nand_info *info = mtd_to_omap(mtd);
        int ret = 0;
        unsigned long tim, limit;
        u32 val;

        if (len <= mtd->oobsize) {
                omap_write_buf_pref(chip, buf, len);
                return;
        }

        info->iomode = OMAP_NAND_IO_WRITE;
        info->buf = (u_char *) buf;
        init_completion(&info->comp);

        /* configure and start prefetch transfer : size=24 */
        ret = omap_prefetch_enable(info->gpmc_cs,
                (PREFETCH_FIFOTHRESHOLD_MAX * 3) / 8, 0x0, len, 0x1, info);
        if (ret)
                /* PFPW engine is busy, use cpu copy method */
                goto out_copy;

        info->buf_len = len;

        enable_irq(info->gpmc_irq_count);
        enable_irq(info->gpmc_irq_fifo);

        /* waiting for write to complete */
        wait_for_completion(&info->comp);

        /* wait for data to flushed-out before reset the prefetch */
        tim = 0;
        limit = (loops_per_jiffy *  msecs_to_jiffies(OMAP_NAND_TIMEOUT_MS));
        do {
                val = readl(info->reg.gpmc_prefetch_status);
                val = PREFETCH_STATUS_COUNT(val);
                cpu_relax();
        } while (val && (tim++ < limit));

        /* disable and stop the PFPW engine */
        omap_prefetch_reset(info->gpmc_cs, info);
        return;

out_copy:
        if (info->nand.options & NAND_BUSWIDTH_16)
                omap_write_buf16(mtd, buf, len);
        else
                omap_write_buf8(mtd, buf, len);
}

/**
 * gen_true_ecc - This function will generate true ECC value
 * @ecc_buf: buffer to store ecc code
 *
 * This generated true ECC value can be used when correcting
 * data read from NAND flash memory core
 */
static void gen_true_ecc(u8 *ecc_buf)
{
        u32 tmp = ecc_buf[0] | (ecc_buf[1] << 16) |
                ((ecc_buf[2] & 0xF0) << 20) | ((ecc_buf[2] & 0x0F) << 8);

        ecc_buf[0] = ~(P64o(tmp) | P64e(tmp) | P32o(tmp) | P32e(tmp) |
                        P16o(tmp) | P16e(tmp) | P8o(tmp) | P8e(tmp));
        ecc_buf[1] = ~(P1024o(tmp) | P1024e(tmp) | P512o(tmp) | P512e(tmp) |
                        P256o(tmp) | P256e(tmp) | P128o(tmp) | P128e(tmp));
        ecc_buf[2] = ~(P4o(tmp) | P4e(tmp) | P2o(tmp) | P2e(tmp) | P1o(tmp) |
                        P1e(tmp) | P2048o(tmp) | P2048e(tmp));
}

/**
 * omap_compare_ecc - Detect (2 bits) and correct (1 bit) error in data
 * @ecc_data1:  ecc code from nand spare area
 * @ecc_data2:  ecc code from hardware register obtained from hardware ecc
 * @page_data:  page data
 *
 * This function compares two ECC's and indicates if there is an error.
 * If the error can be corrected it will be corrected to the buffer.
 * If there is no error, %0 is returned. If there is an error but it
 * was corrected, %1 is returned. Otherwise, %-1 is returned.
 */
static int omap_compare_ecc(u8 *ecc_data1,      /* read from NAND memory */
                            u8 *ecc_data2,      /* read from register */
                            u8 *page_data)
{
        uint    i;
        u8      tmp0_bit[8], tmp1_bit[8], tmp2_bit[8];
        u8      comp0_bit[8], comp1_bit[8], comp2_bit[8];
        u8      ecc_bit[24];
        u8      ecc_sum = 0;
        u8      find_bit = 0;
        uint    find_byte = 0;
        int     isEccFF;

        isEccFF = ((*(u32 *)ecc_data1 & 0xFFFFFF) == 0xFFFFFF);

        gen_true_ecc(ecc_data1);
        gen_true_ecc(ecc_data2);

        for (i = 0; i <= 2; i++) {
                *(ecc_data1 + i) = ~(*(ecc_data1 + i));
                *(ecc_data2 + i) = ~(*(ecc_data2 + i));
        }

        for (i = 0; i < 8; i++) {
                tmp0_bit[i]     = *ecc_data1 % 2;
                *ecc_data1      = *ecc_data1 / 2;
        }

        for (i = 0; i < 8; i++) {
                tmp1_bit[i]      = *(ecc_data1 + 1) % 2;
                *(ecc_data1 + 1) = *(ecc_data1 + 1) / 2;
        }

        for (i = 0; i < 8; i++) {
                tmp2_bit[i]      = *(ecc_data1 + 2) % 2;
                *(ecc_data1 + 2) = *(ecc_data1 + 2) / 2;
        }

        for (i = 0; i < 8; i++) {
                comp0_bit[i]     = *ecc_data2 % 2;
                *ecc_data2       = *ecc_data2 / 2;
        }

        for (i = 0; i < 8; i++) {
                comp1_bit[i]     = *(ecc_data2 + 1) % 2;
                *(ecc_data2 + 1) = *(ecc_data2 + 1) / 2;
        }

        for (i = 0; i < 8; i++) {
                comp2_bit[i]     = *(ecc_data2 + 2) % 2;
                *(ecc_data2 + 2) = *(ecc_data2 + 2) / 2;
        }

        for (i = 0; i < 6; i++)
                ecc_bit[i] = tmp2_bit[i + 2] ^ comp2_bit[i + 2];

        for (i = 0; i < 8; i++)
                ecc_bit[i + 6] = tmp0_bit[i] ^ comp0_bit[i];

        for (i = 0; i < 8; i++)
                ecc_bit[i + 14] = tmp1_bit[i] ^ comp1_bit[i];

        ecc_bit[22] = tmp2_bit[0] ^ comp2_bit[0];
        ecc_bit[23] = tmp2_bit[1] ^ comp2_bit[1];

        for (i = 0; i < 24; i++)
                ecc_sum += ecc_bit[i];

        switch (ecc_sum) {
        case 0:
                /* Not reached because this function is not called if
                 *  ECC values are equal
                 */
                return 0;

        case 1:
                /* Uncorrectable error */
                pr_debug("ECC UNCORRECTED_ERROR 1\n");
                return -EBADMSG;

        case 11:
                /* UN-Correctable error */
                pr_debug("ECC UNCORRECTED_ERROR B\n");
                return -EBADMSG;

        case 12:
                /* Correctable error */
                find_byte = (ecc_bit[23] << 8) +
                            (ecc_bit[21] << 7) +
                            (ecc_bit[19] << 6) +
                            (ecc_bit[17] << 5) +
                            (ecc_bit[15] << 4) +
                            (ecc_bit[13] << 3) +
                            (ecc_bit[11] << 2) +
                            (ecc_bit[9]  << 1) +
                            ecc_bit[7];

                find_bit = (ecc_bit[5] << 2) + (ecc_bit[3] << 1) + ecc_bit[1];

                pr_debug("Correcting single bit ECC error at offset: "
                                "%d, bit: %d\n", find_byte, find_bit);

                page_data[find_byte] ^= (1 << find_bit);

                return 1;
        default:
                if (isEccFF) {
                        if (ecc_data2[0] == 0 &&
                            ecc_data2[1] == 0 &&
                            ecc_data2[2] == 0)
                                return 0;
                }
                pr_debug("UNCORRECTED_ERROR default\n");
                return -EBADMSG;
        }
}

/**
 * omap_correct_data - Compares the ECC read with HW generated ECC
 * @chip: NAND chip object
 * @dat: page data
 * @read_ecc: ecc read from nand flash
 * @calc_ecc: ecc read from HW ECC registers
 *
 * Compares the ecc read from nand spare area with ECC registers values
 * and if ECC's mismatched, it will call 'omap_compare_ecc' for error
 * detection and correction. If there are no errors, %0 is returned. If
 * there were errors and all of the errors were corrected, the number of
 * corrected errors is returned. If uncorrectable errors exist, %-1 is
 * returned.
 */
static int omap_correct_data(struct nand_chip *chip, u_char *dat,
                             u_char *read_ecc, u_char *calc_ecc)
{
        struct omap_nand_info *info = mtd_to_omap(nand_to_mtd(chip));
        int blockCnt = 0, i = 0, ret = 0;
        int stat = 0;

