/*
 * MTD SPI driver for ST M25Pxx (and similar) serial flash chips
 *
 * Author: Mike Lavender, mike@steroidmicros.com
 *
 * Copyright (c) 2005, Intec Automation Inc.
 *
 * Some parts are based on lart.c by Abraham Van Der Merwe
 *
 * Cleaned up and generalized based on mtd_dataflash.c
 *
 * This code is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 */

#include <linux/init.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/interrupt.h>
#include <linux/mutex.h>
#include <linux/math64.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/mod_devicetable.h>

#include <linux/mtd/mtd.h>
#include <linux/mtd/partitions.h>

#include <linux/spi/spi.h>
#include <linux/spi/flash.h>

/* Flash opcodes. */
#define OPCODE_WREN             0x06    /* Write enable */
#define OPCODE_RDSR             0x05    /* Read status register */
#define OPCODE_WRSR             0x01    /* Write status register 1 byte */
#define OPCODE_NORM_READ        0x03    /* Read data bytes (low frequency) */
#define OPCODE_FAST_READ        0x0b    /* Read data bytes (high frequency) */
#define OPCODE_PP               0x02    /* Page program (up to 256 bytes) */
#define OPCODE_BE_4K            0x20    /* Erase 4KiB block */
#define OPCODE_BE_32K           0x52    /* Erase 32KiB block */
#define OPCODE_CHIP_ERASE       0xc7    /* Erase whole flash chip */
#define OPCODE_SE               0xd8    /* Sector erase (usually 64KiB) */
#define OPCODE_RDID             0x9f    /* Read JEDEC ID */

/* Used for SST flashes only. */
#define OPCODE_BP               0x02    /* Byte program */
#define OPCODE_WRDI             0x04    /* Write disable */
#define OPCODE_AAI_WP           0xad    /* Auto address increment word program */

/* Status Register bits. */
#define SR_WIP                  1       /* Write in progress */
#define SR_WEL                  2       /* Write enable latch */
/* meaning of other SR_* bits may differ between vendors */
#define SR_BP0                  4       /* Block protect 0 */
#define SR_BP1                  8       /* Block protect 1 */
#define SR_BP2                  0x10    /* Block protect 2 */
#define SR_SRWD                 0x80    /* SR write protect */

/* Define max times to check status register before we give up. */
#define MAX_READY_WAIT_JIFFIES  (40 * HZ)       /* M25P16 specs 40s max chip erase */
#define MAX_CMD_SIZE            4

#ifdef CONFIG_M25PXX_USE_FAST_READ
#define OPCODE_READ     OPCODE_FAST_READ
#define FAST_READ_DUMMY_BYTE 1
#else
#define OPCODE_READ     OPCODE_NORM_READ
#define FAST_READ_DUMMY_BYTE 0
#endif

/****************************************************************************/

struct m25p {
        struct spi_device       *spi;
        struct mutex            lock;
        struct mtd_info         mtd;
        unsigned                partitioned:1;
        u16                     page_size;
        u16                     addr_width;
        u8                      erase_opcode;
        u8                      *command;
};

static inline struct m25p *mtd_to_m25p(struct mtd_info *mtd)
{
        return container_of(mtd, struct m25p, mtd);
}

/****************************************************************************/

/*
 * Internal helper functions
 */

/*
 * Read the status register, returning its value in the location
 * Return the status register value.
 * Returns negative if error occurred.
 */
static int read_sr(struct m25p *flash)
{
        ssize_t retval;
        u8 code = OPCODE_RDSR;
        u8 val;

        retval = spi_write_then_read(flash->spi, &code, 1, &val, 1);

        if (retval < 0) {
                dev_err(&flash->spi->dev, "error %d reading SR\n",
                                (int) retval);
                return retval;
        }

        return val;
}

/*
 * Write status register 1 byte
 * Returns negative if error occurred.
 */
static int write_sr(struct m25p *flash, u8 val)
{
        flash->command[0] = OPCODE_WRSR;
        flash->command[1] = val;

