/*
 * Freescale GPMI NAND Flash Driver
 *
 * Copyright (C) 2010-2011 Freescale Semiconductor, Inc.
 * Copyright (C) 2008 Embedded Alley Solutions, Inc.
 *
 * 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.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
#include <linux/clk.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/mtd/partitions.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/of_mtd.h>
#include "gpmi-nand.h"
#include "bch-regs.h"

/* Resource names for the GPMI NAND driver. */
#define GPMI_NAND_GPMI_REGS_ADDR_RES_NAME  "gpmi-nand"
#define GPMI_NAND_BCH_REGS_ADDR_RES_NAME   "bch"
#define GPMI_NAND_BCH_INTERRUPT_RES_NAME   "bch"

/* add our owner bbt descriptor */
static uint8_t scan_ff_pattern[] = { 0xff };
static struct nand_bbt_descr gpmi_bbt_descr = {
        .options        = 0,
        .offs           = 0,
        .len            = 1,
        .pattern        = scan_ff_pattern
};

/*
 * We may change the layout if we can get the ECC info from the datasheet,
 * else we will use all the (page + OOB).
 */
static struct nand_ecclayout gpmi_hw_ecclayout = {
        .eccbytes = 0,
        .eccpos = { 0, },
        .oobfree = { {.offset = 0, .length = 0} }
};

static const struct gpmi_devdata gpmi_devdata_imx23 = {
        .type = IS_MX23,
        .bch_max_ecc_strength = 20,
        .max_chain_delay = 16,
};

static const struct gpmi_devdata gpmi_devdata_imx28 = {
        .type = IS_MX28,
        .bch_max_ecc_strength = 20,
        .max_chain_delay = 16,
};

static const struct gpmi_devdata gpmi_devdata_imx6q = {
        .type = IS_MX6Q,
        .bch_max_ecc_strength = 40,
        .max_chain_delay = 12,
};

static const struct gpmi_devdata gpmi_devdata_imx6sx = {
        .type = IS_MX6SX,
        .bch_max_ecc_strength = 62,
        .max_chain_delay = 12,
};

static irqreturn_t bch_irq(int irq, void *cookie)
{
        struct gpmi_nand_data *this = cookie;

        gpmi_clear_bch(this);
        complete(&this->bch_done);
        return IRQ_HANDLED;
}

/*
 *  Calculate the ECC strength by hand:
 *      E : The ECC strength.
 *      G : the length of Galois Field.
 *      N : The chunk count of per page.
 *      O : the oobsize of the NAND chip.
 *      M : the metasize of per page.
 *
 *      The formula is :
 *              E * G * N
 *            ------------ <= (O - M)
 *                  8
 *
 *      So, we get E by:
 *                    (O - M) * 8
 *              E <= -------------
 *                       G * N
 */
static inline int get_ecc_strength(struct gpmi_nand_data *this)
{
        struct bch_geometry *geo = &this->bch_geometry;
        struct mtd_info *mtd = &this->mtd;
        int ecc_strength;

        ecc_strength = ((mtd->oobsize - geo->metadata_size) * 8)
                        / (geo->gf_len * geo->ecc_chunk_count);

        /* We need the minor even number. */
        return round_down(ecc_strength, 2);
}

static inline bool gpmi_check_ecc(struct gpmi_nand_data *this)
{
        struct bch_geometry *geo = &this->bch_geometry;

        /* Do the sanity check. */
        if (GPMI_IS_MX23(this) || GPMI_IS_MX28(this)) {
                /* The mx23/mx28 only support the GF13. */
                if (geo->gf_len == 14)
                        return false;
        }
        return geo->ecc_strength <= this->devdata->bch_max_ecc_strength;
}

/*
 * If we can get the ECC information from the nand chip, we do not
 * need to calculate them ourselves.
 *
 * We may have available oob space in this case.
 */
static bool set_geometry_by_ecc_info(struct gpmi_nand_data *this)
{
        struct bch_geometry *geo = &this->bch_geometry;
        struct mtd_info *mtd = &this->mtd;
        struct nand_chip *chip = mtd->priv;
        struct nand_oobfree *of = gpmi_hw_ecclayout.oobfree;
        unsigned int block_mark_bit_offset;

        if (!(chip->ecc_strength_ds > 0 && chip->ecc_step_ds > 0))
                return false;

        switch (chip->ecc_step_ds) {
        case SZ_512:
                geo->gf_len = 13;
                break;
        case SZ_1K:
                geo->gf_len = 14;
                break;
        default:
                dev_err(this->dev,
                        "unsupported nand chip. ecc bits : %d, ecc size : %d\n",
                        chip->ecc_strength_ds, chip->ecc_step_ds);
                return false;
        }
        geo->ecc_chunk_size = chip->ecc_step_ds;
        geo->ecc_strength = round_up(chip->ecc_strength_ds, 2);
        if (!gpmi_check_ecc(this))
                return false;

        /* Keep the C >= O */
        if (geo->ecc_chunk_size < mtd->oobsize) {
                dev_err(this->dev,
                        "unsupported nand chip. ecc size: %d, oob size : %d\n",
                        chip->ecc_step_ds, mtd->oobsize);
                return false;
        }

        /* The default value, see comment in the legacy_set_geometry(). */
        geo->metadata_size = 10;

        geo->ecc_chunk_count = mtd->writesize / geo->ecc_chunk_size;

        /*
         * Now, the NAND chip with 2K page(data chunk is 512byte) shows below:
         *
         *    |                          P                            |
         *    |<----------------------------------------------------->|
         *    |                                                       |
         *    |                                        (Block Mark)   |
         *    |                      P'                      |      | |     |
         *    |<-------------------------------------------->|  D   | |  O' |
         *    |                                              |<---->| |<--->|
         *    V                                              V      V V     V
         *    +---+----------+-+----------+-+----------+-+----------+-+-----+
         *    | M |   data   |E|   data   |E|   data   |E|   data   |E|     |
         *    +---+----------+-+----------+-+----------+-+----------+-+-----+
         *                                                   ^              ^
         *                                                   |      O       |
         *                                                   |<------------>|
         *                                                   |              |
         *
         *      P : the page size for BCH module.
         *      E : The ECC strength.
         *      G : the length of Galois Field.
         *      N : The chunk count of per page.
         *      M : the metasize of per page.
         *      C : the ecc chunk size, aka the "data" above.
         *      P': the nand chip's page size.
         *      O : the nand chip's oob size.
         *      O': the free oob.
         *
         *      The formula for P is :
         *
         *                  E * G * N
         *             P = ------------ + P' + M
         *                      8
         *
         * The position of block mark moves forward in the ECC-based view
         * of page, and the delta is:
         *
         *                   E * G * (N - 1)
         *             D = (---------------- + M)
         *                          8
         *
         * Please see the comment in legacy_set_geometry().
         * With the condition C >= O , we still can get same result.
         * So the bit position of the physical block mark within the ECC-based
         * view of the page is :
         *             (P' - D) * 8
         */
        geo->page_size = mtd->writesize + geo->metadata_size +
                (geo->gf_len * geo->ecc_strength * geo->ecc_chunk_count) / 8;

        /* The available oob size we have. */
        if (geo->page_size < mtd->writesize + mtd->oobsize) {
                of->offset = geo->page_size - mtd->writesize;
                of->length = mtd->oobsize - of->offset;
        }

        geo->payload_size = mtd->writesize;

        geo->auxiliary_status_offset = ALIGN(geo->metadata_size, 4);
        geo->auxiliary_size = ALIGN(geo->metadata_size, 4)
                                + ALIGN(geo->ecc_chunk_count, 4);

        if (!this->swap_block_mark)
                return true;

        /* For bit swap. */
        block_mark_bit_offset = mtd->writesize * 8 -
                (geo->ecc_strength * geo->gf_len * (geo->ecc_chunk_count - 1)
                                + geo->metadata_size * 8);

        geo->block_mark_byte_offset = block_mark_bit_offset / 8;
        geo->block_mark_bit_offset  = block_mark_bit_offset % 8;
        return true;
}

static int legacy_set_geometry(struct gpmi_nand_data *this)
{
        struct bch_geometry *geo = &this->bch_geometry;
        struct mtd_info *mtd = &this->mtd;
        unsigned int metadata_size;
        unsigned int status_size;
        unsigned int block_mark_bit_offset;

        /*
         * The size of the metadata can be changed, though we set it to 10
         * bytes now. But it can't be too large, because we have to save
         * enough space for BCH.
         */
        geo->metadata_size = 10;

        /* The default for the length of Galois Field. */
        geo->gf_len = 13;