        /* Ex NAND_ECC_HW12_2048 */
        if (info->nand.ecc.engine_type == NAND_ECC_ENGINE_TYPE_ON_HOST &&
            info->nand.ecc.size == 2048)
                blockCnt = 4;
        else
                blockCnt = 1;

        for (i = 0; i < blockCnt; i++) {
                if (memcmp(read_ecc, calc_ecc, 3) != 0) {
                        ret = omap_compare_ecc(read_ecc, calc_ecc, dat);
                        if (ret < 0)
                                return ret;
                        /* keep track of the number of corrected errors */
                        stat += ret;
                }
                read_ecc += 3;
                calc_ecc += 3;
                dat      += 512;
        }
        return stat;
}

/**
 * omap_calculate_ecc - Generate non-inverted ECC bytes.
 * @chip: NAND chip object
 * @dat: The pointer to data on which ecc is computed
 * @ecc_code: The ecc_code buffer
 *
 * Using noninverted ECC can be considered ugly since writing a blank
 * page ie. padding will clear the ECC bytes. This is no problem as long
 * nobody is trying to write data on the seemingly unused page. Reading
 * an erased page will produce an ECC mismatch between generated and read
 * ECC bytes that has to be dealt with separately.
 */
static int omap_calculate_ecc(struct nand_chip *chip, const u_char *dat,
                              u_char *ecc_code)
{
        struct omap_nand_info *info = mtd_to_omap(nand_to_mtd(chip));
        u32 val;

        val = readl(info->reg.gpmc_ecc_config);
        if (((val >> ECC_CONFIG_CS_SHIFT) & CS_MASK) != info->gpmc_cs)
                return -EINVAL;

        /* read ecc result */
        val = readl(info->reg.gpmc_ecc1_result);
        *ecc_code++ = val;          /* P128e, ..., P1e */
        *ecc_code++ = val >> 16;    /* P128o, ..., P1o */
        /* P2048o, P1024o, P512o, P256o, P2048e, P1024e, P512e, P256e */
        *ecc_code++ = ((val >> 8) & 0x0f) | ((val >> 20) & 0xf0);

        return 0;
}

/**
 * omap_enable_hwecc - This function enables the hardware ecc functionality
 * @chip: NAND chip object
 * @mode: Read/Write mode
 */
static void omap_enable_hwecc(struct nand_chip *chip, int mode)
{
        struct omap_nand_info *info = mtd_to_omap(nand_to_mtd(chip));
        unsigned int dev_width = (chip->options & NAND_BUSWIDTH_16) ? 1 : 0;
        u32 val;

        /* clear ecc and enable bits */
        val = ECCCLEAR | ECC1;
        writel(val, info->reg.gpmc_ecc_control);

        /* program ecc and result sizes */
        val = ((((info->nand.ecc.size >> 1) - 1) << ECCSIZE1_SHIFT) |
                         ECC1RESULTSIZE);
        writel(val, info->reg.gpmc_ecc_size_config);

        switch (mode) {
        case NAND_ECC_READ:
        case NAND_ECC_WRITE:
                writel(ECCCLEAR | ECC1, info->reg.gpmc_ecc_control);
                break;
        case NAND_ECC_READSYN:
                writel(ECCCLEAR, info->reg.gpmc_ecc_control);
                break;
        default:
                dev_info(&info->pdev->dev,
                        "error: unrecognized Mode[%d]!\n", mode);
                break;
        }

        /* (ECC 16 or 8 bit col) | ( CS  )  | ECC Enable */
        val = (dev_width << 7) | (info->gpmc_cs << 1) | (0x1);
        writel(val, info->reg.gpmc_ecc_config);
}

/**
 * omap_wait - wait until the command is done
 * @this: NAND Chip structure
 *
 * Wait function is called during Program and erase operations and
 * the way it is called from MTD layer, we should wait till the NAND
 * chip is ready after the programming/erase operation has completed.
 *
 * Erase can take up to 400ms and program up to 20ms according to
 * general NAND and SmartMedia specs
 */
static int omap_wait(struct nand_chip *this)
{
        struct omap_nand_info *info = mtd_to_omap(nand_to_mtd(this));
        unsigned long timeo = jiffies;
        int status;

        timeo += msecs_to_jiffies(400);

        writeb(NAND_CMD_STATUS & 0xFF, info->reg.gpmc_nand_command);
        while (time_before(jiffies, timeo)) {
                status = readb(info->reg.gpmc_nand_data);
                if (status & NAND_STATUS_READY)
                        break;
                cond_resched();
        }

        status = readb(info->reg.gpmc_nand_data);
        return status;
}

/**
 * omap_dev_ready - checks the NAND Ready GPIO line
 * @chip: NAND chip object
 *
 * Returns true if ready and false if busy.
 */
static int omap_dev_ready(struct nand_chip *chip)
{
        struct omap_nand_info *info = mtd_to_omap(nand_to_mtd(chip));

        return gpiod_get_value(info->ready_gpiod);
}

/**
 * omap_enable_hwecc_bch - Program GPMC to perform BCH ECC calculation
 * @chip: NAND chip object
 * @mode: Read/Write mode
 *
 * When using BCH with SW correction (i.e. no ELM), sector size is set
 * to 512 bytes and we use BCH_WRAPMODE_6 wrapping mode
 * for both reading and writing with:
 * eccsize0 = 0  (no additional protected byte in spare area)
 * eccsize1 = 32 (skip 32 nibbles = 16 bytes per sector in spare area)
 */
static void __maybe_unused omap_enable_hwecc_bch(struct nand_chip *chip,
                                                 int mode)
{
        unsigned int bch_type;
        unsigned int dev_width, nsectors;
        struct omap_nand_info *info = mtd_to_omap(nand_to_mtd(chip));
        enum omap_ecc ecc_opt = info->ecc_opt;
        u32 val, wr_mode;
        unsigned int ecc_size1, ecc_size0;

        /* GPMC configurations for calculating ECC */
        switch (ecc_opt) {
        case OMAP_ECC_BCH4_CODE_HW_DETECTION_SW:
                bch_type = 0;
                nsectors = 1;
                wr_mode   = BCH_WRAPMODE_6;
                ecc_size0 = BCH_ECC_SIZE0;
                ecc_size1 = BCH_ECC_SIZE1;
                break;
        case OMAP_ECC_BCH4_CODE_HW:
                bch_type = 0;
                nsectors = chip->ecc.steps;
                if (mode == NAND_ECC_READ) {
                        wr_mode   = BCH_WRAPMODE_1;
                        ecc_size0 = BCH4R_ECC_SIZE0;
                        ecc_size1 = BCH4R_ECC_SIZE1;
                } else {
                        wr_mode   = BCH_WRAPMODE_6;
                        ecc_size0 = BCH_ECC_SIZE0;
                        ecc_size1 = BCH_ECC_SIZE1;
                }
                break;
        case OMAP_ECC_BCH8_CODE_HW_DETECTION_SW:
                bch_type = 1;
                nsectors = 1;
                wr_mode   = BCH_WRAPMODE_6;
                ecc_size0 = BCH_ECC_SIZE0;
                ecc_size1 = BCH_ECC_SIZE1;
                break;
        case OMAP_ECC_BCH8_CODE_HW:
                bch_type = 1;
                nsectors = chip->ecc.steps;
                if (mode == NAND_ECC_READ) {
                        wr_mode   = BCH_WRAPMODE_1;
                        ecc_size0 = BCH8R_ECC_SIZE0;
                        ecc_size1 = BCH8R_ECC_SIZE1;
                } else {
                        wr_mode   = BCH_WRAPMODE_6;
                        ecc_size0 = BCH_ECC_SIZE0;
                        ecc_size1 = BCH_ECC_SIZE1;
                }
                break;
        case OMAP_ECC_BCH16_CODE_HW:
                bch_type = 0x2;
                nsectors = chip->ecc.steps;
                if (mode == NAND_ECC_READ) {
                        wr_mode   = 0x01;
                        ecc_size0 = 52; /* ECC bits in nibbles per sector */
                        ecc_size1 = 0;  /* non-ECC bits in nibbles per sector */
                } else {
                        wr_mode   = 0x01;
                        ecc_size0 = 0;  /* extra bits in nibbles per sector */
                        ecc_size1 = 52; /* OOB bits in nibbles per sector */
                }
                break;
        default:
                return;
        }

        writel(ECC1, info->reg.gpmc_ecc_control);