        return spi_write(flash->spi, flash->command, 2);
}

/*
 * Set write enable latch with Write Enable command.
 * Returns negative if error occurred.
 */
static inline int write_enable(struct m25p *flash)
{
        u8      code = OPCODE_WREN;

        return spi_write_then_read(flash->spi, &code, 1, NULL, 0);
}

/*
 * Send write disble instruction to the chip.
 */
static inline int write_disable(struct m25p *flash)
{
        u8      code = OPCODE_WRDI;

        return spi_write_then_read(flash->spi, &code, 1, NULL, 0);
}

/*
 * Service routine to read status register until ready, or timeout occurs.
 * Returns non-zero if error.
 */
static int wait_till_ready(struct m25p *flash)
{
        unsigned long deadline;
        int sr;

        deadline = jiffies + MAX_READY_WAIT_JIFFIES;

        do {
                if ((sr = read_sr(flash)) < 0)
                        break;
                else if (!(sr & SR_WIP))
                        return 0;

                cond_resched();

        } while (!time_after_eq(jiffies, deadline));

        return 1;
}

/*
 * Erase the whole flash memory
 *
 * Returns 0 if successful, non-zero otherwise.
 */
static int erase_chip(struct m25p *flash)
{
        DEBUG(MTD_DEBUG_LEVEL3, "%s: %s %lldKiB\n",
              dev_name(&flash->spi->dev), __func__,
              (long long)(flash->mtd.size >> 10));

        /* Wait until finished previous write command. */
        if (wait_till_ready(flash))
                return 1;

        /* Send write enable, then erase commands. */
        write_enable(flash);

        /* Set up command buffer. */
        flash->command[0] = OPCODE_CHIP_ERASE;

        spi_write(flash->spi, flash->command, 1);

        return 0;
}

static void m25p_addr2cmd(struct m25p *flash, unsigned int addr, u8 *cmd)
{
        /* opcode is in cmd[0] */
        cmd[1] = addr >> (flash->addr_width * 8 -  8);
        cmd[2] = addr >> (flash->addr_width * 8 - 16);
        cmd[3] = addr >> (flash->addr_width * 8 - 24);
}

static int m25p_cmdsz(struct m25p *flash)
{
        return 1 + flash->addr_width;
}

/*
 * Erase one sector of flash memory at offset ``offset'' which is any
 * address within the sector which should be erased.
 *
 * Returns 0 if successful, non-zero otherwise.
 */
static int erase_sector(struct m25p *flash, u32 offset)
{
        DEBUG(MTD_DEBUG_LEVEL3, "%s: %s %dKiB at 0x%08x\n",
                        dev_name(&flash->spi->dev), __func__,
                        flash->mtd.erasesize / 1024, offset);

        /* Wait until finished previous write command. */
        if (wait_till_ready(flash))
                return 1;

        /* Send write enable, then erase commands. */
        write_enable(flash);

        /* Set up command buffer. */
        flash->command[0] = flash->erase_opcode;
        m25p_addr2cmd(flash, offset, flash->command);

        spi_write(flash->spi, flash->command, m25p_cmdsz(flash));

        return 0;
}

/****************************************************************************/

/*
 * MTD implementation
 */

/*
 * Erase an address range on the flash chip.  The address range may extend
 * one or more erase sectors.  Return an error is there is a problem erasing.
 */
static int m25p80_erase(struct mtd_info *mtd, struct erase_info *instr)
{
        struct m25p *flash = mtd_to_m25p(mtd);
        u32 addr,len;
        uint32_t rem;

        DEBUG(MTD_DEBUG_LEVEL2, "%s: %s %s 0x%llx, len %lld\n",
              dev_name(&flash->spi->dev), __func__, "at",
              (long long)instr->addr, (long long)instr->len);

        /* sanity checks */
        if (instr->addr + instr->len > flash->mtd.size)
                return -EINVAL;
        div_u64_rem(instr->len, mtd->erasesize, &rem);
        if (rem)
                return -EINVAL;

        addr = instr->addr;
        len = instr->len;

        mutex_lock(&flash->lock);

