/*
 * davinci_nand.c - NAND Flash Driver for DaVinci family chips
 *
 * Copyright © 2006 Texas Instruments.
 *
 * Port to 2.6.23 Copyright © 2008 by:
 *   Sander Huijsen <Shuijsen@optelecom-nkf.com>
 *   Troy Kisky <troy.kisky@boundarydevices.com>
 *   Dirk Behme <Dirk.Behme@gmail.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/mtd/nand.h>
#include <linux/mtd/partitions.h>
#include <linux/slab.h>
#include <linux/of_device.h>
#include <linux/of.h>

#include <linux/platform_data/mtd-davinci.h>
#include <linux/platform_data/mtd-davinci-aemif.h>

/*
 * This is a device driver for the NAND flash controller found on the
 * various DaVinci family chips.  It handles up to four SoC chipselects,
 * and some flavors of secondary chipselect (e.g. based on A12) as used
 * with multichip packages.
 *
 * The 1-bit ECC hardware is supported, as well as the newer 4-bit ECC
 * available on chips like the DM355 and OMAP-L137 and needed with the
 * more error-prone MLC NAND chips.
 *
 * This driver assumes EM_WAIT connects all the NAND devices' RDY/nBUSY
 * outputs in a "wire-AND" configuration, with no per-chip signals.
 */
struct davinci_nand_info {
        struct mtd_info         mtd;
        struct nand_chip        chip;
        struct nand_ecclayout   ecclayout;

        struct device           *dev;
        struct clk              *clk;

        bool                    is_readmode;

        void __iomem            *base;
        void __iomem            *vaddr;

        uint32_t                ioaddr;
        uint32_t                current_cs;

        uint32_t                mask_chipsel;
        uint32_t                mask_ale;
        uint32_t                mask_cle;

        uint32_t                core_chipsel;

        struct davinci_aemif_timing     *timing;
};

static DEFINE_SPINLOCK(davinci_nand_lock);
static bool ecc4_busy;

#define to_davinci_nand(m) container_of(m, struct davinci_nand_info, mtd)


static inline unsigned int davinci_nand_readl(struct davinci_nand_info *info,
                int offset)
{
        return __raw_readl(info->base + offset);
}

static inline void davinci_nand_writel(struct davinci_nand_info *info,
                int offset, unsigned long value)
{
        __raw_writel(value, info->base + offset);
}

/*----------------------------------------------------------------------*/

/*
 * Access to hardware control lines:  ALE, CLE, secondary chipselect.
 */

static void nand_davinci_hwcontrol(struct mtd_info *mtd, int cmd,
                                   unsigned int ctrl)
{
        struct davinci_nand_info        *info = to_davinci_nand(mtd);
        uint32_t                        addr = info->current_cs;
        struct nand_chip                *nand = mtd->priv;

        /* Did the control lines change? */
        if (ctrl & NAND_CTRL_CHANGE) {
                if ((ctrl & NAND_CTRL_CLE) == NAND_CTRL_CLE)
                        addr |= info->mask_cle;
                else if ((ctrl & NAND_CTRL_ALE) == NAND_CTRL_ALE)
                        addr |= info->mask_ale;

                nand->IO_ADDR_W = (void __iomem __force *)addr;
        }

        if (cmd != NAND_CMD_NONE)
                iowrite8(cmd, nand->IO_ADDR_W);
}

static void nand_davinci_select_chip(struct mtd_info *mtd, int chip)
{
        struct davinci_nand_info        *info = to_davinci_nand(mtd);
        uint32_t                        addr = info->ioaddr;

        /* maybe kick in a second chipselect */
        if (chip > 0)
                addr |= info->mask_chipsel;
        info->current_cs = addr;

        info->chip.IO_ADDR_W = (void __iomem __force *)addr;
        info->chip.IO_ADDR_R = info->chip.IO_ADDR_W;
}