        /* Configure ecc size for BCH */
        val = (ecc_size1 << ECCSIZE1_SHIFT) | (ecc_size0 << ECCSIZE0_SHIFT);
        writel(val, info->reg.gpmc_ecc_size_config);

        dev_width = (chip->options & NAND_BUSWIDTH_16) ? 1 : 0;

        /* BCH configuration */
        val = ((1                        << 16) | /* enable BCH */
               (bch_type                 << 12) | /* BCH4/BCH8/BCH16 */
               (wr_mode                  <<  8) | /* wrap mode */
               (dev_width                <<  7) | /* bus width */
               (((nsectors-1) & 0x7)     <<  4) | /* number of sectors */
               (info->gpmc_cs            <<  1) | /* ECC CS */
               (0x1));                            /* enable ECC */

        writel(val, info->reg.gpmc_ecc_config);

        /* Clear ecc and enable bits */
        writel(ECCCLEAR | ECC1, info->reg.gpmc_ecc_control);
}

static u8  bch4_polynomial[] = {0x28, 0x13, 0xcc, 0x39, 0x96, 0xac, 0x7f};
static u8  bch8_polynomial[] = {0xef, 0x51, 0x2e, 0x09, 0xed, 0x93, 0x9a, 0xc2,
                                0x97, 0x79, 0xe5, 0x24, 0xb5};

/**
 * _omap_calculate_ecc_bch - Generate ECC bytes for one sector
 * @mtd:        MTD device structure
 * @dat:        The pointer to data on which ecc is computed
 * @ecc_calc:   The ecc_code buffer
 * @i:          The sector number (for a multi sector page)
 *
 * Support calculating of BCH4/8/16 ECC vectors for one sector
 * within a page. Sector number is in @i.
 */
static int _omap_calculate_ecc_bch(struct mtd_info *mtd,
                                   const u_char *dat, u_char *ecc_calc, int i)
{
        struct omap_nand_info *info = mtd_to_omap(mtd);
        int eccbytes    = info->nand.ecc.bytes;
        struct gpmc_nand_regs   *gpmc_regs = &info->reg;
        u8 *ecc_code;
        unsigned long bch_val1, bch_val2, bch_val3, bch_val4;
        u32 val;
        int j;

        ecc_code = ecc_calc;
        switch (info->ecc_opt) {
        case OMAP_ECC_BCH8_CODE_HW_DETECTION_SW:
        case OMAP_ECC_BCH8_CODE_HW:
                bch_val1 = readl(gpmc_regs->gpmc_bch_result0[i]);
                bch_val2 = readl(gpmc_regs->gpmc_bch_result1[i]);
                bch_val3 = readl(gpmc_regs->gpmc_bch_result2[i]);
                bch_val4 = readl(gpmc_regs->gpmc_bch_result3[i]);
                *ecc_code++ = (bch_val4 & 0xFF);
                *ecc_code++ = ((bch_val3 >> 24) & 0xFF);
                *ecc_code++ = ((bch_val3 >> 16) & 0xFF);
                *ecc_code++ = ((bch_val3 >> 8) & 0xFF);
                *ecc_code++ = (bch_val3 & 0xFF);
                *ecc_code++ = ((bch_val2 >> 24) & 0xFF);
                *ecc_code++ = ((bch_val2 >> 16) & 0xFF);
                *ecc_code++ = ((bch_val2 >> 8) & 0xFF);
                *ecc_code++ = (bch_val2 & 0xFF);
                *ecc_code++ = ((bch_val1 >> 24) & 0xFF);
                *ecc_code++ = ((bch_val1 >> 16) & 0xFF);
                *ecc_code++ = ((bch_val1 >> 8) & 0xFF);
                *ecc_code++ = (bch_val1 & 0xFF);
                break;
        case OMAP_ECC_BCH4_CODE_HW_DETECTION_SW:
        case OMAP_ECC_BCH4_CODE_HW:
                bch_val1 = readl(gpmc_regs->gpmc_bch_result0[i]);
                bch_val2 = readl(gpmc_regs->gpmc_bch_result1[i]);
                *ecc_code++ = ((bch_val2 >> 12) & 0xFF);
                *ecc_code++ = ((bch_val2 >> 4) & 0xFF);
                *ecc_code++ = ((bch_val2 & 0xF) << 4) |
                        ((bch_val1 >> 28) & 0xF);
                *ecc_code++ = ((bch_val1 >> 20) & 0xFF);
                *ecc_code++ = ((bch_val1 >> 12) & 0xFF);
                *ecc_code++ = ((bch_val1 >> 4) & 0xFF);
                *ecc_code++ = ((bch_val1 & 0xF) << 4);
                break;
        case OMAP_ECC_BCH16_CODE_HW:
                val = readl(gpmc_regs->gpmc_bch_result6[i]);
                ecc_code[0]  = ((val >>  8) & 0xFF);
                ecc_code[1]  = ((val >>  0) & 0xFF);
                val = readl(gpmc_regs->gpmc_bch_result5[i]);
                ecc_code[2]  = ((val >> 24) & 0xFF);
                ecc_code[3]  = ((val >> 16) & 0xFF);
                ecc_code[4]  = ((val >>  8) & 0xFF);
                ecc_code[5]  = ((val >>  0) & 0xFF);
                val = readl(gpmc_regs->gpmc_bch_result4[i]);
                ecc_code[6]  = ((val >> 24) & 0xFF);
                ecc_code[7]  = ((val >> 16) & 0xFF);
                ecc_code[8]  = ((val >>  8) & 0xFF);
                ecc_code[9]  = ((val >>  0) & 0xFF);
                val = readl(gpmc_regs->gpmc_bch_result3[i]);
                ecc_code[10] = ((val >> 24) & 0xFF);
                ecc_code[11] = ((val >> 16) & 0xFF);
                ecc_code[12] = ((val >>  8) & 0xFF);
                ecc_code[13] = ((val >>  0) & 0xFF);
                val = readl(gpmc_regs->gpmc_bch_result2[i]);
                ecc_code[14] = ((val >> 24) & 0xFF);
                ecc_code[15] = ((val >> 16) & 0xFF);
                ecc_code[16] = ((val >>  8) & 0xFF);
                ecc_code[17] = ((val >>  0) & 0xFF);
                val = readl(gpmc_regs->gpmc_bch_result1[i]);
                ecc_code[18] = ((val >> 24) & 0xFF);
                ecc_code[19] = ((val >> 16) & 0xFF);
                ecc_code[20] = ((val >>  8) & 0xFF);
                ecc_code[21] = ((val >>  0) & 0xFF);
                val = readl(gpmc_regs->gpmc_bch_result0[i]);
                ecc_code[22] = ((val >> 24) & 0xFF);
                ecc_code[23] = ((val >> 16) & 0xFF);
                ecc_code[24] = ((val >>  8) & 0xFF);
                ecc_code[25] = ((val >>  0) & 0xFF);
                break;
        default:
                return -EINVAL;
        }