        /* whole-chip erase? */
        if (len == flash->mtd.size) {
                if (erase_chip(flash)) {
                        instr->state = MTD_ERASE_FAILED;
                        mutex_unlock(&flash->lock);
                        return -EIO;
                }

        /* REVISIT in some cases we could speed up erasing large regions
         * by using OPCODE_SE instead of OPCODE_BE_4K.  We may have set up
         * to use "small sector erase", but that's not always optimal.
         */

        /* "sector"-at-a-time erase */
        } else {
                while (len) {
                        if (erase_sector(flash, addr)) {
                                instr->state = MTD_ERASE_FAILED;
                                mutex_unlock(&flash->lock);
                                return -EIO;
                        }

                        addr += mtd->erasesize;
                        len -= mtd->erasesize;
                }
        }

        mutex_unlock(&flash->lock);

        instr->state = MTD_ERASE_DONE;
        mtd_erase_callback(instr);

        return 0;
}

/*
 * Read an address range from the flash chip.  The address range
 * may be any size provided it is within the physical boundaries.
 */
static int m25p80_read(struct mtd_info *mtd, loff_t from, size_t len,
        size_t *retlen, u_char *buf)
{
        struct m25p *flash = mtd_to_m25p(mtd);
        struct spi_transfer t[2];
        struct spi_message m;

        DEBUG(MTD_DEBUG_LEVEL2, "%s: %s %s 0x%08x, len %zd\n",
                        dev_name(&flash->spi->dev), __func__, "from",
                        (u32)from, len);

        /* sanity checks */
        if (!len)
                return 0;

        if (from + len > flash->mtd.size)
                return -EINVAL;

        spi_message_init(&m);
        memset(t, 0, (sizeof t));

        /* NOTE:
         * OPCODE_FAST_READ (if available) is faster.
         * Should add 1 byte DUMMY_BYTE.
         */
        t[0].tx_buf = flash->command;
        t[0].len = m25p_cmdsz(flash) + FAST_READ_DUMMY_BYTE;
        spi_message_add_tail(&t[0], &m);

        t[1].rx_buf = buf;
        t[1].len = len;
        spi_message_add_tail(&t[1], &m);

        /* Byte count starts at zero. */
        if (retlen)
                *retlen = 0;

        mutex_lock(&flash->lock);

        /* Wait till previous write/erase is done. */
        if (wait_till_ready(flash)) {
                /* REVISIT status return?? */
                mutex_unlock(&flash->lock);
                return 1;
        }

        /* FIXME switch to OPCODE_FAST_READ.  It's required for higher
         * clocks; and at this writing, every chip this driver handles
         * supports that opcode.
         */

        /* Set up the write data buffer. */
        flash->command[0] = OPCODE_READ;
        m25p_addr2cmd(flash, from, flash->command);

        spi_sync(flash->spi, &m);

        *retlen = m.actual_length - m25p_cmdsz(flash) - FAST_READ_DUMMY_BYTE;

        mutex_unlock(&flash->lock);

        return 0;
}

/*
 * Write an address range to the flash chip.  Data must be written in
 * FLASH_PAGESIZE chunks.  The address range may be any size provided
 * it is within the physical boundaries.
 */
static int m25p80_write(struct mtd_info *mtd, loff_t to, size_t len,
        size_t *retlen, const u_char *buf)
{
        struct m25p *flash = mtd_to_m25p(mtd);
        u32 page_offset, page_size;
        struct spi_transfer t[2];
        struct spi_message m;

        DEBUG(MTD_DEBUG_LEVEL2, "%s: %s %s 0x%08x, len %zd\n",
                        dev_name(&flash->spi->dev), __func__, "to",
                        (u32)to, len);

        if (retlen)
                *retlen = 0;