/*----------------------------------------------------------------------*/

/*
 * 1-bit hardware ECC ... context maintained for each core chipselect
 */

static inline uint32_t nand_davinci_readecc_1bit(struct mtd_info *mtd)
{
        struct davinci_nand_info *info = to_davinci_nand(mtd);

        return davinci_nand_readl(info, NANDF1ECC_OFFSET
                        + 4 * info->core_chipsel);
}

static void nand_davinci_hwctl_1bit(struct mtd_info *mtd, int mode)
{
        struct davinci_nand_info *info;
        uint32_t nandcfr;
        unsigned long flags;

        info = to_davinci_nand(mtd);

        /* Reset ECC hardware */
        nand_davinci_readecc_1bit(mtd);

        spin_lock_irqsave(&davinci_nand_lock, flags);

        /* Restart ECC hardware */
        nandcfr = davinci_nand_readl(info, NANDFCR_OFFSET);
        nandcfr |= BIT(8 + info->core_chipsel);
        davinci_nand_writel(info, NANDFCR_OFFSET, nandcfr);

        spin_unlock_irqrestore(&davinci_nand_lock, flags);
}

/*
 * Read hardware ECC value and pack into three bytes
 */
static int nand_davinci_calculate_1bit(struct mtd_info *mtd,
                                      const u_char *dat, u_char *ecc_code)
{
        unsigned int ecc_val = nand_davinci_readecc_1bit(mtd);
        unsigned int ecc24 = (ecc_val & 0x0fff) | ((ecc_val & 0x0fff0000) >> 4);

        /* invert so that erased block ecc is correct */
        ecc24 = ~ecc24;
        ecc_code[0] = (u_char)(ecc24);
        ecc_code[1] = (u_char)(ecc24 >> 8);
        ecc_code[2] = (u_char)(ecc24 >> 16);

        return 0;
}

static int nand_davinci_correct_1bit(struct mtd_info *mtd, u_char *dat,
                                     u_char *read_ecc, u_char *calc_ecc)
{
        struct nand_chip *chip = mtd->priv;
        uint32_t eccNand = read_ecc[0] | (read_ecc[1] << 8) |
                                          (read_ecc[2] << 16);
        uint32_t eccCalc = calc_ecc[0] | (calc_ecc[1] << 8) |
                                          (calc_ecc[2] << 16);
        uint32_t diff = eccCalc ^ eccNand;

        if (diff) {
                if ((((diff >> 12) ^ diff) & 0xfff) == 0xfff) {
                        /* Correctable error */
                        if ((diff >> (12 + 3)) < chip->ecc.size) {
                                dat[diff >> (12 + 3)] ^= BIT((diff >> 12) & 7);
                                return 1;
                        } else {
                                return -1;
                        }
                } else if (!(diff & (diff - 1))) {
                        /* Single bit ECC error in the ECC itself,
                         * nothing to fix */
                        return 1;
                } else {
                        /* Uncorrectable error */
                        return -1;
                }

        }
        return 0;
}

/*----------------------------------------------------------------------*/

/*
 * 4-bit hardware ECC ... context maintained over entire AEMIF
 *
 * This is a syndrome engine, but we avoid NAND_ECC_HW_SYNDROME
 * since that forces use of a problematic "infix OOB" layout.
 * Among other things, it trashes manufacturer bad block markers.
 * Also, and specific to this hardware, it ECC-protects the "prepad"
 * in the OOB ... while having ECC protection for parts of OOB would
 * seem useful, the current MTD stack sometimes wants to update the
 * OOB without recomputing ECC.
 */

static void nand_davinci_hwctl_4bit(struct mtd_info *mtd, int mode)
{
        struct davinci_nand_info *info = to_davinci_nand(mtd);
        unsigned long flags;
        u32 val;

        spin_lock_irqsave(&davinci_nand_lock, flags);