        /* ECC scheme specific syndrome customizations */
        switch (info->ecc_opt) {
        case OMAP_ECC_BCH4_CODE_HW_DETECTION_SW:
                /* Add constant polynomial to remainder, so that
                 * ECC of blank pages results in 0x0 on reading back
                 */
                for (j = 0; j < eccbytes; j++)
                        ecc_calc[j] ^= bch4_polynomial[j];
                break;
        case OMAP_ECC_BCH4_CODE_HW:
                /* Set  8th ECC byte as 0x0 for ROM compatibility */
                ecc_calc[eccbytes - 1] = 0x0;
                break;
        case OMAP_ECC_BCH8_CODE_HW_DETECTION_SW:
                /* Add constant polynomial to remainder, so that
                 * ECC of blank pages results in 0x0 on reading back
                 */
                for (j = 0; j < eccbytes; j++)
                        ecc_calc[j] ^= bch8_polynomial[j];
                break;
        case OMAP_ECC_BCH8_CODE_HW:
                /* Set 14th ECC byte as 0x0 for ROM compatibility */
                ecc_calc[eccbytes - 1] = 0x0;
                break;
        case OMAP_ECC_BCH16_CODE_HW:
                break;
        default:
                return -EINVAL;
        }

        return 0;
}

/**
 * omap_calculate_ecc_bch_sw - ECC generator for sector for SW based correction
 * @chip:       NAND chip object
 * @dat:        The pointer to data on which ecc is computed
 * @ecc_calc:   Buffer storing the calculated ECC bytes
 *
 * Support calculating of BCH4/8/16 ECC vectors for one sector. This is used
 * when SW based correction is required as ECC is required for one sector
 * at a time.
 */
static int omap_calculate_ecc_bch_sw(struct nand_chip *chip,
                                     const u_char *dat, u_char *ecc_calc)
{
        return _omap_calculate_ecc_bch(nand_to_mtd(chip), dat, ecc_calc, 0);
}

/**
 * omap_calculate_ecc_bch_multi - Generate ECC for multiple sectors
 * @mtd:        MTD device structure
 * @dat:        The pointer to data on which ecc is computed
 * @ecc_calc:   Buffer storing the calculated ECC bytes
 *
 * Support calculating of BCH4/8/16 ecc vectors for the entire page in one go.
 */
static int omap_calculate_ecc_bch_multi(struct mtd_info *mtd,
                                        const u_char *dat, u_char *ecc_calc)
{
        struct omap_nand_info *info = mtd_to_omap(mtd);
        int eccbytes = info->nand.ecc.bytes;
        unsigned long nsectors;
        int i, ret;

        nsectors = ((readl(info->reg.gpmc_ecc_config) >> 4) & 0x7) + 1;
        for (i = 0; i < nsectors; i++) {
                ret = _omap_calculate_ecc_bch(mtd, dat, ecc_calc, i);
                if (ret)
                        return ret;

                ecc_calc += eccbytes;
        }

        return 0;
}

/**
 * erased_sector_bitflips - count bit flips
 * @data:       data sector buffer
 * @oob:        oob buffer
 * @info:       omap_nand_info
 *
 * Check the bit flips in erased page falls below correctable level.
 * If falls below, report the page as erased with correctable bit
 * flip, else report as uncorrectable page.
 */
static int erased_sector_bitflips(u_char *data, u_char *oob,
                struct omap_nand_info *info)
{
        int flip_bits = 0, i;

        for (i = 0; i < info->nand.ecc.size; i++) {
                flip_bits += hweight8(~data[i]);
                if (flip_bits > info->nand.ecc.strength)
                        return 0;
        }

        for (i = 0; i < info->nand.ecc.bytes - 1; i++) {
                flip_bits += hweight8(~oob[i]);
                if (flip_bits > info->nand.ecc.strength)
                        return 0;
        }

        /*
         * Bit flips falls in correctable level.
         * Fill data area with 0xFF
         */
        if (flip_bits) {
                memset(data, 0xFF, info->nand.ecc.size);
                memset(oob, 0xFF, info->nand.ecc.bytes);
        }

        return flip_bits;
}

/**
 * omap_elm_correct_data - corrects page data area in case error reported
 * @chip:       NAND chip object
 * @data:       page data
 * @read_ecc:   ecc read from nand flash
 * @calc_ecc:   ecc read from HW ECC registers
 *
 * Calculated ecc vector reported as zero in case of non-error pages.
 * In case of non-zero ecc vector, first filter out erased-pages, and
 * then process data via ELM to detect bit-flips.
 */
static int omap_elm_correct_data(struct nand_chip *chip, u_char *data,
                                 u_char *read_ecc, u_char *calc_ecc)
{
        struct omap_nand_info *info = mtd_to_omap(nand_to_mtd(chip));
        struct nand_ecc_ctrl *ecc = &info->nand.ecc;
        int eccsteps = info->nsteps_per_eccpg;
        int i , j, stat = 0;
        int eccflag, actual_eccbytes;
        struct elm_errorvec err_vec[ERROR_VECTOR_MAX];
        u_char *ecc_vec = calc_ecc;
        u_char *spare_ecc = read_ecc;
        u_char *erased_ecc_vec;
        u_char *buf;
        int bitflip_count;
        bool is_error_reported = false;
        u32 bit_pos, byte_pos, error_max, pos;
        int err;

        switch (info->ecc_opt) {
        case OMAP_ECC_BCH4_CODE_HW:
                /* omit  7th ECC byte reserved for ROM code compatibility */
                actual_eccbytes = ecc->bytes - 1;
                erased_ecc_vec = bch4_vector;
                break;
        case OMAP_ECC_BCH8_CODE_HW:
                /* omit 14th ECC byte reserved for ROM code compatibility */
                actual_eccbytes = ecc->bytes - 1;
                erased_ecc_vec = bch8_vector;
                break;
        case OMAP_ECC_BCH16_CODE_HW:
                actual_eccbytes = ecc->bytes;
                erased_ecc_vec = bch16_vector;
                break;
        default:
                dev_err(&info->pdev->dev, "invalid driver configuration\n");
                return -EINVAL;
        }

        /* Initialize elm error vector to zero */
        memset(err_vec, 0, sizeof(err_vec));

        for (i = 0; i < eccsteps ; i++) {
                eccflag = 0;    /* initialize eccflag */

                /*
                 * Check any error reported,
                 * In case of error, non zero ecc reported.
                 */
                for (j = 0; j < actual_eccbytes; j++) {
                        if (calc_ecc[j] != 0) {
                                eccflag = 1; /* non zero ecc, error present */
                                break;
                        }
                }

                if (eccflag == 1) {
                        if (memcmp(calc_ecc, erased_ecc_vec,
                                                actual_eccbytes) == 0) {
                                /*
                                 * calc_ecc[] matches pattern for ECC(all 0xff)
                                 * so this is definitely an erased-page
                                 */
                        } else {
                                buf = &data[info->nand.ecc.size * i];
                                /*
                                 * count number of 0-bits in read_buf.
                                 * This check can be removed once a similar
                                 * check is introduced in generic NAND driver
                                 */
                                bitflip_count = erased_sector_bitflips(
                                                buf, read_ecc, info);
                                if (bitflip_count) {
                                        /*
                                         * number of 0-bits within ECC limits
                                         * So this may be an erased-page
                                         */
                                        stat += bitflip_count;
                                } else {
                                        /*
                                         * Too many 0-bits. It may be a
                                         * - programmed-page, OR
                                         * - erased-page with many bit-flips
                                         * So this page requires check by ELM
                                         */
                                        err_vec[i].error_reported = true;
                                        is_error_reported = true;
                                }
                        }
                }

                /* Update the ecc vector */
                calc_ecc += ecc->bytes;
                read_ecc += ecc->bytes;
        }

        /* Check if any error reported */
        if (!is_error_reported)
                return stat;

        /* Decode BCH error using ELM module */
        elm_decode_bch_error_page(info->elm_dev, ecc_vec, err_vec);

        err = 0;
        for (i = 0; i < eccsteps; i++) {
                if (err_vec[i].error_uncorrectable) {
                        dev_err(&info->pdev->dev,
                                "uncorrectable bit-flips found\n");
                        err = -EBADMSG;
                } else if (err_vec[i].error_reported) {
                        for (j = 0; j < err_vec[i].error_count; j++) {
                                switch (info->ecc_opt) {
                                case OMAP_ECC_BCH4_CODE_HW:
                                        /* Add 4 bits to take care of padding */
                                        pos = err_vec[i].error_loc[j] +
                                                BCH4_BIT_PAD;
                                        break;
                                case OMAP_ECC_BCH8_CODE_HW:
                                case OMAP_ECC_BCH16_CODE_HW:
                                        pos = err_vec[i].error_loc[j];
                                        break;
                                default:
                                        return -EINVAL;
                                }
                                error_max = (ecc->size + actual_eccbytes) * 8;
                                /* Calculate bit position of error */
                                bit_pos = pos % 8;

                                /* Calculate byte position of error */
                                byte_pos = (error_max - pos - 1) / 8;