        /* sanity checks */
        if (!len)
                return(0);

        if (to + len > flash->mtd.size)
                return -EINVAL;

        spi_message_init(&m);
        memset(t, 0, (sizeof t));

        t[0].tx_buf = flash->command;
        t[0].len = m25p_cmdsz(flash);
        spi_message_add_tail(&t[0], &m);

        t[1].tx_buf = buf;
        spi_message_add_tail(&t[1], &m);

        mutex_lock(&flash->lock);

        /* Wait until finished previous write command. */
        if (wait_till_ready(flash)) {
                mutex_unlock(&flash->lock);
                return 1;
        }

        write_enable(flash);

        /* Set up the opcode in the write buffer. */
        flash->command[0] = OPCODE_PP;
        m25p_addr2cmd(flash, to, flash->command);

        page_offset = to & (flash->page_size - 1);

        /* do all the bytes fit onto one page? */
        if (page_offset + len <= flash->page_size) {
                t[1].len = len;

                spi_sync(flash->spi, &m);

                *retlen = m.actual_length - m25p_cmdsz(flash);
        } else {
                u32 i;

                /* the size of data remaining on the first page */
                page_size = flash->page_size - page_offset;

                t[1].len = page_size;
                spi_sync(flash->spi, &m);

                *retlen = m.actual_length - m25p_cmdsz(flash);

                /* write everything in flash->page_size chunks */
                for (i = page_size; i < len; i += page_size) {
                        page_size = len - i;
                        if (page_size > flash->page_size)
                                page_size = flash->page_size;

                        /* write the next page to flash */
                        m25p_addr2cmd(flash, to + i, flash->command);

                        t[1].tx_buf = buf + i;
                        t[1].len = page_size;

                        wait_till_ready(flash);

                        write_enable(flash);

                        spi_sync(flash->spi, &m);

                        if (retlen)
                                *retlen += m.actual_length - m25p_cmdsz(flash);
                }
        }

        mutex_unlock(&flash->lock);

        return 0;
}

static int sst_write(struct mtd_info *mtd, loff_t to, size_t len,
                size_t *retlen, const u_char *buf)
{
        struct m25p *flash = mtd_to_m25p(mtd);
        struct spi_transfer t[2];
        struct spi_message m;
        size_t actual;
        int cmd_sz, ret;

        if (retlen)
                *retlen = 0;

        /* sanity checks */
        if (!len)
                return 0;

        if (to + len > flash->mtd.size)
                return -EINVAL;

        spi_message_init(&m);
        memset(t, 0, (sizeof t));

        t[0].tx_buf = flash->command;
        t[0].len = m25p_cmdsz(flash);
        spi_message_add_tail(&t[0], &m);

        t[1].tx_buf = buf;
        spi_message_add_tail(&t[1], &m);

        mutex_lock(&flash->lock);

        /* Wait until finished previous write command. */
        ret = wait_till_ready(flash);
        if (ret)
                goto time_out;

        write_enable(flash);

        actual = to % 2;
        /* Start write from odd address. */
        if (actual) {
                flash->command[0] = OPCODE_BP;
                m25p_addr2cmd(flash, to, flash->command);

                /* write one byte. */
                t[1].len = 1;
                spi_sync(flash->spi, &m);
                ret = wait_till_ready(flash);
                if (ret)
                        goto time_out;
                *retlen += m.actual_length - m25p_cmdsz(flash);
        }
        to += actual;

        flash->command[0] = OPCODE_AAI_WP;
        m25p_addr2cmd(flash, to, flash->command);

        /* Write out most of the data here. */
        cmd_sz = m25p_cmdsz(flash);
        for (; actual < len - 1; actual += 2) {
                t[0].len = cmd_sz;
                /* write two bytes. */
                t[1].len = 2;
                t[1].tx_buf = buf + actual;

                spi_sync(flash->spi, &m);
                ret = wait_till_ready(flash);
                if (ret)
                        goto time_out;
                *retlen += m.actual_length - cmd_sz;
                cmd_sz = 1;
                to += 2;
        }
        write_disable(flash);
        ret = wait_till_ready(flash);
        if (ret)
                goto time_out;