        /* Start 4-bit ECC calculation for read/write */
        val = davinci_nand_readl(info, NANDFCR_OFFSET);
        val &= ~(0x03 << 4);
        val |= (info->core_chipsel << 4) | BIT(12);
        davinci_nand_writel(info, NANDFCR_OFFSET, val);

        info->is_readmode = (mode == NAND_ECC_READ);

        spin_unlock_irqrestore(&davinci_nand_lock, flags);
}

/* Read raw ECC code after writing to NAND. */
static void
nand_davinci_readecc_4bit(struct davinci_nand_info *info, u32 code[4])
{
        const u32 mask = 0x03ff03ff;

        code[0] = davinci_nand_readl(info, NAND_4BIT_ECC1_OFFSET) & mask;
        code[1] = davinci_nand_readl(info, NAND_4BIT_ECC2_OFFSET) & mask;
        code[2] = davinci_nand_readl(info, NAND_4BIT_ECC3_OFFSET) & mask;
        code[3] = davinci_nand_readl(info, NAND_4BIT_ECC4_OFFSET) & mask;
}

/* Terminate read ECC; or return ECC (as bytes) of data written to NAND. */
static int nand_davinci_calculate_4bit(struct mtd_info *mtd,
                const u_char *dat, u_char *ecc_code)
{
        struct davinci_nand_info *info = to_davinci_nand(mtd);
        u32 raw_ecc[4], *p;
        unsigned i;

        /* After a read, terminate ECC calculation by a dummy read
         * of some 4-bit ECC register.  ECC covers everything that
         * was read; correct() just uses the hardware state, so
         * ecc_code is not needed.
         */
        if (info->is_readmode) {
                davinci_nand_readl(info, NAND_4BIT_ECC1_OFFSET);
                return 0;
        }

        /* Pack eight raw 10-bit ecc values into ten bytes, making
         * two passes which each convert four values (in upper and
         * lower halves of two 32-bit words) into five bytes.  The
         * ROM boot loader uses this same packing scheme.
         */
        nand_davinci_readecc_4bit(info, raw_ecc);
        for (i = 0, p = raw_ecc; i < 2; i++, p += 2) {
                *ecc_code++ =   p[0]        & 0xff;
                *ecc_code++ = ((p[0] >>  8) & 0x03) | ((p[0] >> 14) & 0xfc);
                *ecc_code++ = ((p[0] >> 22) & 0x0f) | ((p[1] <<  4) & 0xf0);
                *ecc_code++ = ((p[1] >>  4) & 0x3f) | ((p[1] >> 10) & 0xc0);
                *ecc_code++ =  (p[1] >> 18) & 0xff;
        }

        return 0;
}

/* Correct up to 4 bits in data we just read, using state left in the
 * hardware plus the ecc_code computed when it was first written.
 */
static int nand_davinci_correct_4bit(struct mtd_info *mtd,
                u_char *data, u_char *ecc_code, u_char *null)
{
        int i;
        struct davinci_nand_info *info = to_davinci_nand(mtd);
        unsigned short ecc10[8];
        unsigned short *ecc16;
        u32 syndrome[4];
        u32 ecc_state;
        unsigned num_errors, corrected;
        unsigned long timeo;

        /* All bytes 0xff?  It's an erased page; ignore its ECC. */
        for (i = 0; i < 10; i++) {
                if (ecc_code[i] != 0xff)
                        goto compare;
        }
        return 0;

compare:
        /* Unpack ten bytes into eight 10 bit values.  We know we're
         * little-endian, and use type punning for less shifting/masking.
         */
        if (WARN_ON(0x01 & (unsigned) ecc_code))
                return -EINVAL;
        ecc16 = (unsigned short *)ecc_code;

        ecc10[0] =  (ecc16[0] >>  0) & 0x3ff;
        ecc10[1] = ((ecc16[0] >> 10) & 0x3f) | ((ecc16[1] << 6) & 0x3c0);
        ecc10[2] =  (ecc16[1] >>  4) & 0x3ff;
        ecc10[3] = ((ecc16[1] >> 14) & 0x3)  | ((ecc16[2] << 2) & 0x3fc);
        ecc10[4] =  (ecc16[2] >>  8)         | ((ecc16[3] << 8) & 0x300);
        ecc10[5] =  (ecc16[3] >>  2) & 0x3ff;
        ecc10[6] = ((ecc16[3] >> 12) & 0xf)  | ((ecc16[4] << 4) & 0x3f0);
        ecc10[7] =  (ecc16[4] >>  6) & 0x3ff;