        /* The default for chunk size. */
        geo->ecc_chunk_size = 512;
        while (geo->ecc_chunk_size < mtd->oobsize) {
                geo->ecc_chunk_size *= 2; /* keep C >= O */
                geo->gf_len = 14;
        }

        geo->ecc_chunk_count = mtd->writesize / geo->ecc_chunk_size;

        /* We use the same ECC strength for all chunks. */
        geo->ecc_strength = get_ecc_strength(this);
        if (!gpmi_check_ecc(this)) {
                dev_err(this->dev,
                        "required ecc strength of the NAND chip: %d is not supported by the GPMI controller (%d)\n",
                        geo->ecc_strength,
                        this->devdata->bch_max_ecc_strength);
                return -EINVAL;
        }

        geo->page_size = mtd->writesize + mtd->oobsize;
        geo->payload_size = mtd->writesize;

        /*
         * The auxiliary buffer contains the metadata and the ECC status. The
         * metadata is padded to the nearest 32-bit boundary. The ECC status
         * contains one byte for every ECC chunk, and is also padded to the
         * nearest 32-bit boundary.
         */
        metadata_size = ALIGN(geo->metadata_size, 4);
        status_size   = ALIGN(geo->ecc_chunk_count, 4);

        geo->auxiliary_size = metadata_size + status_size;
        geo->auxiliary_status_offset = metadata_size;

        if (!this->swap_block_mark)
                return 0;

        /*
         * We need to compute the byte and bit offsets of
         * the physical block mark within the ECC-based view of the page.
         *
         * NAND chip with 2K page shows below:
         *                                             (Block Mark)
         *                                                   |      |
         *                                                   |  D   |
         *                                                   |<---->|
         *                                                   V      V
         *    +---+----------+-+----------+-+----------+-+----------+-+
         *    | M |   data   |E|   data   |E|   data   |E|   data   |E|
         *    +---+----------+-+----------+-+----------+-+----------+-+
         *
         * The position of block mark moves forward in the ECC-based view
         * of page, and the delta is:
         *
         *                   E * G * (N - 1)
         *             D = (---------------- + M)
         *                          8
         *
         * With the formula to compute the ECC strength, and the condition
         *       : C >= O         (C is the ecc chunk size)
         *
         * It's easy to deduce to the following result:
         *
         *         E * G       (O - M)      C - M         C - M
         *      ----------- <= ------- <=  --------  <  ---------
         *           8            N           N          (N - 1)
         *
         *  So, we get:
         *
         *                   E * G * (N - 1)
         *             D = (---------------- + M) < C
         *                          8
         *
         *  The above inequality means the position of block mark
         *  within the ECC-based view of the page is still in the data chunk,
         *  and it's NOT in the ECC bits of the chunk.
         *
         *  Use the following to compute the bit position of the
         *  physical block mark within the ECC-based view of the page:
         *          (page_size - D) * 8
         *
         *  --Huang Shijie
         */
        block_mark_bit_offset = mtd->writesize * 8 -
                (geo->ecc_strength * geo->gf_len * (geo->ecc_chunk_count - 1)
                                + geo->metadata_size * 8);

        geo->block_mark_byte_offset = block_mark_bit_offset / 8;
        geo->block_mark_bit_offset  = block_mark_bit_offset % 8;
        return 0;
}

int common_nfc_set_geometry(struct gpmi_nand_data *this)
{
        if (of_property_read_bool(this->dev->of_node, "fsl,use-minimum-ecc")
                && set_geometry_by_ecc_info(this))
                return 0;
        return legacy_set_geometry(this);
}

struct dma_chan *get_dma_chan(struct gpmi_nand_data *this)
{
        /* We use the DMA channel 0 to access all the nand chips. */
        return this->dma_chans[0];
}

/* Can we use the upper's buffer directly for DMA? */
void prepare_data_dma(struct gpmi_nand_data *this, enum dma_data_direction dr)
{
        struct scatterlist *sgl = &this->data_sgl;
        int ret;

        /* first try to map the upper buffer directly */
        if (virt_addr_valid(this->upper_buf) &&
                !object_is_on_stack(this->upper_buf)) {
                sg_init_one(sgl, this->upper_buf, this->upper_len);
                ret = dma_map_sg(this->dev, sgl, 1, dr);
                if (ret == 0)
                        goto map_fail;

                this->direct_dma_map_ok = true;
                return;
        }

map_fail:
        /* We have to use our own DMA buffer. */
        sg_init_one(sgl, this->data_buffer_dma, this->upper_len);

        if (dr == DMA_TO_DEVICE)
                memcpy(this->data_buffer_dma, this->upper_buf, this->upper_len);

        dma_map_sg(this->dev, sgl, 1, dr);

        this->direct_dma_map_ok = false;
}

/* This will be called after the DMA operation is finished. */
static void dma_irq_callback(void *param)
{
        struct gpmi_nand_data *this = param;
        struct completion *dma_c = &this->dma_done;

        switch (this->dma_type) {
        case DMA_FOR_COMMAND:
                dma_unmap_sg(this->dev, &this->cmd_sgl, 1, DMA_TO_DEVICE);
                break;

        case DMA_FOR_READ_DATA:
                dma_unmap_sg(this->dev, &this->data_sgl, 1, DMA_FROM_DEVICE);
                if (this->direct_dma_map_ok == false)
                        memcpy(this->upper_buf, this->data_buffer_dma,
                                this->upper_len);
                break;

        case DMA_FOR_WRITE_DATA:
                dma_unmap_sg(this->dev, &this->data_sgl, 1, DMA_TO_DEVICE);
                break;

        case DMA_FOR_READ_ECC_PAGE:
        case DMA_FOR_WRITE_ECC_PAGE:
                /* We have to wait the BCH interrupt to finish. */
                break;

        default:
                dev_err(this->dev, "in wrong DMA operation.\n");
        }

        complete(dma_c);
}

int start_dma_without_bch_irq(struct gpmi_nand_data *this,
                                struct dma_async_tx_descriptor *desc)
{
        struct completion *dma_c = &this->dma_done;
        int err;

        init_completion(dma_c);

        desc->callback          = dma_irq_callback;
        desc->callback_param    = this;
        dmaengine_submit(desc);
        dma_async_issue_pending(get_dma_chan(this));

        /* Wait for the interrupt from the DMA block. */
        err = wait_for_completion_timeout(dma_c, msecs_to_jiffies(1000));
        if (!err) {
                dev_err(this->dev, "DMA timeout, last DMA :%d\n",
                        this->last_dma_type);
                gpmi_dump_info(this);
                return -ETIMEDOUT;
        }
        return 0;
}

/*
 * This function is used in BCH reading or BCH writing pages.
 * It will wait for the BCH interrupt as long as ONE second.
 * Actually, we must wait for two interrupts :
 *      [1] firstly the DMA interrupt and
 *      [2] secondly the BCH interrupt.
 */
int start_dma_with_bch_irq(struct gpmi_nand_data *this,
                        struct dma_async_tx_descriptor *desc)
{
        struct completion *bch_c = &this->bch_done;
        int err;

        /* Prepare to receive an interrupt from the BCH block. */
        init_completion(bch_c);

        /* start the DMA */
        start_dma_without_bch_irq(this, desc);

        /* Wait for the interrupt from the BCH block. */
        err = wait_for_completion_timeout(bch_c, msecs_to_jiffies(1000));
        if (!err) {
                dev_err(this->dev, "BCH timeout, last DMA :%d\n",
                        this->last_dma_type);
                gpmi_dump_info(this);
                return -ETIMEDOUT;
        }
        return 0;
}

static int acquire_register_block(struct gpmi_nand_data *this,
                                  const char *res_name)
{
        struct platform_device *pdev = this->pdev;
        struct resources *res = &this->resources;
        struct resource *r;
        void __iomem *p;

        r = platform_get_resource_byname(pdev, IORESOURCE_MEM, res_name);
        p = devm_ioremap_resource(&pdev->dev, r);
        if (IS_ERR(p))
                return PTR_ERR(p);

        if (!strcmp(res_name, GPMI_NAND_GPMI_REGS_ADDR_RES_NAME))
                res->gpmi_regs = p;
        else if (!strcmp(res_name, GPMI_NAND_BCH_REGS_ADDR_RES_NAME))
                res->bch_regs = p;
        else
                dev_err(this->dev, "unknown resource name : %s\n", res_name);

        return 0;
}

static int acquire_bch_irq(struct gpmi_nand_data *this, irq_handler_t irq_h)
{
        struct platform_device *pdev = this->pdev;
        const char *res_name = GPMI_NAND_BCH_INTERRUPT_RES_NAME;
        struct resource *r;
        int err;

        r = platform_get_resource_byname(pdev, IORESOURCE_IRQ, res_name);
        if (!r) {
                dev_err(this->dev, "Can't get resource for %s\n", res_name);
                return -ENODEV;
        }

        err = devm_request_irq(this->dev, r->start, irq_h, 0, res_name, this);
        if (err)
                dev_err(this->dev, "error requesting BCH IRQ\n");

        return err;
}

static void release_dma_channels(struct gpmi_nand_data *this)
{
        unsigned int i;
        for (i = 0; i < DMA_CHANS; i++)
                if (this->dma_chans[i]) {
                        dma_release_channel(this->dma_chans[i]);
                        this->dma_chans[i] = NULL;
                }
}

static int acquire_dma_channels(struct gpmi_nand_data *this)
{
        struct platform_device *pdev = this->pdev;
        struct dma_chan *dma_chan;