                                if (pos < error_max) {
                                        if (byte_pos < 512) {
                                                pr_debug("bitflip@dat[%d]=%x\n",
                                                     byte_pos, data[byte_pos]);
                                                data[byte_pos] ^= 1 << bit_pos;
                                        } else {
                                                pr_debug("bitflip@oob[%d]=%x\n",
                                                        (byte_pos - 512),
                                                     spare_ecc[byte_pos - 512]);
                                                spare_ecc[byte_pos - 512] ^=
                                                        1 << bit_pos;
                                        }
                                } else {
                                        dev_err(&info->pdev->dev,
                                                "invalid bit-flip @ %d:%d\n",
                                                byte_pos, bit_pos);
                                        err = -EBADMSG;
                                }
                        }
                }

                /* Update number of correctable errors */
                stat = max_t(unsigned int, stat, err_vec[i].error_count);

                /* Update page data with sector size */
                data += ecc->size;
                spare_ecc += ecc->bytes;
        }

        return (err) ? err : stat;
}

/**
 * omap_write_page_bch - BCH ecc based write page function for entire page
 * @chip:               nand chip info structure
 * @buf:                data buffer
 * @oob_required:       must write chip->oob_poi to OOB
 * @page:               page
 *
 * Custom write page method evolved to support multi sector writing in one shot
 */
static int omap_write_page_bch(struct nand_chip *chip, const uint8_t *buf,
                               int oob_required, int page)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        struct omap_nand_info *info = mtd_to_omap(mtd);
        uint8_t *ecc_calc = chip->ecc.calc_buf;
        unsigned int eccpg;
        int ret;

        ret = nand_prog_page_begin_op(chip, page, 0, NULL, 0);
        if (ret)
                return ret;

        for (eccpg = 0; eccpg < info->neccpg; eccpg++) {
                /* Enable GPMC ecc engine */
                chip->ecc.hwctl(chip, NAND_ECC_WRITE);

                /* Write data */
                chip->legacy.write_buf(chip, buf + (eccpg * info->eccpg_size),
                                       info->eccpg_size);

                /* Update ecc vector from GPMC result registers */
                ret = omap_calculate_ecc_bch_multi(mtd,
                                                   buf + (eccpg * info->eccpg_size),
                                                   ecc_calc);
                if (ret)
                        return ret;

                ret = mtd_ooblayout_set_eccbytes(mtd, ecc_calc,
                                                 chip->oob_poi,
                                                 eccpg * info->eccpg_bytes,
                                                 info->eccpg_bytes);
                if (ret)
                        return ret;
        }

        /* Write ecc vector to OOB area */
        chip->legacy.write_buf(chip, chip->oob_poi, mtd->oobsize);

        return nand_prog_page_end_op(chip);
}

/**
 * omap_write_subpage_bch - BCH hardware ECC based subpage write
 * @chip:       nand chip info structure
 * @offset:     column address of subpage within the page
 * @data_len:   data length
 * @buf:        data buffer
 * @oob_required: must write chip->oob_poi to OOB
 * @page: page number to write
 *
 * OMAP optimized subpage write method.
 */
static int omap_write_subpage_bch(struct nand_chip *chip, u32 offset,
                                  u32 data_len, const u8 *buf,
                                  int oob_required, int page)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        struct omap_nand_info *info = mtd_to_omap(mtd);
        u8 *ecc_calc = chip->ecc.calc_buf;
        int ecc_size      = chip->ecc.size;
        int ecc_bytes     = chip->ecc.bytes;
        u32 start_step = offset / ecc_size;
        u32 end_step   = (offset + data_len - 1) / ecc_size;
        unsigned int eccpg;
        int step, ret = 0;

        /*
         * Write entire page at one go as it would be optimal
         * as ECC is calculated by hardware.
         * ECC is calculated for all subpages but we choose
         * only what we want.
         */
        ret = nand_prog_page_begin_op(chip, page, 0, NULL, 0);
        if (ret)
                return ret;

        for (eccpg = 0; eccpg < info->neccpg; eccpg++) {
                /* Enable GPMC ECC engine */
                chip->ecc.hwctl(chip, NAND_ECC_WRITE);

                /* Write data */
                chip->legacy.write_buf(chip, buf + (eccpg * info->eccpg_size),
                                       info->eccpg_size);

                for (step = 0; step < info->nsteps_per_eccpg; step++) {
                        unsigned int base_step = eccpg * info->nsteps_per_eccpg;
                        const u8 *bufoffs = buf + (eccpg * info->eccpg_size);

                        /* Mask ECC of un-touched subpages with 0xFFs */
                        if ((step + base_step) < start_step ||
                            (step + base_step) > end_step)
                                memset(ecc_calc + (step * ecc_bytes), 0xff,
                                       ecc_bytes);
                        else
                                ret = _omap_calculate_ecc_bch(mtd,
                                                              bufoffs + (step * ecc_size),
                                                              ecc_calc + (step * ecc_bytes),
                                                              step);

                        if (ret)
                                return ret;
                }

                /*
                 * Copy the calculated ECC for the whole page including the
                 * masked values (0xFF) corresponding to unwritten subpages.
                 */
                ret = mtd_ooblayout_set_eccbytes(mtd, ecc_calc, chip->oob_poi,
                                                 eccpg * info->eccpg_bytes,
                                                 info->eccpg_bytes);
                if (ret)
                        return ret;
        }

        /* write OOB buffer to NAND device */
        chip->legacy.write_buf(chip, chip->oob_poi, mtd->oobsize);

        return nand_prog_page_end_op(chip);
}

/**
 * omap_read_page_bch - BCH ecc based page read function for entire page
 * @chip:               nand chip info structure
 * @buf:                buffer to store read data
 * @oob_required:       caller requires OOB data read to chip->oob_poi
 * @page:               page number to read
 *
 * For BCH ecc scheme, GPMC used for syndrome calculation and ELM module
 * used for error correction.
 * Custom method evolved to support ELM error correction & multi sector
 * reading. On reading page data area is read along with OOB data with
 * ecc engine enabled. ecc vector updated after read of OOB data.
 * For non error pages ecc vector reported as zero.
 */
static int omap_read_page_bch(struct nand_chip *chip, uint8_t *buf,
                              int oob_required, int page)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        struct omap_nand_info *info = mtd_to_omap(mtd);
        uint8_t *ecc_calc = chip->ecc.calc_buf;
        uint8_t *ecc_code = chip->ecc.code_buf;
        unsigned int max_bitflips = 0, eccpg;
        int stat, ret;

        ret = nand_read_page_op(chip, page, 0, NULL, 0);
        if (ret)
                return ret;

        for (eccpg = 0; eccpg < info->neccpg; eccpg++) {
                /* Enable GPMC ecc engine */
                chip->ecc.hwctl(chip, NAND_ECC_READ);

                /* Read data */
                ret = nand_change_read_column_op(chip, eccpg * info->eccpg_size,
                                                 buf + (eccpg * info->eccpg_size),
                                                 info->eccpg_size, false);
                if (ret)
                        return ret;

                /* Read oob bytes */
                ret = nand_change_read_column_op(chip,
                                                 mtd->writesize + BBM_LEN +
                                                 (eccpg * info->eccpg_bytes),
                                                 chip->oob_poi + BBM_LEN +
                                                 (eccpg * info->eccpg_bytes),
                                                 info->eccpg_bytes, false);
                if (ret)
                        return ret;

                /* Calculate ecc bytes */
                ret = omap_calculate_ecc_bch_multi(mtd,
                                                   buf + (eccpg * info->eccpg_size),
                                                   ecc_calc);
                if (ret)
                        return ret;

                ret = mtd_ooblayout_get_eccbytes(mtd, ecc_code,
                                                 chip->oob_poi,
                                                 eccpg * info->eccpg_bytes,
                                                 info->eccpg_bytes);
                if (ret)
                        return ret;

                stat = chip->ecc.correct(chip,
                                         buf + (eccpg * info->eccpg_size),
                                         ecc_code, ecc_calc);
                if (stat < 0) {
                        mtd->ecc_stats.failed++;
                } else {
                        mtd->ecc_stats.corrected += stat;
                        max_bitflips = max_t(unsigned int, max_bitflips, stat);
                }
        }

        return max_bitflips;
}

/**
 * is_elm_present - checks for presence of ELM module by scanning DT nodes
 * @info: NAND device structure containing platform data
 * @elm_node: ELM's DT node
 */
static bool is_elm_present(struct omap_nand_info *info,
                           struct device_node *elm_node)
{
        struct platform_device *pdev;