        /* Tell ECC controller about the expected ECC codes. */
        for (i = 7; i >= 0; i--)
                davinci_nand_writel(info, NAND_4BIT_ECC_LOAD_OFFSET, ecc10[i]);

        /* Allow time for syndrome calculation ... then read it.
         * A syndrome of all zeroes 0 means no detected errors.
         */
        davinci_nand_readl(info, NANDFSR_OFFSET);
        nand_davinci_readecc_4bit(info, syndrome);
        if (!(syndrome[0] | syndrome[1] | syndrome[2] | syndrome[3]))
                return 0;

        /*
         * Clear any previous address calculation by doing a dummy read of an
         * error address register.
         */
        davinci_nand_readl(info, NAND_ERR_ADD1_OFFSET);

        /* Start address calculation, and wait for it to complete.
         * We _could_ start reading more data while this is working,
         * to speed up the overall page read.
         */
        davinci_nand_writel(info, NANDFCR_OFFSET,
                        davinci_nand_readl(info, NANDFCR_OFFSET) | BIT(13));

        /*
         * ECC_STATE field reads 0x3 (Error correction complete) immediately
         * after setting the 4BITECC_ADD_CALC_START bit. So if you immediately
         * begin trying to poll for the state, you may fall right out of your
         * loop without any of the correction calculations having taken place.
         * The recommendation from the hardware team is to initially delay as
         * long as ECC_STATE reads less than 4. After that, ECC HW has entered
         * correction state.
         */
        timeo = jiffies + usecs_to_jiffies(100);
        do {
                ecc_state = (davinci_nand_readl(info,
                                NANDFSR_OFFSET) >> 8) & 0x0f;
                cpu_relax();
        } while ((ecc_state < 4) && time_before(jiffies, timeo));

        for (;;) {
                u32     fsr = davinci_nand_readl(info, NANDFSR_OFFSET);

                switch ((fsr >> 8) & 0x0f) {
                case 0:         /* no error, should not happen */
                        davinci_nand_readl(info, NAND_ERR_ERRVAL1_OFFSET);
                        return 0;
                case 1:         /* five or more errors detected */
                        davinci_nand_readl(info, NAND_ERR_ERRVAL1_OFFSET);
                        return -EIO;
                case 2:         /* error addresses computed */
                case 3:
                        num_errors = 1 + ((fsr >> 16) & 0x03);
                        goto correct;
                default:        /* still working on it */
                        cpu_relax();
                        continue;
                }
        }

correct:
        /* correct each error */
        for (i = 0, corrected = 0; i < num_errors; i++) {
                int error_address, error_value;

                if (i > 1) {
                        error_address = davinci_nand_readl(info,
                                                NAND_ERR_ADD2_OFFSET);
                        error_value = davinci_nand_readl(info,
                                                NAND_ERR_ERRVAL2_OFFSET);
                } else {
                        error_address = davinci_nand_readl(info,
                                                NAND_ERR_ADD1_OFFSET);
                        error_value = davinci_nand_readl(info,
                                                NAND_ERR_ERRVAL1_OFFSET);
                }

                if (i & 1) {
                        error_address >>= 16;
                        error_value >>= 16;
                }
                error_address &= 0x3ff;
                error_address = (512 + 7) - error_address;

                if (error_address < 512) {
                        data[error_address] ^= error_value;
                        corrected++;
                }
        }

        return corrected;
}

/*----------------------------------------------------------------------*/

/*
 * NOTE:  NAND boot requires ALE == EM_A[1], CLE == EM_A[2], so that's
 * how these chips are normally wired.  This translates to both 8 and 16
 * bit busses using ALE == BIT(3) in byte addresses, and CLE == BIT(4).
 *
 * For now we assume that configuration, or any other one which ignores
 * the two LSBs for NAND access ... so we can issue 32-bit reads/writes
 * and have that transparently morphed into multiple NAND operations.
 */
static void nand_davinci_read_buf(struct mtd_info *mtd, uint8_t *buf, int len)
{
        struct nand_chip *chip = mtd->priv;