        /* request dma channel */
        dma_chan = dma_request_slave_channel(&pdev->dev, "rx-tx");
        if (!dma_chan) {
                dev_err(this->dev, "Failed to request DMA channel.\n");
                goto acquire_err;
        }

        this->dma_chans[0] = dma_chan;
        return 0;

acquire_err:
        release_dma_channels(this);
        return -EINVAL;
}

static char *extra_clks_for_mx6q[GPMI_CLK_MAX] = {
        "gpmi_apb", "gpmi_bch", "gpmi_bch_apb", "per1_bch",
};

static int gpmi_get_clks(struct gpmi_nand_data *this)
{
        struct resources *r = &this->resources;
        char **extra_clks = NULL;
        struct clk *clk;
        int err, i;

        /* The main clock is stored in the first. */
        r->clock[0] = devm_clk_get(this->dev, "gpmi_io");
        if (IS_ERR(r->clock[0])) {
                err = PTR_ERR(r->clock[0]);
                goto err_clock;
        }

        /* Get extra clocks */
        if (GPMI_IS_MX6(this))
                extra_clks = extra_clks_for_mx6q;
        if (!extra_clks)
                return 0;

        for (i = 1; i < GPMI_CLK_MAX; i++) {
                if (extra_clks[i - 1] == NULL)
                        break;

                clk = devm_clk_get(this->dev, extra_clks[i - 1]);
                if (IS_ERR(clk)) {
                        err = PTR_ERR(clk);
                        goto err_clock;
                }

                r->clock[i] = clk;
        }

        if (GPMI_IS_MX6(this))
                /*
                 * Set the default value for the gpmi clock.
                 *
                 * If you want to use the ONFI nand which is in the
                 * Synchronous Mode, you should change the clock as you need.
                 */
                clk_set_rate(r->clock[0], 22000000);

        return 0;

err_clock:
        dev_dbg(this->dev, "failed in finding the clocks.\n");
        return err;
}

static int acquire_resources(struct gpmi_nand_data *this)
{
        int ret;

        ret = acquire_register_block(this, GPMI_NAND_GPMI_REGS_ADDR_RES_NAME);
        if (ret)
                goto exit_regs;

        ret = acquire_register_block(this, GPMI_NAND_BCH_REGS_ADDR_RES_NAME);
        if (ret)
                goto exit_regs;

        ret = acquire_bch_irq(this, bch_irq);
        if (ret)
                goto exit_regs;

        ret = acquire_dma_channels(this);
        if (ret)
                goto exit_regs;

        ret = gpmi_get_clks(this);
        if (ret)
                goto exit_clock;
        return 0;

exit_clock:
        release_dma_channels(this);
exit_regs:
        return ret;
}

static void release_resources(struct gpmi_nand_data *this)
{
        release_dma_channels(this);
}

static int init_hardware(struct gpmi_nand_data *this)
{
        int ret;

        /*
         * This structure contains the "safe" GPMI timing that should succeed
         * with any NAND Flash device
         * (although, with less-than-optimal performance).
         */
        struct nand_timing  safe_timing = {
                .data_setup_in_ns        = 80,
                .data_hold_in_ns         = 60,
                .address_setup_in_ns     = 25,
                .gpmi_sample_delay_in_ns =  6,
                .tREA_in_ns              = -1,
                .tRLOH_in_ns             = -1,
                .tRHOH_in_ns             = -1,
        };

        /* Initialize the hardwares. */
        ret = gpmi_init(this);
        if (ret)
                return ret;

        this->timing = safe_timing;
        return 0;
}

static int read_page_prepare(struct gpmi_nand_data *this,
                        void *destination, unsigned length,
                        void *alt_virt, dma_addr_t alt_phys, unsigned alt_size,
                        void **use_virt, dma_addr_t *use_phys)
{
        struct device *dev = this->dev;

        if (virt_addr_valid(destination)) {
                dma_addr_t dest_phys;

                dest_phys = dma_map_single(dev, destination,
                                                length, DMA_FROM_DEVICE);
                if (dma_mapping_error(dev, dest_phys)) {
                        if (alt_size < length) {
                                dev_err(dev, "Alternate buffer is too small\n");
                                return -ENOMEM;
                        }
                        goto map_failed;
                }
                *use_virt = destination;
                *use_phys = dest_phys;
                this->direct_dma_map_ok = true;
                return 0;
        }

map_failed:
        *use_virt = alt_virt;
        *use_phys = alt_phys;
        this->direct_dma_map_ok = false;
        return 0;
}

static inline void read_page_end(struct gpmi_nand_data *this,
                        void *destination, unsigned length,
                        void *alt_virt, dma_addr_t alt_phys, unsigned alt_size,
                        void *used_virt, dma_addr_t used_phys)
{
        if (this->direct_dma_map_ok)
                dma_unmap_single(this->dev, used_phys, length, DMA_FROM_DEVICE);
}

static inline void read_page_swap_end(struct gpmi_nand_data *this,
                        void *destination, unsigned length,
                        void *alt_virt, dma_addr_t alt_phys, unsigned alt_size,
                        void *used_virt, dma_addr_t used_phys)
{
        if (!this->direct_dma_map_ok)
                memcpy(destination, alt_virt, length);
}

static int send_page_prepare(struct gpmi_nand_data *this,
                        const void *source, unsigned length,
                        void *alt_virt, dma_addr_t alt_phys, unsigned alt_size,
                        const void **use_virt, dma_addr_t *use_phys)
{
        struct device *dev = this->dev;

        if (virt_addr_valid(source)) {
                dma_addr_t source_phys;

                source_phys = dma_map_single(dev, (void *)source, length,
                                                DMA_TO_DEVICE);
                if (dma_mapping_error(dev, source_phys)) {
                        if (alt_size < length) {
                                dev_err(dev, "Alternate buffer is too small\n");
                                return -ENOMEM;
                        }
                        goto map_failed;
                }
                *use_virt = source;
                *use_phys = source_phys;
                return 0;
        }
map_failed:
        /*
         * Copy the content of the source buffer into the alternate
         * buffer and set up the return values accordingly.
         */
        memcpy(alt_virt, source, length);

        *use_virt = alt_virt;
        *use_phys = alt_phys;
        return 0;
}

static void send_page_end(struct gpmi_nand_data *this,
                        const void *source, unsigned length,
                        void *alt_virt, dma_addr_t alt_phys, unsigned alt_size,
                        const void *used_virt, dma_addr_t used_phys)
{
        struct device *dev = this->dev;
        if (used_virt == source)
                dma_unmap_single(dev, used_phys, length, DMA_TO_DEVICE);
}

static void gpmi_free_dma_buffer(struct gpmi_nand_data *this)
{
        struct device *dev = this->dev;

        if (this->page_buffer_virt && virt_addr_valid(this->page_buffer_virt))
                dma_free_coherent(dev, this->page_buffer_size,
                                        this->page_buffer_virt,
                                        this->page_buffer_phys);
        kfree(this->cmd_buffer);
        kfree(this->data_buffer_dma);
        kfree(this->raw_buffer);

        this->cmd_buffer        = NULL;
        this->data_buffer_dma   = NULL;
        this->page_buffer_virt  = NULL;
        this->page_buffer_size  =  0;
}

/* Allocate the DMA buffers */
static int gpmi_alloc_dma_buffer(struct gpmi_nand_data *this)
{
        struct bch_geometry *geo = &this->bch_geometry;
        struct device *dev = this->dev;
        struct mtd_info *mtd = &this->mtd;

        /* [1] Allocate a command buffer. PAGE_SIZE is enough. */
        this->cmd_buffer = kzalloc(PAGE_SIZE, GFP_DMA | GFP_KERNEL);
        if (this->cmd_buffer == NULL)
                goto error_alloc;