        /* check whether elm-id is passed via DT */
        if (!elm_node) {
                dev_err(&info->pdev->dev, "ELM devicetree node not found\n");
                return false;
        }
        pdev = of_find_device_by_node(elm_node);
        /* check whether ELM device is registered */
        if (!pdev) {
                dev_err(&info->pdev->dev, "ELM device not found\n");
                return false;
        }
        /* ELM module available, now configure it */
        info->elm_dev = &pdev->dev;
        return true;
}

static bool omap2_nand_ecc_check(struct omap_nand_info *info)
{
        bool ecc_needs_bch, ecc_needs_omap_bch, ecc_needs_elm;

        switch (info->ecc_opt) {
        case OMAP_ECC_BCH4_CODE_HW_DETECTION_SW:
        case OMAP_ECC_BCH8_CODE_HW_DETECTION_SW:
                ecc_needs_omap_bch = false;
                ecc_needs_bch = true;
                ecc_needs_elm = false;
                break;
        case OMAP_ECC_BCH4_CODE_HW:
        case OMAP_ECC_BCH8_CODE_HW:
        case OMAP_ECC_BCH16_CODE_HW:
                ecc_needs_omap_bch = true;
                ecc_needs_bch = false;
                ecc_needs_elm = true;
                break;
        default:
                ecc_needs_omap_bch = false;
                ecc_needs_bch = false;
                ecc_needs_elm = false;
                break;
        }

        if (ecc_needs_bch && !IS_ENABLED(CONFIG_MTD_NAND_ECC_SW_BCH)) {
                dev_err(&info->pdev->dev,
                        "CONFIG_MTD_NAND_ECC_SW_BCH not enabled\n");
                return false;
        }
        if (ecc_needs_omap_bch && !IS_ENABLED(CONFIG_MTD_NAND_OMAP_BCH)) {
                dev_err(&info->pdev->dev,
                        "CONFIG_MTD_NAND_OMAP_BCH not enabled\n");
                return false;
        }
        if (ecc_needs_elm && !is_elm_present(info, info->elm_of_node)) {
                dev_err(&info->pdev->dev, "ELM not available\n");
                return false;
        }

        return true;
}

static const char * const nand_xfer_types[] = {
        [NAND_OMAP_PREFETCH_POLLED] = "prefetch-polled",
        [NAND_OMAP_POLLED] = "polled",
        [NAND_OMAP_PREFETCH_DMA] = "prefetch-dma",
        [NAND_OMAP_PREFETCH_IRQ] = "prefetch-irq",
};

static int omap_get_dt_info(struct device *dev, struct omap_nand_info *info)
{
        struct device_node *child = dev->of_node;
        int i;
        const char *s;
        u32 cs;

        if (of_property_read_u32(child, "reg", &cs) < 0) {
                dev_err(dev, "reg not found in DT\n");
                return -EINVAL;
        }

        info->gpmc_cs = cs;

        /* detect availability of ELM module. Won't be present pre-OMAP4 */
        info->elm_of_node = of_parse_phandle(child, "ti,elm-id", 0);
        if (!info->elm_of_node) {
                info->elm_of_node = of_parse_phandle(child, "elm_id", 0);
                if (!info->elm_of_node)
                        dev_dbg(dev, "ti,elm-id not in DT\n");
        }

        /* select ecc-scheme for NAND */
        if (of_property_read_string(child, "ti,nand-ecc-opt", &s)) {
                dev_err(dev, "ti,nand-ecc-opt not found\n");
                return -EINVAL;
        }

        if (!strcmp(s, "sw")) {
                info->ecc_opt = OMAP_ECC_HAM1_CODE_SW;
        } else if (!strcmp(s, "ham1") ||
                   !strcmp(s, "hw") || !strcmp(s, "hw-romcode")) {
                info->ecc_opt = OMAP_ECC_HAM1_CODE_HW;
        } else if (!strcmp(s, "bch4")) {
                if (info->elm_of_node)
                        info->ecc_opt = OMAP_ECC_BCH4_CODE_HW;
                else
                        info->ecc_opt = OMAP_ECC_BCH4_CODE_HW_DETECTION_SW;
        } else if (!strcmp(s, "bch8")) {
                if (info->elm_of_node)
                        info->ecc_opt = OMAP_ECC_BCH8_CODE_HW;
                else
                        info->ecc_opt = OMAP_ECC_BCH8_CODE_HW_DETECTION_SW;
        } else if (!strcmp(s, "bch16")) {
                info->ecc_opt = OMAP_ECC_BCH16_CODE_HW;
        } else {
                dev_err(dev, "unrecognized value for ti,nand-ecc-opt\n");
                return -EINVAL;
        }

        /* select data transfer mode */
        if (!of_property_read_string(child, "ti,nand-xfer-type", &s)) {
                for (i = 0; i < ARRAY_SIZE(nand_xfer_types); i++) {
                        if (!strcasecmp(s, nand_xfer_types[i])) {
                                info->xfer_type = i;
                                return 0;
                        }
                }

                dev_err(dev, "unrecognized value for ti,nand-xfer-type\n");
                return -EINVAL;
        }

        return 0;
}

static int omap_ooblayout_ecc(struct mtd_info *mtd, int section,
                              struct mtd_oob_region *oobregion)
{
        struct omap_nand_info *info = mtd_to_omap(mtd);
        struct nand_chip *chip = &info->nand;
        int off = BBM_LEN;

        if (info->ecc_opt == OMAP_ECC_HAM1_CODE_HW &&
            !(chip->options & NAND_BUSWIDTH_16))
                off = 1;

        if (section)
                return -ERANGE;

        oobregion->offset = off;
        oobregion->length = chip->ecc.total;

        return 0;
}

static int omap_ooblayout_free(struct mtd_info *mtd, int section,
                               struct mtd_oob_region *oobregion)
{
        struct omap_nand_info *info = mtd_to_omap(mtd);
        struct nand_chip *chip = &info->nand;
        int off = BBM_LEN;

        if (info->ecc_opt == OMAP_ECC_HAM1_CODE_HW &&
            !(chip->options & NAND_BUSWIDTH_16))
                off = 1;

        if (section)
                return -ERANGE;

        off += chip->ecc.total;
        if (off >= mtd->oobsize)
                return -ERANGE;

        oobregion->offset = off;
        oobregion->length = mtd->oobsize - off;

        return 0;
}

static const struct mtd_ooblayout_ops omap_ooblayout_ops = {
        .ecc = omap_ooblayout_ecc,
        .free = omap_ooblayout_free,
};

static int omap_sw_ooblayout_ecc(struct mtd_info *mtd, int section,
                                 struct mtd_oob_region *oobregion)
{
        struct nand_device *nand = mtd_to_nanddev(mtd);
        unsigned int nsteps = nanddev_get_ecc_nsteps(nand);
        unsigned int ecc_bytes = nanddev_get_ecc_bytes_per_step(nand);
        int off = BBM_LEN;

        if (section >= nsteps)
                return -ERANGE;

        /*
         * When SW correction is employed, one OMAP specific marker byte is
         * reserved after each ECC step.
         */
        oobregion->offset = off + (section * (ecc_bytes + 1));
        oobregion->length = ecc_bytes;

        return 0;
}

static int omap_sw_ooblayout_free(struct mtd_info *mtd, int section,
                                  struct mtd_oob_region *oobregion)
{
        struct nand_device *nand = mtd_to_nanddev(mtd);
        unsigned int nsteps = nanddev_get_ecc_nsteps(nand);
        unsigned int ecc_bytes = nanddev_get_ecc_bytes_per_step(nand);
        int off = BBM_LEN;

        if (section)
                return -ERANGE;