        if ((0x03 & ((unsigned)buf)) == 0 && (0x03 & len) == 0)
                ioread32_rep(chip->IO_ADDR_R, buf, len >> 2);
        else if ((0x01 & ((unsigned)buf)) == 0 && (0x01 & len) == 0)
                ioread16_rep(chip->IO_ADDR_R, buf, len >> 1);
        else
                ioread8_rep(chip->IO_ADDR_R, buf, len);
}

static void nand_davinci_write_buf(struct mtd_info *mtd,
                const uint8_t *buf, int len)
{
        struct nand_chip *chip = mtd->priv;

        if ((0x03 & ((unsigned)buf)) == 0 && (0x03 & len) == 0)
                iowrite32_rep(chip->IO_ADDR_R, buf, len >> 2);
        else if ((0x01 & ((unsigned)buf)) == 0 && (0x01 & len) == 0)
                iowrite16_rep(chip->IO_ADDR_R, buf, len >> 1);
        else
                iowrite8_rep(chip->IO_ADDR_R, buf, len);
}

/*
 * Check hardware register for wait status. Returns 1 if device is ready,
 * 0 if it is still busy.
 */
static int nand_davinci_dev_ready(struct mtd_info *mtd)
{
        struct davinci_nand_info *info = to_davinci_nand(mtd);

        return davinci_nand_readl(info, NANDFSR_OFFSET) & BIT(0);
}

/*----------------------------------------------------------------------*/

/* An ECC layout for using 4-bit ECC with small-page flash, storing
 * ten ECC bytes plus the manufacturer's bad block marker byte, and
 * and not overlapping the default BBT markers.
 */
static struct nand_ecclayout hwecc4_small __initconst = {
        .eccbytes = 10,
        .eccpos = { 0, 1, 2, 3, 4,
                /* offset 5 holds the badblock marker */
                6, 7,
                13, 14, 15, },
        .oobfree = {
                {.offset = 8, .length = 5, },
                {.offset = 16, },
        },
};

/* An ECC layout for using 4-bit ECC with large-page (2048bytes) flash,
 * storing ten ECC bytes plus the manufacturer's bad block marker byte,
 * and not overlapping the default BBT markers.
 */
static struct nand_ecclayout hwecc4_2048 __initconst = {
        .eccbytes = 40,
        .eccpos = {
                /* at the end of spare sector */
                24, 25, 26, 27, 28, 29, 30, 31, 32, 33,
                34, 35, 36, 37, 38, 39, 40, 41, 42, 43,
                44, 45, 46, 47, 48, 49, 50, 51, 52, 53,
                54, 55, 56, 57, 58, 59, 60, 61, 62, 63,
                },
        .oobfree = {
                /* 2 bytes at offset 0 hold manufacturer badblock markers */
                {.offset = 2, .length = 22, },
                /* 5 bytes at offset 8 hold BBT markers */
                /* 8 bytes at offset 16 hold JFFS2 clean markers */
        },
};

#if defined(CONFIG_OF)
static const struct of_device_id davinci_nand_of_match[] = {
        {.compatible = "ti,davinci-nand", },
        {},
};
MODULE_DEVICE_TABLE(of, davinci_nand_of_match);

static struct davinci_nand_pdata
        *nand_davinci_get_pdata(struct platform_device *pdev)
{
        if (!dev_get_platdata(&pdev->dev) && pdev->dev.of_node) {
                struct davinci_nand_pdata *pdata;
                const char *mode;
                u32 prop;
                int len;