        /*
         * [2] Allocate a read/write data buffer.
         *     The gpmi_alloc_dma_buffer can be called twice.
         *     We allocate a PAGE_SIZE length buffer if gpmi_alloc_dma_buffer
         *     is called before the nand_scan_ident; and we allocate a buffer
         *     of the real NAND page size when the gpmi_alloc_dma_buffer is
         *     called after the nand_scan_ident.
         */
        this->data_buffer_dma = kzalloc(mtd->writesize ?: PAGE_SIZE,
                                        GFP_DMA | GFP_KERNEL);
        if (this->data_buffer_dma == NULL)
                goto error_alloc;

        /*
         * [3] Allocate the page buffer.
         *
         * Both the payload buffer and the auxiliary buffer must appear on
         * 32-bit boundaries. We presume the size of the payload buffer is a
         * power of two and is much larger than four, which guarantees the
         * auxiliary buffer will appear on a 32-bit boundary.
         */
        this->page_buffer_size = geo->payload_size + geo->auxiliary_size;
        this->page_buffer_virt = dma_alloc_coherent(dev, this->page_buffer_size,
                                        &this->page_buffer_phys, GFP_DMA);
        if (!this->page_buffer_virt)
                goto error_alloc;

        this->raw_buffer = kzalloc(mtd->writesize + mtd->oobsize, GFP_KERNEL);
        if (!this->raw_buffer)
                goto error_alloc;

        /* Slice up the page buffer. */
        this->payload_virt = this->page_buffer_virt;
        this->payload_phys = this->page_buffer_phys;
        this->auxiliary_virt = this->payload_virt + geo->payload_size;
        this->auxiliary_phys = this->payload_phys + geo->payload_size;
        return 0;

error_alloc:
        gpmi_free_dma_buffer(this);
        return -ENOMEM;
}

static void gpmi_cmd_ctrl(struct mtd_info *mtd, int data, unsigned int ctrl)
{
        struct nand_chip *chip = mtd->priv;
        struct gpmi_nand_data *this = chip->priv;
        int ret;

        /*
         * Every operation begins with a command byte and a series of zero or
         * more address bytes. These are distinguished by either the Address
         * Latch Enable (ALE) or Command Latch Enable (CLE) signals being
         * asserted. When MTD is ready to execute the command, it will deassert
         * both latch enables.
         *
         * Rather than run a separate DMA operation for every single byte, we
         * queue them up and run a single DMA operation for the entire series
         * of command and data bytes. NAND_CMD_NONE means the END of the queue.
         */
        if ((ctrl & (NAND_ALE | NAND_CLE))) {
                if (data != NAND_CMD_NONE)
                        this->cmd_buffer[this->command_length++] = data;
                return;
        }

        if (!this->command_length)
                return;

        ret = gpmi_send_command(this);
        if (ret)
                dev_err(this->dev, "Chip: %u, Error %d\n",
                        this->current_chip, ret);

        this->command_length = 0;
}

static int gpmi_dev_ready(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd->priv;
        struct gpmi_nand_data *this = chip->priv;

        return gpmi_is_ready(this, this->current_chip);
}

static void gpmi_select_chip(struct mtd_info *mtd, int chipnr)
{
        struct nand_chip *chip = mtd->priv;
        struct gpmi_nand_data *this = chip->priv;

        if ((this->current_chip < 0) && (chipnr >= 0))
                gpmi_begin(this);
        else if ((this->current_chip >= 0) && (chipnr < 0))
                gpmi_end(this);

        this->current_chip = chipnr;
}

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

        dev_dbg(this->dev, "len is %d\n", len);
        this->upper_buf = buf;
        this->upper_len = len;

        gpmi_read_data(this);
}

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

        dev_dbg(this->dev, "len is %d\n", len);
        this->upper_buf = (uint8_t *)buf;
        this->upper_len = len;

        gpmi_send_data(this);
}

static uint8_t gpmi_read_byte(struct mtd_info *mtd)
{
        struct nand_chip *chip = mtd->priv;
        struct gpmi_nand_data *this = chip->priv;
        uint8_t *buf = this->data_buffer_dma;

        gpmi_read_buf(mtd, buf, 1);
        return buf[0];
}

/*
 * Handles block mark swapping.
 * It can be called in swapping the block mark, or swapping it back,
 * because the the operations are the same.
 */
static void block_mark_swapping(struct gpmi_nand_data *this,
                                void *payload, void *auxiliary)
{
        struct bch_geometry *nfc_geo = &this->bch_geometry;
        unsigned char *p;
        unsigned char *a;
        unsigned int  bit;
        unsigned char mask;
        unsigned char from_data;
        unsigned char from_oob;

        if (!this->swap_block_mark)
                return;

        /*
         * If control arrives here, we're swapping. Make some convenience
         * variables.
         */
        bit = nfc_geo->block_mark_bit_offset;
        p   = payload + nfc_geo->block_mark_byte_offset;
        a   = auxiliary;

        /*
         * Get the byte from the data area that overlays the block mark. Since
         * the ECC engine applies its own view to the bits in the page, the
         * physical block mark won't (in general) appear on a byte boundary in
         * the data.
         */
        from_data = (p[0] >> bit) | (p[1] << (8 - bit));

        /* Get the byte from the OOB. */
        from_oob = a[0];

        /* Swap them. */
        a[0] = from_data;

        mask = (0x1 << bit) - 1;
        p[0] = (p[0] & mask) | (from_oob << bit);

        mask = ~0 << bit;
        p[1] = (p[1] & mask) | (from_oob >> (8 - bit));
}

static int gpmi_ecc_read_page(struct mtd_info *mtd, struct nand_chip *chip,
                                uint8_t *buf, int oob_required, int page)
{
        struct gpmi_nand_data *this = chip->priv;
        struct bch_geometry *nfc_geo = &this->bch_geometry;
        void          *payload_virt;
        dma_addr_t    payload_phys;

        void          *auxiliary_virt;
        dma_addr_t    auxiliary_phys;
        unsigned int  i;
        unsigned char *status;
        unsigned int  max_bitflips = 0;
        int           ret;

        dev_dbg(this->dev, "page number is : %d\n", page);
        ret = read_page_prepare(this, buf, nfc_geo->payload_size,
                                        this->payload_virt, this->payload_phys,
                                        nfc_geo->payload_size,
                                        &payload_virt, &payload_phys);
        if (ret) {
                dev_err(this->dev, "Inadequate DMA buffer\n");
                ret = -ENOMEM;
                return ret;
        }
        auxiliary_virt = this->auxiliary_virt;
        auxiliary_phys = this->auxiliary_phys;

        /* go! */
        ret = gpmi_read_page(this, payload_phys, auxiliary_phys);
        read_page_end(this, buf, nfc_geo->payload_size,
                        this->payload_virt, this->payload_phys,
                        nfc_geo->payload_size,
                        payload_virt, payload_phys);
        if (ret) {
                dev_err(this->dev, "Error in ECC-based read: %d\n", ret);
                return ret;
        }

        /* handle the block mark swapping */
        block_mark_swapping(this, payload_virt, auxiliary_virt);

        /* Loop over status bytes, accumulating ECC status. */
        status = auxiliary_virt + nfc_geo->auxiliary_status_offset;

        for (i = 0; i < nfc_geo->ecc_chunk_count; i++, status++) {
                if ((*status == STATUS_GOOD) || (*status == STATUS_ERASED))
                        continue;

                if (*status == STATUS_UNCORRECTABLE) {
                        mtd->ecc_stats.failed++;
                        continue;
                }
                mtd->ecc_stats.corrected += *status;
                max_bitflips = max_t(unsigned int, max_bitflips, *status);
        }

        if (oob_required) {
                /*
                 * It's time to deliver the OOB bytes. See gpmi_ecc_read_oob()
                 * for details about our policy for delivering the OOB.
                 *
                 * We fill the caller's buffer with set bits, and then copy the
                 * block mark to th caller's buffer. Note that, if block mark
                 * swapping was necessary, it has already been done, so we can
                 * rely on the first byte of the auxiliary buffer to contain
                 * the block mark.
                 */
                memset(chip->oob_poi, ~0, mtd->oobsize);
                chip->oob_poi[0] = ((uint8_t *) auxiliary_virt)[0];
        }

        read_page_swap_end(this, buf, nfc_geo->payload_size,
                        this->payload_virt, this->payload_phys,
                        nfc_geo->payload_size,
                        payload_virt, payload_phys);

        return max_bitflips;
}

/* Fake a virtual small page for the subpage read */
static int gpmi_ecc_read_subpage(struct mtd_info *mtd, struct nand_chip *chip,
                        uint32_t offs, uint32_t len, uint8_t *buf, int page)
{
        struct gpmi_nand_data *this = chip->priv;
        void __iomem *bch_regs = this->resources.bch_regs;
        struct bch_geometry old_geo = this->bch_geometry;
        struct bch_geometry *geo = &this->bch_geometry;
        int size = chip->ecc.size; /* ECC chunk size */
        int meta, n, page_size;
        u32 r1_old, r2_old, r1_new, r2_new;
        unsigned int max_bitflips;
        int first, last, marker_pos;
        int ecc_parity_size;
        int col = 0;
        int old_swap_block_mark = this->swap_block_mark;