        /*
         * When SW correction is employed, one OMAP specific marker byte is
         * reserved after each ECC step.
         */
        off += ((ecc_bytes + 1) * nsteps);
        if (off >= mtd->oobsize)
                return -ERANGE;

        oobregion->offset = off;
        oobregion->length = mtd->oobsize - off;

        return 0;
}

static const struct mtd_ooblayout_ops omap_sw_ooblayout_ops = {
        .ecc = omap_sw_ooblayout_ecc,
        .free = omap_sw_ooblayout_free,
};

static int omap_nand_attach_chip(struct nand_chip *chip)
{
        struct mtd_info *mtd = nand_to_mtd(chip);
        struct omap_nand_info *info = mtd_to_omap(mtd);
        struct device *dev = &info->pdev->dev;
        int min_oobbytes = BBM_LEN;
        int elm_bch_strength = -1;
        int oobbytes_per_step;
        dma_cap_mask_t mask;
        int err;

        if (chip->bbt_options & NAND_BBT_USE_FLASH)
                chip->bbt_options |= NAND_BBT_NO_OOB;
        else
                chip->options |= NAND_SKIP_BBTSCAN;

        /* Re-populate low-level callbacks based on xfer modes */
        switch (info->xfer_type) {
        case NAND_OMAP_PREFETCH_POLLED:
                chip->legacy.read_buf = omap_read_buf_pref;
                chip->legacy.write_buf = omap_write_buf_pref;
                break;

        case NAND_OMAP_POLLED:
                /* Use nand_base defaults for {read,write}_buf */
                break;

        case NAND_OMAP_PREFETCH_DMA:
                dma_cap_zero(mask);
                dma_cap_set(DMA_SLAVE, mask);
                info->dma = dma_request_chan(dev->parent, "rxtx");

                if (IS_ERR(info->dma)) {

                        dev_err(dev, "DMA engine request failed\n");
                        return PTR_ERR(info->dma);
                } else {
                        struct dma_slave_config cfg;

                        memset(&cfg, 0, sizeof(cfg));
                        cfg.src_addr = info->phys_base;
                        cfg.dst_addr = info->phys_base;
                        cfg.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
                        cfg.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
                        cfg.src_maxburst = 16;
                        cfg.dst_maxburst = 16;
                        err = dmaengine_slave_config(info->dma, &cfg);
                        if (err) {
                                dev_err(dev,
                                        "DMA engine slave config failed: %d\n",
                                        err);
                                return err;
                        }
                        chip->legacy.read_buf = omap_read_buf_dma_pref;
                        chip->legacy.write_buf = omap_write_buf_dma_pref;
                }
                break;

        case NAND_OMAP_PREFETCH_IRQ:
                info->gpmc_irq_fifo = platform_get_irq(info->pdev, 0);
                if (info->gpmc_irq_fifo <= 0)
                        return -ENODEV;
                err = devm_request_irq(dev, info->gpmc_irq_fifo,
                                       omap_nand_irq, IRQF_SHARED,
                                       "gpmc-nand-fifo", info);
                if (err) {
                        dev_err(dev, "Requesting IRQ %d, error %d\n",
                                info->gpmc_irq_fifo, err);
                        info->gpmc_irq_fifo = 0;
                        return err;
                }

                info->gpmc_irq_count = platform_get_irq(info->pdev, 1);
                if (info->gpmc_irq_count <= 0)
                        return -ENODEV;
                err = devm_request_irq(dev, info->gpmc_irq_count,
                                       omap_nand_irq, IRQF_SHARED,
                                       "gpmc-nand-count", info);
                if (err) {
                        dev_err(dev, "Requesting IRQ %d, error %d\n",
                                info->gpmc_irq_count, err);
                        info->gpmc_irq_count = 0;
                        return err;
                }

                chip->legacy.read_buf = omap_read_buf_irq_pref;
                chip->legacy.write_buf = omap_write_buf_irq_pref;

                break;

        default:
                dev_err(dev, "xfer_type %d not supported!\n", info->xfer_type);
                return -EINVAL;
        }

        if (!omap2_nand_ecc_check(info))
                return -EINVAL;

        /*
         * Bail out earlier to let NAND_ECC_ENGINE_TYPE_SOFT code create its own
         * ooblayout instead of using ours.
         */
        if (info->ecc_opt == OMAP_ECC_HAM1_CODE_SW) {
                chip->ecc.engine_type = NAND_ECC_ENGINE_TYPE_SOFT;
                chip->ecc.algo = NAND_ECC_ALGO_HAMMING;
                return 0;
        }

        /* Populate MTD interface based on ECC scheme */
        switch (info->ecc_opt) {
        case OMAP_ECC_HAM1_CODE_HW:
                dev_info(dev, "nand: using OMAP_ECC_HAM1_CODE_HW\n");
                chip->ecc.engine_type   = NAND_ECC_ENGINE_TYPE_ON_HOST;
                chip->ecc.bytes         = 3;
                chip->ecc.size          = 512;
                chip->ecc.strength      = 1;
                chip->ecc.calculate     = omap_calculate_ecc;
                chip->ecc.hwctl         = omap_enable_hwecc;
                chip->ecc.correct       = omap_correct_data;
                mtd_set_ooblayout(mtd, &omap_ooblayout_ops);
                oobbytes_per_step       = chip->ecc.bytes;

                if (!(chip->options & NAND_BUSWIDTH_16))
                        min_oobbytes    = 1;

                break;

        case OMAP_ECC_BCH4_CODE_HW_DETECTION_SW:
                pr_info("nand: using OMAP_ECC_BCH4_CODE_HW_DETECTION_SW\n");
                chip->ecc.engine_type   = NAND_ECC_ENGINE_TYPE_ON_HOST;
                chip->ecc.size          = 512;
                chip->ecc.bytes         = 7;
                chip->ecc.strength      = 4;
                chip->ecc.hwctl         = omap_enable_hwecc_bch;
                chip->ecc.correct       = rawnand_sw_bch_correct;
                chip->ecc.calculate     = omap_calculate_ecc_bch_sw;
                mtd_set_ooblayout(mtd, &omap_sw_ooblayout_ops);
                /* Reserve one byte for the OMAP marker */
                oobbytes_per_step       = chip->ecc.bytes + 1;
                /* Software BCH library is used for locating errors */
                err = rawnand_sw_bch_init(chip);
                if (err) {
                        dev_err(dev, "Unable to use BCH library\n");
                        return err;
                }
                break;

        case OMAP_ECC_BCH4_CODE_HW:
                pr_info("nand: using OMAP_ECC_BCH4_CODE_HW ECC scheme\n");
                chip->ecc.engine_type   = NAND_ECC_ENGINE_TYPE_ON_HOST;
                chip->ecc.size          = 512;
                /* 14th bit is kept reserved for ROM-code compatibility */
                chip->ecc.bytes         = 7 + 1;
                chip->ecc.strength      = 4;
                chip->ecc.hwctl         = omap_enable_hwecc_bch;
                chip->ecc.correct       = omap_elm_correct_data;
                chip->ecc.read_page     = omap_read_page_bch;
                chip->ecc.write_page    = omap_write_page_bch;
                chip->ecc.write_subpage = omap_write_subpage_bch;
                mtd_set_ooblayout(mtd, &omap_ooblayout_ops);
                oobbytes_per_step       = chip->ecc.bytes;
                elm_bch_strength = BCH4_ECC;
                break;

        case OMAP_ECC_BCH8_CODE_HW_DETECTION_SW:
                pr_info("nand: using OMAP_ECC_BCH8_CODE_HW_DETECTION_SW\n");
                chip->ecc.engine_type   = NAND_ECC_ENGINE_TYPE_ON_HOST;
                chip->ecc.size          = 512;
                chip->ecc.bytes         = 13;
                chip->ecc.strength      = 8;
                chip->ecc.hwctl         = omap_enable_hwecc_bch;
                chip->ecc.correct       = rawnand_sw_bch_correct;
                chip->ecc.calculate     = omap_calculate_ecc_bch_sw;
                mtd_set_ooblayout(mtd, &omap_sw_ooblayout_ops);
                /* Reserve one byte for the OMAP marker */
                oobbytes_per_step       = chip->ecc.bytes + 1;
                /* Software BCH library is used for locating errors */
                err = rawnand_sw_bch_init(chip);
                if (err) {
                        dev_err(dev, "unable to use BCH library\n");
                        return err;
                }
                break;