                pdata =  devm_kzalloc(&pdev->dev,
                                sizeof(struct davinci_nand_pdata),
                                GFP_KERNEL);
                pdev->dev.platform_data = pdata;
                if (!pdata)
                        return NULL;
                if (!of_property_read_u32(pdev->dev.of_node,
                        "ti,davinci-chipselect", &prop))
                        pdev->id = prop;
                if (!of_property_read_u32(pdev->dev.of_node,
                        "ti,davinci-mask-ale", &prop))
                        pdata->mask_ale = prop;
                if (!of_property_read_u32(pdev->dev.of_node,
                        "ti,davinci-mask-cle", &prop))
                        pdata->mask_cle = prop;
                if (!of_property_read_u32(pdev->dev.of_node,
                        "ti,davinci-mask-chipsel", &prop))
                        pdata->mask_chipsel = prop;
                if (!of_property_read_string(pdev->dev.of_node,
                        "ti,davinci-ecc-mode", &mode)) {
                        if (!strncmp("none", mode, 4))
                                pdata->ecc_mode = NAND_ECC_NONE;
                        if (!strncmp("soft", mode, 4))
                                pdata->ecc_mode = NAND_ECC_SOFT;
                        if (!strncmp("hw", mode, 2))
                                pdata->ecc_mode = NAND_ECC_HW;
                }
                if (!of_property_read_u32(pdev->dev.of_node,
                        "ti,davinci-ecc-bits", &prop))
                        pdata->ecc_bits = prop;
                if (!of_property_read_u32(pdev->dev.of_node,
                        "ti,davinci-nand-buswidth", &prop))
                        if (prop == 16)
                                pdata->options |= NAND_BUSWIDTH_16;
                if (of_find_property(pdev->dev.of_node,
                        "ti,davinci-nand-use-bbt", &len))
                        pdata->bbt_options = NAND_BBT_USE_FLASH;
        }

        return dev_get_platdata(&pdev->dev);
}
#else
static struct davinci_nand_pdata
        *nand_davinci_get_pdata(struct platform_device *pdev)
{
        return dev_get_platdata(&pdev->dev);
}
#endif

static int __init nand_davinci_probe(struct platform_device *pdev)
{
        struct davinci_nand_pdata       *pdata;
        struct davinci_nand_info        *info;
        struct resource                 *res1;
        struct resource                 *res2;
        void __iomem                    *vaddr;
        void __iomem                    *base;
        int                             ret;
        uint32_t                        val;
        nand_ecc_modes_t                ecc_mode;

        pdata = nand_davinci_get_pdata(pdev);
        /* insist on board-specific configuration */
        if (!pdata)
                return -ENODEV;

        /* which external chipselect will we be managing? */
        if (pdev->id < 0 || pdev->id > 3)
                return -ENODEV;

        info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL);
        if (!info) {
                dev_err(&pdev->dev, "unable to allocate memory\n");
                ret = -ENOMEM;
                goto err_nomem;
        }

        platform_set_drvdata(pdev, info);

        res1 = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        res2 = platform_get_resource(pdev, IORESOURCE_MEM, 1);
        if (!res1 || !res2) {
                dev_err(&pdev->dev, "resource missing\n");
                ret = -EINVAL;
                goto err_nomem;
        }

        vaddr = devm_ioremap_resource(&pdev->dev, res1);
        if (IS_ERR(vaddr)) {
                ret = PTR_ERR(vaddr);
                goto err_ioremap;
        }
        base = devm_ioremap_resource(&pdev->dev, res2);
        if (IS_ERR(base)) {
                ret = PTR_ERR(base);
                goto err_ioremap;
        }

        info->dev               = &pdev->dev;
        info->base              = base;
        info->vaddr             = vaddr;

        info->mtd.priv          = &info->chip;
        info->mtd.name          = dev_name(&pdev->dev);
        info->mtd.owner         = THIS_MODULE;

        info->mtd.dev.parent    = &pdev->dev;

        info->chip.IO_ADDR_R    = vaddr;
        info->chip.IO_ADDR_W    = vaddr;
        info->chip.chip_delay   = 0;
        info->chip.select_chip  = nand_davinci_select_chip;

        /* options such as NAND_BBT_USE_FLASH */
        info->chip.bbt_options  = pdata->bbt_options;
        /* options such as 16-bit widths */
        info->chip.options      = pdata->options;
        info->chip.bbt_td       = pdata->bbt_td;
        info->chip.bbt_md       = pdata->bbt_md;
        info->timing            = pdata->timing;

        info->ioaddr            = (uint32_t __force) vaddr;

        info->current_cs        = info->ioaddr;
        info->core_chipsel      = pdev->id;
        info->mask_chipsel      = pdata->mask_chipsel;