        /* The size of ECC parity */
        ecc_parity_size = geo->gf_len * geo->ecc_strength / 8;

        /* Align it with the chunk size */
        first = offs / size;
        last = (offs + len - 1) / size;

        if (this->swap_block_mark) {
                /*
                 * Find the chunk which contains the Block Marker.
                 * If this chunk is in the range of [first, last],
                 * we have to read out the whole page.
                 * Why? since we had swapped the data at the position of Block
                 * Marker to the metadata which is bound with the chunk 0.
                 */
                marker_pos = geo->block_mark_byte_offset / size;
                if (last >= marker_pos && first <= marker_pos) {
                        dev_dbg(this->dev,
                                "page:%d, first:%d, last:%d, marker at:%d\n",
                                page, first, last, marker_pos);
                        return gpmi_ecc_read_page(mtd, chip, buf, 0, page);
                }
        }

        meta = geo->metadata_size;
        if (first) {
                col = meta + (size + ecc_parity_size) * first;
                chip->cmdfunc(mtd, NAND_CMD_RNDOUT, col, -1);

                meta = 0;
                buf = buf + first * size;
        }

        /* Save the old environment */
        r1_old = r1_new = readl(bch_regs + HW_BCH_FLASH0LAYOUT0);
        r2_old = r2_new = readl(bch_regs + HW_BCH_FLASH0LAYOUT1);

        /* change the BCH registers and bch_geometry{} */
        n = last - first + 1;
        page_size = meta + (size + ecc_parity_size) * n;

        r1_new &= ~(BM_BCH_FLASH0LAYOUT0_NBLOCKS |
                        BM_BCH_FLASH0LAYOUT0_META_SIZE);
        r1_new |= BF_BCH_FLASH0LAYOUT0_NBLOCKS(n - 1)
                        | BF_BCH_FLASH0LAYOUT0_META_SIZE(meta);
        writel(r1_new, bch_regs + HW_BCH_FLASH0LAYOUT0);

        r2_new &= ~BM_BCH_FLASH0LAYOUT1_PAGE_SIZE;
        r2_new |= BF_BCH_FLASH0LAYOUT1_PAGE_SIZE(page_size);
        writel(r2_new, bch_regs + HW_BCH_FLASH0LAYOUT1);

        geo->ecc_chunk_count = n;
        geo->payload_size = n * size;
        geo->page_size = page_size;
        geo->auxiliary_status_offset = ALIGN(meta, 4);

        dev_dbg(this->dev, "page:%d(%d:%d)%d, chunk:(%d:%d), BCH PG size:%d\n",
                page, offs, len, col, first, n, page_size);

        /* Read the subpage now */
        this->swap_block_mark = false;
        max_bitflips = gpmi_ecc_read_page(mtd, chip, buf, 0, page);

        /* Restore */
        writel(r1_old, bch_regs + HW_BCH_FLASH0LAYOUT0);
        writel(r2_old, bch_regs + HW_BCH_FLASH0LAYOUT1);
        this->bch_geometry = old_geo;
        this->swap_block_mark = old_swap_block_mark;

        return max_bitflips;
}

static int gpmi_ecc_write_page(struct mtd_info *mtd, struct nand_chip *chip,
                                const uint8_t *buf, int oob_required)
{
        struct gpmi_nand_data *this = chip->priv;
        struct bch_geometry *nfc_geo = &this->bch_geometry;
        const void *payload_virt;
        dma_addr_t payload_phys;
        const void *auxiliary_virt;
        dma_addr_t auxiliary_phys;
        int        ret;

        dev_dbg(this->dev, "ecc write page.\n");
        if (this->swap_block_mark) {
                /*
                 * If control arrives here, we're doing block mark swapping.
                 * Since we can't modify the caller's buffers, we must copy them
                 * into our own.
                 */
                memcpy(this->payload_virt, buf, mtd->writesize);
                payload_virt = this->payload_virt;
                payload_phys = this->payload_phys;

                memcpy(this->auxiliary_virt, chip->oob_poi,
                                nfc_geo->auxiliary_size);
                auxiliary_virt = this->auxiliary_virt;
                auxiliary_phys = this->auxiliary_phys;

                /* Handle block mark swapping. */
                block_mark_swapping(this,
                                (void *)payload_virt, (void *)auxiliary_virt);
        } else {
                /*
                 * If control arrives here, we're not doing block mark swapping,
                 * so we can to try and use the caller's buffers.
                 */
                ret = send_page_prepare(this,
                                buf, mtd->writesize,
                                this->payload_virt, this->payload_phys,
                                nfc_geo->payload_size,
                                &payload_virt, &payload_phys);
                if (ret) {
                        dev_err(this->dev, "Inadequate payload DMA buffer\n");
                        return 0;
                }

                ret = send_page_prepare(this,
                                chip->oob_poi, mtd->oobsize,
                                this->auxiliary_virt, this->auxiliary_phys,
                                nfc_geo->auxiliary_size,
                                &auxiliary_virt, &auxiliary_phys);
                if (ret) {
                        dev_err(this->dev, "Inadequate auxiliary DMA buffer\n");
                        goto exit_auxiliary;
                }
        }

        /* Ask the NFC. */
        ret = gpmi_send_page(this, payload_phys, auxiliary_phys);
        if (ret)
                dev_err(this->dev, "Error in ECC-based write: %d\n", ret);

        if (!this->swap_block_mark) {
                send_page_end(this, chip->oob_poi, mtd->oobsize,
                                this->auxiliary_virt, this->auxiliary_phys,
                                nfc_geo->auxiliary_size,
                                auxiliary_virt, auxiliary_phys);
exit_auxiliary:
                send_page_end(this, buf, mtd->writesize,
                                this->payload_virt, this->payload_phys,
                                nfc_geo->payload_size,
                                payload_virt, payload_phys);
        }

        return 0;
}

/*
 * There are several places in this driver where we have to handle the OOB and
 * block marks. This is the function where things are the most complicated, so
 * this is where we try to explain it all. All the other places refer back to
 * here.
 *
 * These are the rules, in order of decreasing importance:
 *
 * 1) Nothing the caller does can be allowed to imperil the block mark.
 *
 * 2) In read operations, the first byte of the OOB we return must reflect the
 *    true state of the block mark, no matter where that block mark appears in
 *    the physical page.
 *
 * 3) ECC-based read operations return an OOB full of set bits (since we never
 *    allow ECC-based writes to the OOB, it doesn't matter what ECC-based reads
 *    return).
 *
 * 4) "Raw" read operations return a direct view of the physical bytes in the
 *    page, using the conventional definition of which bytes are data and which
 *    are OOB. This gives the caller a way to see the actual, physical bytes
 *    in the page, without the distortions applied by our ECC engine.
 *
 *
 * What we do for this specific read operation depends on two questions:
 *
 * 1) Are we doing a "raw" read, or an ECC-based read?
 *
 * 2) Are we using block mark swapping or transcription?
 *
 * There are four cases, illustrated by the following Karnaugh map:
 *
 *                    |           Raw           |         ECC-based       |
 *       -------------+-------------------------+-------------------------+
 *                    | Read the conventional   |                         |
 *                    | OOB at the end of the   |                         |
 *       Swapping     | page and return it. It  |                         |
 *                    | contains exactly what   |                         |
 *                    | we want.                | Read the block mark and |
 *       -------------+-------------------------+ return it in a buffer   |
 *                    | Read the conventional   | full of set bits.       |
 *                    | OOB at the end of the   |                         |
 *                    | page and also the block |                         |
 *       Transcribing | mark in the metadata.   |                         |
 *                    | Copy the block mark     |                         |
 *                    | into the first byte of  |                         |
 *                    | the OOB.                |                         |
 *       -------------+-------------------------+-------------------------+
 *
 * Note that we break rule #4 in the Transcribing/Raw case because we're not
 * giving an accurate view of the actual, physical bytes in the page (we're
 * overwriting the block mark). That's OK because it's more important to follow
 * rule #2.
 *
 * It turns out that knowing whether we want an "ECC-based" or "raw" read is not
 * easy. When reading a page, for example, the NAND Flash MTD code calls our
 * ecc.read_page or ecc.read_page_raw function. Thus, the fact that MTD wants an
 * ECC-based or raw view of the page is implicit in which function it calls
 * (there is a similar pair of ECC-based/raw functions for writing).
 */
static int gpmi_ecc_read_oob(struct mtd_info *mtd, struct nand_chip *chip,
                                int page)
{
        struct gpmi_nand_data *this = chip->priv;

        dev_dbg(this->dev, "page number is %d\n", page);
        /* clear the OOB buffer */
        memset(chip->oob_poi, ~0, mtd->oobsize);