        case OMAP_ECC_BCH8_CODE_HW:
                pr_info("nand: using OMAP_ECC_BCH8_CODE_HW ECC scheme\n");
                chip->ecc.engine_type   = NAND_ECC_ENGINE_TYPE_ON_HOST;
                chip->ecc.size          = 512;
                /* 14th bit is kept reserved for ROM-code compatibility */
                chip->ecc.bytes         = 13 + 1;
                chip->ecc.strength      = 8;
                chip->ecc.hwctl         = omap_enable_hwecc_bch;
                chip->ecc.correct       = omap_elm_correct_data;
                chip->ecc.read_page     = omap_read_page_bch;
                chip->ecc.write_page    = omap_write_page_bch;
                chip->ecc.write_subpage = omap_write_subpage_bch;
                mtd_set_ooblayout(mtd, &omap_ooblayout_ops);
                oobbytes_per_step       = chip->ecc.bytes;
                elm_bch_strength = BCH8_ECC;
                break;

        case OMAP_ECC_BCH16_CODE_HW:
                pr_info("Using OMAP_ECC_BCH16_CODE_HW ECC scheme\n");
                chip->ecc.engine_type   = NAND_ECC_ENGINE_TYPE_ON_HOST;
                chip->ecc.size          = 512;
                chip->ecc.bytes         = 26;
                chip->ecc.strength      = 16;
                chip->ecc.hwctl         = omap_enable_hwecc_bch;
                chip->ecc.correct       = omap_elm_correct_data;
                chip->ecc.read_page     = omap_read_page_bch;
                chip->ecc.write_page    = omap_write_page_bch;
                chip->ecc.write_subpage = omap_write_subpage_bch;
                mtd_set_ooblayout(mtd, &omap_ooblayout_ops);
                oobbytes_per_step       = chip->ecc.bytes;
                elm_bch_strength = BCH16_ECC;
                break;
        default:
                dev_err(dev, "Invalid or unsupported ECC scheme\n");
                return -EINVAL;
        }

        if (elm_bch_strength >= 0) {
                chip->ecc.steps = mtd->writesize / chip->ecc.size;
                info->neccpg = chip->ecc.steps / ERROR_VECTOR_MAX;
                if (info->neccpg) {
                        info->nsteps_per_eccpg = ERROR_VECTOR_MAX;
                } else {
                        info->neccpg = 1;
                        info->nsteps_per_eccpg = chip->ecc.steps;
                }
                info->eccpg_size = info->nsteps_per_eccpg * chip->ecc.size;
                info->eccpg_bytes = info->nsteps_per_eccpg * chip->ecc.bytes;

                err = elm_config(info->elm_dev, elm_bch_strength,
                                 info->nsteps_per_eccpg, chip->ecc.size,
                                 chip->ecc.bytes);
                if (err < 0)
                        return err;
        }

        /* Check if NAND device's OOB is enough to store ECC signatures */
        min_oobbytes += (oobbytes_per_step *
                         (mtd->writesize / chip->ecc.size));
        if (mtd->oobsize < min_oobbytes) {
                dev_err(dev,
                        "Not enough OOB bytes: required = %d, available=%d\n",
                        min_oobbytes, mtd->oobsize);
                return -EINVAL;
        }

        return 0;
}

static const struct nand_controller_ops omap_nand_controller_ops = {
        .attach_chip = omap_nand_attach_chip,
};

/* Shared among all NAND instances to synchronize access to the ECC Engine */
static struct nand_controller omap_gpmc_controller;
static bool omap_gpmc_controller_initialized;

static int omap_nand_probe(struct platform_device *pdev)
{
        struct omap_nand_info           *info;
        struct mtd_info                 *mtd;
        struct nand_chip                *nand_chip;
        int                             err;
        struct resource                 *res;
        struct device                   *dev = &pdev->dev;

        info = devm_kzalloc(&pdev->dev, sizeof(struct omap_nand_info),
                                GFP_KERNEL);
        if (!info)
                return -ENOMEM;

        info->pdev = pdev;

        err = omap_get_dt_info(dev, info);
        if (err)
                return err;

        info->ops = gpmc_omap_get_nand_ops(&info->reg, info->gpmc_cs);
        if (!info->ops) {
                dev_err(&pdev->dev, "Failed to get GPMC->NAND interface\n");
                return -ENODEV;
        }

        nand_chip               = &info->nand;
        mtd                     = nand_to_mtd(nand_chip);
        mtd->dev.parent         = &pdev->dev;
        nand_set_flash_node(nand_chip, dev->of_node);

        if (!mtd->name) {
                mtd->name = devm_kasprintf(&pdev->dev, GFP_KERNEL,
                                           "omap2-nand.%d", info->gpmc_cs);
                if (!mtd->name) {
                        dev_err(&pdev->dev, "Failed to set MTD name\n");
                        return -ENOMEM;
                }
        }

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        nand_chip->legacy.IO_ADDR_R = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(nand_chip->legacy.IO_ADDR_R))
                return PTR_ERR(nand_chip->legacy.IO_ADDR_R);

        info->phys_base = res->start;

        if (!omap_gpmc_controller_initialized) {
                omap_gpmc_controller.ops = &omap_nand_controller_ops;
                nand_controller_init(&omap_gpmc_controller);
                omap_gpmc_controller_initialized = true;
        }

        nand_chip->controller = &omap_gpmc_controller;

        nand_chip->legacy.IO_ADDR_W = nand_chip->legacy.IO_ADDR_R;
        nand_chip->legacy.cmd_ctrl  = omap_hwcontrol;

        info->ready_gpiod = devm_gpiod_get_optional(&pdev->dev, "rb",
                                                    GPIOD_IN);
        if (IS_ERR(info->ready_gpiod)) {
                dev_err(dev, "failed to get ready gpio\n");
                return PTR_ERR(info->ready_gpiod);
        }

        /*
         * If RDY/BSY line is connected to OMAP then use the omap ready
         * function and the generic nand_wait function which reads the status
         * register after monitoring the RDY/BSY line. Otherwise use a standard
         * chip delay which is slightly more than tR (AC Timing) of the NAND
         * device and read status register until you get a failure or success
         */
        if (info->ready_gpiod) {
                nand_chip->legacy.dev_ready = omap_dev_ready;
                nand_chip->legacy.chip_delay = 0;
        } else {
                nand_chip->legacy.waitfunc = omap_wait;
                nand_chip->legacy.chip_delay = 50;
        }

        if (info->flash_bbt)
                nand_chip->bbt_options |= NAND_BBT_USE_FLASH;

        /* scan NAND device connected to chip controller */
        nand_chip->options |= info->devsize & NAND_BUSWIDTH_16;

        err = nand_scan(nand_chip, 1);
        if (err)
                goto return_error;

        err = mtd_device_register(mtd, NULL, 0);
        if (err)
                goto cleanup_nand;

        platform_set_drvdata(pdev, mtd);

        return 0;

cleanup_nand:
        nand_cleanup(nand_chip);

return_error:
        if (!IS_ERR_OR_NULL(info->dma))
                dma_release_channel(info->dma);

        rawnand_sw_bch_cleanup(nand_chip);

        return err;
}

static int omap_nand_remove(struct platform_device *pdev)
{
        struct mtd_info *mtd = platform_get_drvdata(pdev);
        struct nand_chip *nand_chip = mtd_to_nand(mtd);
        struct omap_nand_info *info = mtd_to_omap(mtd);
        int ret;

        rawnand_sw_bch_cleanup(nand_chip);

        if (info->dma)
                dma_release_channel(info->dma);
        ret = mtd_device_unregister(mtd);
        WARN_ON(ret);
        nand_cleanup(nand_chip);
        return ret;
}

static const struct of_device_id omap_nand_ids[] = {
        { .compatible = "ti,omap2-nand", },
        {},
};
MODULE_DEVICE_TABLE(of, omap_nand_ids);

static struct platform_driver omap_nand_driver = {
        .probe          = omap_nand_probe,
        .remove         = omap_nand_remove,
        .driver         = {
                .name   = DRIVER_NAME,
                .of_match_table = of_match_ptr(omap_nand_ids),
        },
};

module_platform_driver(omap_nand_driver);

MODULE_ALIAS("platform:" DRIVER_NAME);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("Glue layer for NAND flash on TI OMAP boards");