        /* use nandboot-capable ALE/CLE masks by default */
        info->mask_ale          = pdata->mask_ale ? : MASK_ALE;
        info->mask_cle          = pdata->mask_cle ? : MASK_CLE;

        /* Set address of hardware control function */
        info->chip.cmd_ctrl     = nand_davinci_hwcontrol;
        info->chip.dev_ready    = nand_davinci_dev_ready;

        /* Speed up buffer I/O */
        info->chip.read_buf     = nand_davinci_read_buf;
        info->chip.write_buf    = nand_davinci_write_buf;

        /* Use board-specific ECC config */
        ecc_mode                = pdata->ecc_mode;

        ret = -EINVAL;
        switch (ecc_mode) {
        case NAND_ECC_NONE:
        case NAND_ECC_SOFT:
                pdata->ecc_bits = 0;
                break;
        case NAND_ECC_HW:
                if (pdata->ecc_bits == 4) {
                        /* No sanity checks:  CPUs must support this,
                         * and the chips may not use NAND_BUSWIDTH_16.
                         */

                        /* No sharing 4-bit hardware between chipselects yet */
                        spin_lock_irq(&davinci_nand_lock);
                        if (ecc4_busy)
                                ret = -EBUSY;
                        else
                                ecc4_busy = true;
                        spin_unlock_irq(&davinci_nand_lock);

                        if (ret == -EBUSY)
                                goto err_ecc;

                        info->chip.ecc.calculate = nand_davinci_calculate_4bit;
                        info->chip.ecc.correct = nand_davinci_correct_4bit;
                        info->chip.ecc.hwctl = nand_davinci_hwctl_4bit;
                        info->chip.ecc.bytes = 10;
                } else {
                        info->chip.ecc.calculate = nand_davinci_calculate_1bit;
                        info->chip.ecc.correct = nand_davinci_correct_1bit;
                        info->chip.ecc.hwctl = nand_davinci_hwctl_1bit;
                        info->chip.ecc.bytes = 3;
                }
                info->chip.ecc.size = 512;
                info->chip.ecc.strength = pdata->ecc_bits;
                break;
        default:
                ret = -EINVAL;
                goto err_ecc;
        }
        info->chip.ecc.mode = ecc_mode;

        info->clk = devm_clk_get(&pdev->dev, "aemif");
        if (IS_ERR(info->clk)) {
                ret = PTR_ERR(info->clk);
                dev_dbg(&pdev->dev, "unable to get AEMIF clock, err %d\n", ret);
                goto err_clk;
        }

        ret = clk_prepare_enable(info->clk);
        if (ret < 0) {
                dev_dbg(&pdev->dev, "unable to enable AEMIF clock, err %d\n",
                        ret);
                goto err_clk_enable;
        }

        /*
         * Setup Async configuration register in case we did not boot from
         * NAND and so bootloader did not bother to set it up.
         */
        val = davinci_nand_readl(info, A1CR_OFFSET + info->core_chipsel * 4);

        /* Extended Wait is not valid and Select Strobe mode is not used */
        val &= ~(ACR_ASIZE_MASK | ACR_EW_MASK | ACR_SS_MASK);
        if (info->chip.options & NAND_BUSWIDTH_16)
                val |= 0x1;

        davinci_nand_writel(info, A1CR_OFFSET + info->core_chipsel * 4, val);

        ret = 0;
        if (info->timing)
                ret = davinci_aemif_setup_timing(info->timing, info->base,
                                                        info->core_chipsel);
        if (ret < 0) {
                dev_dbg(&pdev->dev, "NAND timing values setup fail\n");
                goto err_timing;
        }

        spin_lock_irq(&davinci_nand_lock);

        /* put CSxNAND into NAND mode */
        val = davinci_nand_readl(info, NANDFCR_OFFSET);
        val |= BIT(info->core_chipsel);
        davinci_nand_writel(info, NANDFCR_OFFSET, val);

        spin_unlock_irq(&davinci_nand_lock);

        /* Scan to find existence of the device(s) */
        ret = nand_scan_ident(&info->mtd, pdata->mask_chipsel ? 2 : 1, NULL);
        if (ret < 0) {
                dev_dbg(&pdev->dev, "no NAND chip(s) found\n");
                goto err_scan;
        }