        /* Read out the conventional OOB. */
        chip->cmdfunc(mtd, NAND_CMD_READ0, mtd->writesize, page);
        chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);

        /*
         * Now, we want to make sure the block mark is correct. In the
         * non-transcribing case (!GPMI_IS_MX23()), we already have it.
         * Otherwise, we need to explicitly read it.
         */
        if (GPMI_IS_MX23(this)) {
                /* Read the block mark into the first byte of the OOB buffer. */
                chip->cmdfunc(mtd, NAND_CMD_READ0, 0, page);
                chip->oob_poi[0] = chip->read_byte(mtd);
        }

        return 0;
}

static int
gpmi_ecc_write_oob(struct mtd_info *mtd, struct nand_chip *chip, int page)
{
        struct nand_oobfree *of = mtd->ecclayout->oobfree;
        int status = 0;

        /* Do we have available oob area? */
        if (!of->length)
                return -EPERM;

        if (!nand_is_slc(chip))
                return -EPERM;

        chip->cmdfunc(mtd, NAND_CMD_SEQIN, mtd->writesize + of->offset, page);
        chip->write_buf(mtd, chip->oob_poi + of->offset, of->length);
        chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);

        status = chip->waitfunc(mtd, chip);
        return status & NAND_STATUS_FAIL ? -EIO : 0;
}

/*
 * This function reads a NAND page without involving the ECC engine (no HW
 * ECC correction).
 * The tricky part in the GPMI/BCH controller is that it stores ECC bits
 * inline (interleaved with payload DATA), and do not align data chunk on
 * byte boundaries.
 * We thus need to take care moving the payload data and ECC bits stored in the
 * page into the provided buffers, which is why we're using gpmi_copy_bits.
 *
 * See set_geometry_by_ecc_info inline comments to have a full description
 * of the layout used by the GPMI controller.
 */
static int gpmi_ecc_read_page_raw(struct mtd_info *mtd,
                                  struct nand_chip *chip, uint8_t *buf,
                                  int oob_required, int page)
{
        struct gpmi_nand_data *this = chip->priv;
        struct bch_geometry *nfc_geo = &this->bch_geometry;
        int eccsize = nfc_geo->ecc_chunk_size;
        int eccbits = nfc_geo->ecc_strength * nfc_geo->gf_len;
        u8 *tmp_buf = this->raw_buffer;
        size_t src_bit_off;
        size_t oob_bit_off;
        size_t oob_byte_off;
        uint8_t *oob = chip->oob_poi;
        int step;

        chip->read_buf(mtd, tmp_buf,
                       mtd->writesize + mtd->oobsize);

        /*
         * If required, swap the bad block marker and the data stored in the
         * metadata section, so that we don't wrongly consider a block as bad.
         *
         * See the layout description for a detailed explanation on why this
         * is needed.
         */
        if (this->swap_block_mark) {
                u8 swap = tmp_buf[0];

                tmp_buf[0] = tmp_buf[mtd->writesize];
                tmp_buf[mtd->writesize] = swap;
        }

        /*
         * Copy the metadata section into the oob buffer (this section is
         * guaranteed to be aligned on a byte boundary).
         */
        if (oob_required)
                memcpy(oob, tmp_buf, nfc_geo->metadata_size);

        oob_bit_off = nfc_geo->metadata_size * 8;
        src_bit_off = oob_bit_off;

        /* Extract interleaved payload data and ECC bits */
        for (step = 0; step < nfc_geo->ecc_chunk_count; step++) {
                if (buf)
                        gpmi_copy_bits(buf, step * eccsize * 8,
                                       tmp_buf, src_bit_off,
                                       eccsize * 8);
                src_bit_off += eccsize * 8;

                /* Align last ECC block to align a byte boundary */
                if (step == nfc_geo->ecc_chunk_count - 1 &&
                    (oob_bit_off + eccbits) % 8)
                        eccbits += 8 - ((oob_bit_off + eccbits) % 8);

                if (oob_required)
                        gpmi_copy_bits(oob, oob_bit_off,
                                       tmp_buf, src_bit_off,
                                       eccbits);

                src_bit_off += eccbits;
                oob_bit_off += eccbits;
        }

        if (oob_required) {
                oob_byte_off = oob_bit_off / 8;

                if (oob_byte_off < mtd->oobsize)
                        memcpy(oob + oob_byte_off,
                               tmp_buf + mtd->writesize + oob_byte_off,
                               mtd->oobsize - oob_byte_off);
        }

        return 0;
}

/*
 * This function writes a NAND page without involving the ECC engine (no HW
 * ECC generation).
 * The tricky part in the GPMI/BCH controller is that it stores ECC bits
 * inline (interleaved with payload DATA), and do not align data chunk on
 * byte boundaries.
 * We thus need to take care moving the OOB area at the right place in the
 * final page, which is why we're using gpmi_copy_bits.
 *
 * See set_geometry_by_ecc_info inline comments to have a full description
 * of the layout used by the GPMI controller.
 */
static int gpmi_ecc_write_page_raw(struct mtd_info *mtd,
                                   struct nand_chip *chip,
                                   const uint8_t *buf,
                                   int oob_required)
{
        struct gpmi_nand_data *this = chip->priv;
        struct bch_geometry *nfc_geo = &this->bch_geometry;
        int eccsize = nfc_geo->ecc_chunk_size;
        int eccbits = nfc_geo->ecc_strength * nfc_geo->gf_len;
        u8 *tmp_buf = this->raw_buffer;
        uint8_t *oob = chip->oob_poi;
        size_t dst_bit_off;
        size_t oob_bit_off;
        size_t oob_byte_off;
        int step;

        /*
         * Initialize all bits to 1 in case we don't have a buffer for the
         * payload or oob data in order to leave unspecified bits of data
         * to their initial state.
         */
        if (!buf || !oob_required)
                memset(tmp_buf, 0xff, mtd->writesize + mtd->oobsize);

        /*
         * First copy the metadata section (stored in oob buffer) at the
         * beginning of the page, as imposed by the GPMI layout.
         */
        memcpy(tmp_buf, oob, nfc_geo->metadata_size);
        oob_bit_off = nfc_geo->metadata_size * 8;
        dst_bit_off = oob_bit_off;

        /* Interleave payload data and ECC bits */
        for (step = 0; step < nfc_geo->ecc_chunk_count; step++) {
                if (buf)
                        gpmi_copy_bits(tmp_buf, dst_bit_off,
                                       buf, step * eccsize * 8, eccsize * 8);
                dst_bit_off += eccsize * 8;

                /* Align last ECC block to align a byte boundary */
                if (step == nfc_geo->ecc_chunk_count - 1 &&
                    (oob_bit_off + eccbits) % 8)
                        eccbits += 8 - ((oob_bit_off + eccbits) % 8);

                if (oob_required)
                        gpmi_copy_bits(tmp_buf, dst_bit_off,
                                       oob, oob_bit_off, eccbits);

                dst_bit_off += eccbits;
                oob_bit_off += eccbits;
        }

        oob_byte_off = oob_bit_off / 8;

        if (oob_required && oob_byte_off < mtd->oobsize)
                memcpy(tmp_buf + mtd->writesize + oob_byte_off,
                       oob + oob_byte_off, mtd->oobsize - oob_byte_off);

        /*
         * If required, swap the bad block marker and the first byte of the
         * metadata section, so that we don't modify the bad block marker.
         *
         * See the layout description for a detailed explanation on why this
         * is needed.
         */
        if (this->swap_block_mark) {
                u8 swap = tmp_buf[0];

                tmp_buf[0] = tmp_buf[mtd->writesize];
                tmp_buf[mtd->writesize] = swap;
        }

        chip->write_buf(mtd, tmp_buf, mtd->writesize + mtd->oobsize);

        return 0;
}

static int gpmi_ecc_read_oob_raw(struct mtd_info *mtd, struct nand_chip *chip,
                                 int page)
{
        chip->cmdfunc(mtd, NAND_CMD_READ0, 0, page);

        return gpmi_ecc_read_page_raw(mtd, chip, NULL, 1, page);
}

static int gpmi_ecc_write_oob_raw(struct mtd_info *mtd, struct nand_chip *chip,
                                 int page)
{
        chip->cmdfunc(mtd, NAND_CMD_SEQIN, 0, page);

        return gpmi_ecc_write_page_raw(mtd, chip, NULL, 1);
}

static int gpmi_block_markbad(struct mtd_info *mtd, loff_t ofs)
{
        struct nand_chip *chip = mtd->priv;
        struct gpmi_nand_data *this = chip->priv;
        int ret = 0;
        uint8_t *block_mark;
        int column, page, status, chipnr;

        chipnr = (int)(ofs >> chip->chip_shift);
        chip->select_chip(mtd, chipnr);

        column = !GPMI_IS_MX23(this) ? mtd->writesize : 0;

        /* Write the block mark. */
        block_mark = this->data_buffer_dma;
        block_mark[0] = 0; /* bad block marker */

        /* Shift to get page */
        page = (int)(ofs >> chip->page_shift);

        chip->cmdfunc(mtd, NAND_CMD_SEQIN, column, page);
        chip->write_buf(mtd, block_mark, 1);
        chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);

        status = chip->waitfunc(mtd, chip);
        if (status & NAND_STATUS_FAIL)
                ret = -EIO;

        chip->select_chip(mtd, -1);

        return ret;
}

static int nand_boot_set_geometry(struct gpmi_nand_data *this)
{
        struct boot_rom_geometry *geometry = &this->rom_geometry;

        /*
         * Set the boot block stride size.
         *
         * In principle, we should be reading this from the OTP bits, since
         * that's where the ROM is going to get it. In fact, we don't have any
         * way to read the OTP bits, so we go with the default and hope for the
         * best.
         */
        geometry->stride_size_in_pages = 64;

        /*
         * Set the search area stride exponent.
         *
         * In principle, we should be reading this from the OTP bits, since
         * that's where the ROM is going to get it. In fact, we don't have any
         * way to read the OTP bits, so we go with the default and hope for the
         * best.
         */
        geometry->search_area_stride_exponent = 2;
        return 0;
}

static const char  *fingerprint = "STMP";
static int mx23_check_transcription_stamp(struct gpmi_nand_data *this)
{
        struct boot_rom_geometry *rom_geo = &this->rom_geometry;
        struct device *dev = this->dev;
        struct mtd_info *mtd = &this->mtd;
        struct nand_chip *chip = &this->nand;
        unsigned int search_area_size_in_strides;
        unsigned int stride;
        unsigned int page;
        uint8_t *buffer = chip->buffers->databuf;
        int saved_chip_number;
        int found_an_ncb_fingerprint = false;

        /* Compute the number of strides in a search area. */
        search_area_size_in_strides = 1 << rom_geo->search_area_stride_exponent;

        saved_chip_number = this->current_chip;
        chip->select_chip(mtd, 0);

        /*
         * Loop through the first search area, looking for the NCB fingerprint.
         */
        dev_dbg(dev, "Scanning for an NCB fingerprint...\n");

        for (stride = 0; stride < search_area_size_in_strides; stride++) {
                /* Compute the page addresses. */
                page = stride * rom_geo->stride_size_in_pages;

                dev_dbg(dev, "Looking for a fingerprint in page 0x%x\n", page);

                /*
                 * Read the NCB fingerprint. The fingerprint is four bytes long
                 * and starts in the 12th byte of the page.
                 */
                chip->cmdfunc(mtd, NAND_CMD_READ0, 12, page);
                chip->read_buf(mtd, buffer, strlen(fingerprint));

                /* Look for the fingerprint. */
                if (!memcmp(buffer, fingerprint, strlen(fingerprint))) {
                        found_an_ncb_fingerprint = true;
                        break;
                }

        }

        chip->select_chip(mtd, saved_chip_number);

        if (found_an_ncb_fingerprint)
                dev_dbg(dev, "\tFound a fingerprint\n");
        else
                dev_dbg(dev, "\tNo fingerprint found\n");
        return found_an_ncb_fingerprint;
}

/* Writes a transcription stamp. */
static int mx23_write_transcription_stamp(struct gpmi_nand_data *this)
{
        struct device *dev = this->dev;
        struct boot_rom_geometry *rom_geo = &this->rom_geometry;
        struct mtd_info *mtd = &this->mtd;
        struct nand_chip *chip = &this->nand;
        unsigned int block_size_in_pages;
        unsigned int search_area_size_in_strides;
        unsigned int search_area_size_in_pages;
        unsigned int search_area_size_in_blocks;
        unsigned int block;
        unsigned int stride;
        unsigned int page;
        uint8_t      *buffer = chip->buffers->databuf;
        int saved_chip_number;
        int status;

        /* Compute the search area geometry. */
        block_size_in_pages = mtd->erasesize / mtd->writesize;
        search_area_size_in_strides = 1 << rom_geo->search_area_stride_exponent;
        search_area_size_in_pages = search_area_size_in_strides *
                                        rom_geo->stride_size_in_pages;
        search_area_size_in_blocks =
                  (search_area_size_in_pages + (block_size_in_pages - 1)) /
                                    block_size_in_pages;

        dev_dbg(dev, "Search Area Geometry :\n");
        dev_dbg(dev, "\tin Blocks : %u\n", search_area_size_in_blocks);
        dev_dbg(dev, "\tin Strides: %u\n", search_area_size_in_strides);
        dev_dbg(dev, "\tin Pages  : %u\n", search_area_size_in_pages);

        /* Select chip 0. */
        saved_chip_number = this->current_chip;
        chip->select_chip(mtd, 0);

        /* Loop over blocks in the first search area, erasing them. */
        dev_dbg(dev, "Erasing the search area...\n");

        for (block = 0; block < search_area_size_in_blocks; block++) {
                /* Compute the page address. */
                page = block * block_size_in_pages;

                /* Erase this block. */
                dev_dbg(dev, "\tErasing block 0x%x\n", block);
                chip->cmdfunc(mtd, NAND_CMD_ERASE1, -1, page);
                chip->cmdfunc(mtd, NAND_CMD_ERASE2, -1, -1);

                /* Wait for the erase to finish. */
                status = chip->waitfunc(mtd, chip);
                if (status & NAND_STATUS_FAIL)
                        dev_err(dev, "[%s] Erase failed.\n", __func__);
        }

        /* Write the NCB fingerprint into the page buffer. */
        memset(buffer, ~0, mtd->writesize);
        memcpy(buffer + 12, fingerprint, strlen(fingerprint));

        /* Loop through the first search area, writing NCB fingerprints. */
        dev_dbg(dev, "Writing NCB fingerprints...\n");
        for (stride = 0; stride < search_area_size_in_strides; stride++) {
                /* Compute the page addresses. */
                page = stride * rom_geo->stride_size_in_pages;

                /* Write the first page of the current stride. */
                dev_dbg(dev, "Writing an NCB fingerprint in page 0x%x\n", page);
                chip->cmdfunc(mtd, NAND_CMD_SEQIN, 0x00, page);
                chip->ecc.write_page_raw(mtd, chip, buffer, 0);
                chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);

                /* Wait for the write to finish. */
                status = chip->waitfunc(mtd, chip);
                if (status & NAND_STATUS_FAIL)
                        dev_err(dev, "[%s] Write failed.\n", __func__);
        }

        /* Deselect chip 0. */
        chip->select_chip(mtd, saved_chip_number);
        return 0;
}

static int mx23_boot_init(struct gpmi_nand_data  *this)
{
        struct device *dev = this->dev;
        struct nand_chip *chip = &this->nand;
        struct mtd_info *mtd = &this->mtd;
        unsigned int block_count;
        unsigned int block;
        int     chipnr;
        int     page;
        loff_t  byte;
        uint8_t block_mark;
        int     ret = 0;

        /*
         * If control arrives here, we can't use block mark swapping, which
         * means we're forced to use transcription. First, scan for the
         * transcription stamp. If we find it, then we don't have to do
         * anything -- the block marks are already transcribed.
         */
        if (mx23_check_transcription_stamp(this))
                return 0;

        /*
         * If control arrives here, we couldn't find a transcription stamp, so
         * so we presume the block marks are in the conventional location.
         */
        dev_dbg(dev, "Transcribing bad block marks...\n");

        /* Compute the number of blocks in the entire medium. */
        block_count = chip->chipsize >> chip->phys_erase_shift;

        /*
         * Loop over all the blocks in the medium, transcribing block marks as
         * we go.
         */
        for (block = 0; block < block_count; block++) {
                /*
                 * Compute the chip, page and byte addresses for this block's
                 * conventional mark.
                 */
                chipnr = block >> (chip->chip_shift - chip->phys_erase_shift);
                page = block << (chip->phys_erase_shift - chip->page_shift);
                byte = block <<  chip->phys_erase_shift;

                /* Send the command to read the conventional block mark. */
                chip->select_chip(mtd, chipnr);
                chip->cmdfunc(mtd, NAND_CMD_READ0, mtd->writesize, page);
                block_mark = chip->read_byte(mtd);
                chip->select_chip(mtd, -1);