        /* Update ECC layout if needed ... for 1-bit HW ECC, the default
         * is OK, but it allocates 6 bytes when only 3 are needed (for
         * each 512 bytes).  For the 4-bit HW ECC, that default is not
         * usable:  10 bytes are needed, not 6.
         */
        if (pdata->ecc_bits == 4) {
                int     chunks = info->mtd.writesize / 512;

                if (!chunks || info->mtd.oobsize < 16) {
                        dev_dbg(&pdev->dev, "too small\n");
                        ret = -EINVAL;
                        goto err_scan;
                }

                /* For small page chips, preserve the manufacturer's
                 * badblock marking data ... and make sure a flash BBT
                 * table marker fits in the free bytes.
                 */
                if (chunks == 1) {
                        info->ecclayout = hwecc4_small;
                        info->ecclayout.oobfree[1].length =
                                info->mtd.oobsize - 16;
                        goto syndrome_done;
                }
                if (chunks == 4) {
                        info->ecclayout = hwecc4_2048;
                        info->chip.ecc.mode = NAND_ECC_HW_OOB_FIRST;
                        goto syndrome_done;
                }

                /* 4KiB page chips are not yet supported. The eccpos from
                 * nand_ecclayout cannot hold 80 bytes and change to eccpos[]
                 * breaks userspace ioctl interface with mtd-utils. Once we
                 * resolve this issue, NAND_ECC_HW_OOB_FIRST mode can be used
                 * for the 4KiB page chips.
                 *
                 * TODO: Note that nand_ecclayout has now been expanded and can
                 *  hold plenty of OOB entries.
                 */
                dev_warn(&pdev->dev, "no 4-bit ECC support yet "
                                "for 4KiB-page NAND\n");
                ret = -EIO;
                goto err_scan;

syndrome_done:
                info->chip.ecc.layout = &info->ecclayout;
        }

        ret = nand_scan_tail(&info->mtd);
        if (ret < 0)
                goto err_scan;

        if (pdata->parts)
                ret = mtd_device_parse_register(&info->mtd, NULL, NULL,
                                        pdata->parts, pdata->nr_parts);
        else {
                struct mtd_part_parser_data     ppdata;

                ppdata.of_node = pdev->dev.of_node;
                ret = mtd_device_parse_register(&info->mtd, NULL, &ppdata,
                                                NULL, 0);
        }
        if (ret < 0)
                goto err_scan;

        val = davinci_nand_readl(info, NRCSR_OFFSET);
        dev_info(&pdev->dev, "controller rev. %d.%d\n",
               (val >> 8) & 0xff, val & 0xff);

        return 0;

err_scan:
err_timing:
        clk_disable_unprepare(info->clk);

err_clk_enable:
        spin_lock_irq(&davinci_nand_lock);
        if (ecc_mode == NAND_ECC_HW_SYNDROME)
                ecc4_busy = false;
        spin_unlock_irq(&davinci_nand_lock);

err_ecc:
err_clk:
err_ioremap:
err_nomem:
        return ret;
}

static int __exit nand_davinci_remove(struct platform_device *pdev)
{
        struct davinci_nand_info *info = platform_get_drvdata(pdev);

        spin_lock_irq(&davinci_nand_lock);
        if (info->chip.ecc.mode == NAND_ECC_HW_SYNDROME)
                ecc4_busy = false;
        spin_unlock_irq(&davinci_nand_lock);

        nand_release(&info->mtd);

        clk_disable_unprepare(info->clk);

        return 0;
}

static struct platform_driver nand_davinci_driver = {
        .remove         = __exit_p(nand_davinci_remove),
        .driver         = {
                .name   = "davinci_nand",
                .owner  = THIS_MODULE,
                .of_match_table = of_match_ptr(davinci_nand_of_match),
        },
};
MODULE_ALIAS("platform:davinci_nand");

module_platform_driver_probe(nand_davinci_driver, nand_davinci_probe);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Texas Instruments");
MODULE_DESCRIPTION("Davinci NAND flash driver");