                /*
                 * Check if the block is marked bad. If so, we need to mark it
                 * again, but this time the result will be a mark in the
                 * location where we transcribe block marks.
                 */
                if (block_mark != 0xff) {
                        dev_dbg(dev, "Transcribing mark in block %u\n", block);
                        ret = chip->block_markbad(mtd, byte);
                        if (ret)
                                dev_err(dev,
                                        "Failed to mark block bad with ret %d\n",
                                        ret);
                }
        }

        /* Write the stamp that indicates we've transcribed the block marks. */
        mx23_write_transcription_stamp(this);
        return 0;
}

static int nand_boot_init(struct gpmi_nand_data  *this)
{
        nand_boot_set_geometry(this);

        /* This is ROM arch-specific initilization before the BBT scanning. */
        if (GPMI_IS_MX23(this))
                return mx23_boot_init(this);
        return 0;
}

static int gpmi_set_geometry(struct gpmi_nand_data *this)
{
        int ret;

        /* Free the temporary DMA memory for reading ID. */
        gpmi_free_dma_buffer(this);

        /* Set up the NFC geometry which is used by BCH. */
        ret = bch_set_geometry(this);
        if (ret) {
                dev_err(this->dev, "Error setting BCH geometry : %d\n", ret);
                return ret;
        }

        /* Alloc the new DMA buffers according to the pagesize and oobsize */
        return gpmi_alloc_dma_buffer(this);
}

static void gpmi_nand_exit(struct gpmi_nand_data *this)
{
        nand_release(&this->mtd);
        gpmi_free_dma_buffer(this);
}

static int gpmi_init_last(struct gpmi_nand_data *this)
{
        struct mtd_info *mtd = &this->mtd;
        struct nand_chip *chip = mtd->priv;
        struct nand_ecc_ctrl *ecc = &chip->ecc;
        struct bch_geometry *bch_geo = &this->bch_geometry;
        int ret;

        /* Set up the medium geometry */
        ret = gpmi_set_geometry(this);
        if (ret)
                return ret;

        /* Init the nand_ecc_ctrl{} */
        ecc->read_page  = gpmi_ecc_read_page;
        ecc->write_page = gpmi_ecc_write_page;
        ecc->read_oob   = gpmi_ecc_read_oob;
        ecc->write_oob  = gpmi_ecc_write_oob;
        ecc->read_page_raw = gpmi_ecc_read_page_raw;
        ecc->write_page_raw = gpmi_ecc_write_page_raw;
        ecc->read_oob_raw = gpmi_ecc_read_oob_raw;
        ecc->write_oob_raw = gpmi_ecc_write_oob_raw;
        ecc->mode       = NAND_ECC_HW;
        ecc->size       = bch_geo->ecc_chunk_size;
        ecc->strength   = bch_geo->ecc_strength;
        ecc->layout     = &gpmi_hw_ecclayout;

        /*
         * We only enable the subpage read when:
         *  (1) the chip is imx6, and
         *  (2) the size of the ECC parity is byte aligned.
         */
        if (GPMI_IS_MX6(this) &&
                ((bch_geo->gf_len * bch_geo->ecc_strength) % 8) == 0) {
                ecc->read_subpage = gpmi_ecc_read_subpage;
                chip->options |= NAND_SUBPAGE_READ;
        }

        /*
         * Can we enable the extra features? such as EDO or Sync mode.
         *
         * We do not check the return value now. That's means if we fail in
         * enable the extra features, we still can run in the normal way.
         */
        gpmi_extra_init(this);

        return 0;
}

static int gpmi_nand_init(struct gpmi_nand_data *this)
{
        struct mtd_info  *mtd = &this->mtd;
        struct nand_chip *chip = &this->nand;
        struct mtd_part_parser_data ppdata = {};
        int ret;

        /* init current chip */
        this->current_chip      = -1;

        /* init the MTD data structures */
        mtd->priv               = chip;
        mtd->name               = "gpmi-nand";
        mtd->owner              = THIS_MODULE;

        /* init the nand_chip{}, we don't support a 16-bit NAND Flash bus. */
        chip->priv              = this;
        chip->select_chip       = gpmi_select_chip;
        chip->cmd_ctrl          = gpmi_cmd_ctrl;
        chip->dev_ready         = gpmi_dev_ready;
        chip->read_byte         = gpmi_read_byte;
        chip->read_buf          = gpmi_read_buf;
        chip->write_buf         = gpmi_write_buf;
        chip->badblock_pattern  = &gpmi_bbt_descr;
        chip->block_markbad     = gpmi_block_markbad;
        chip->options           |= NAND_NO_SUBPAGE_WRITE;

        /* Set up swap_block_mark, must be set before the gpmi_set_geometry() */
        this->swap_block_mark = !GPMI_IS_MX23(this);

        if (of_get_nand_on_flash_bbt(this->dev->of_node)) {
                chip->bbt_options |= NAND_BBT_USE_FLASH | NAND_BBT_NO_OOB;

                if (of_property_read_bool(this->dev->of_node,
                                                "fsl,no-blockmark-swap"))
                        this->swap_block_mark = false;
        }
        dev_dbg(this->dev, "Blockmark swapping %sabled\n",
                this->swap_block_mark ? "en" : "dis");

        /*
         * Allocate a temporary DMA buffer for reading ID in the
         * nand_scan_ident().
         */
        this->bch_geometry.payload_size = 1024;
        this->bch_geometry.auxiliary_size = 128;
        ret = gpmi_alloc_dma_buffer(this);
        if (ret)
                goto err_out;

        ret = nand_scan_ident(mtd, GPMI_IS_MX6(this) ? 2 : 1, NULL);
        if (ret)
                goto err_out;

        ret = gpmi_init_last(this);
        if (ret)
                goto err_out;

        chip->options |= NAND_SKIP_BBTSCAN;
        ret = nand_scan_tail(mtd);
        if (ret)
                goto err_out;

        ret = nand_boot_init(this);
        if (ret)
                goto err_out;
        chip->scan_bbt(mtd);

        ppdata.of_node = this->pdev->dev.of_node;
        ret = mtd_device_parse_register(mtd, NULL, &ppdata, NULL, 0);
        if (ret)
                goto err_out;
        return 0;

err_out:
        gpmi_nand_exit(this);
        return ret;
}

static const struct of_device_id gpmi_nand_id_table[] = {
        {
                .compatible = "fsl,imx23-gpmi-nand",
                .data = &gpmi_devdata_imx23,
        }, {
                .compatible = "fsl,imx28-gpmi-nand",
                .data = &gpmi_devdata_imx28,
        }, {
                .compatible = "fsl,imx6q-gpmi-nand",
                .data = &gpmi_devdata_imx6q,
        }, {
                .compatible = "fsl,imx6sx-gpmi-nand",
                .data = &gpmi_devdata_imx6sx,
        }, {}
};
MODULE_DEVICE_TABLE(of, gpmi_nand_id_table);

static int gpmi_nand_probe(struct platform_device *pdev)
{
        struct gpmi_nand_data *this;
        const struct of_device_id *of_id;
        int ret;

        this = devm_kzalloc(&pdev->dev, sizeof(*this), GFP_KERNEL);
        if (!this)
                return -ENOMEM;

        of_id = of_match_device(gpmi_nand_id_table, &pdev->dev);
        if (of_id) {
                this->devdata = of_id->data;
        } else {
                dev_err(&pdev->dev, "Failed to find the right device id.\n");
                return -ENODEV;
        }

        platform_set_drvdata(pdev, this);
        this->pdev  = pdev;
        this->dev   = &pdev->dev;

        ret = acquire_resources(this);
        if (ret)
                goto exit_acquire_resources;

        ret = init_hardware(this);
        if (ret)
                goto exit_nfc_init;

        ret = gpmi_nand_init(this);
        if (ret)
                goto exit_nfc_init;

        dev_info(this->dev, "driver registered.\n");

        return 0;

exit_nfc_init:
        release_resources(this);
exit_acquire_resources:

        return ret;
}

static int gpmi_nand_remove(struct platform_device *pdev)
{
        struct gpmi_nand_data *this = platform_get_drvdata(pdev);

        gpmi_nand_exit(this);
        release_resources(this);
        return 0;
}

static struct platform_driver gpmi_nand_driver = {
        .driver = {
                .name = "gpmi-nand",
                .of_match_table = gpmi_nand_id_table,
        },
        .probe   = gpmi_nand_probe,
        .remove  = gpmi_nand_remove,
};
module_platform_driver(gpmi_nand_driver);

MODULE_AUTHOR("Freescale Semiconductor, Inc.");
MODULE_DESCRIPTION("i.MX GPMI NAND Flash Controller Driver");
MODULE_LICENSE("GPL");