        /* Write out trailing byte if it exists. */
        if (actual != len) {
                write_enable(flash);
                flash->command[0] = OPCODE_BP;
                m25p_addr2cmd(flash, to, flash->command);
                t[0].len = m25p_cmdsz(flash);
                t[1].len = 1;
                t[1].tx_buf = buf + actual;

                spi_sync(flash->spi, &m);
                ret = wait_till_ready(flash);
                if (ret)
                        goto time_out;
                *retlen += m.actual_length - m25p_cmdsz(flash);
                write_disable(flash);
        }

time_out:
        mutex_unlock(&flash->lock);
        return ret;
}

/****************************************************************************/

/*
 * SPI device driver setup and teardown
 */

struct flash_info {
        /* JEDEC id zero means "no ID" (most older chips); otherwise it has
         * a high byte of zero plus three data bytes: the manufacturer id,
         * then a two byte device id.
         */
        u32             jedec_id;
        u16             ext_id;

        /* The size listed here is what works with OPCODE_SE, which isn't
         * necessarily called a "sector" by the vendor.
         */
        unsigned        sector_size;
        u16             n_sectors;

        u16             page_size;
        u16             addr_width;

        u16             flags;
#define SECT_4K         0x01            /* OPCODE_BE_4K works uniformly */
#define M25P_NO_ERASE   0x02            /* No erase command needed */
};

#define INFO(_jedec_id, _ext_id, _sector_size, _n_sectors, _flags)      \
        ((kernel_ulong_t)&(struct flash_info) {                         \
                .jedec_id = (_jedec_id),                                \
                .ext_id = (_ext_id),                                    \
                .sector_size = (_sector_size),                          \
                .n_sectors = (_n_sectors),                              \
                .page_size = 256,                                       \
                .addr_width = 3,                                        \
                .flags = (_flags),                                      \
        })

#define CAT25_INFO(_sector_size, _n_sectors, _page_size, _addr_width)   \
        ((kernel_ulong_t)&(struct flash_info) {                         \
                .sector_size = (_sector_size),                          \
                .n_sectors = (_n_sectors),                              \
                .page_size = (_page_size),                              \
                .addr_width = (_addr_width),                            \
                .flags = M25P_NO_ERASE,                                 \
        })

/* NOTE: double check command sets and memory organization when you add
 * more flash chips.  This current list focusses on newer chips, which
 * have been converging on command sets which including JEDEC ID.
 */
static const struct spi_device_id m25p_ids[] = {
        /* Atmel -- some are (confusingly) marketed as "DataFlash" */
        { "at25fs010",  INFO(0x1f6601, 0, 32 * 1024,   4, SECT_4K) },
        { "at25fs040",  INFO(0x1f6604, 0, 64 * 1024,   8, SECT_4K) },

        { "at25df041a", INFO(0x1f4401, 0, 64 * 1024,   8, SECT_4K) },
        { "at25df641",  INFO(0x1f4800, 0, 64 * 1024, 128, SECT_4K) },

        { "at26f004",   INFO(0x1f0400, 0, 64 * 1024,  8, SECT_4K) },
        { "at26df081a", INFO(0x1f4501, 0, 64 * 1024, 16, SECT_4K) },
        { "at26df161a", INFO(0x1f4601, 0, 64 * 1024, 32, SECT_4K) },
        { "at26df321",  INFO(0x1f4701, 0, 64 * 1024, 64, SECT_4K) },

        /* Macronix */
        { "mx25l4005a",  INFO(0xc22013, 0, 64 * 1024,   8, SECT_4K) },
        { "mx25l3205d",  INFO(0xc22016, 0, 64 * 1024,  64, 0) },
        { "mx25l6405d",  INFO(0xc22017, 0, 64 * 1024, 128, 0) },
        { "mx25l12805d", INFO(0xc22018, 0, 64 * 1024, 256, 0) },
        { "mx25l12855e", INFO(0xc22618, 0, 64 * 1024, 256, 0) },

        /* Spansion -- single (large) sector size only, at least
         * for the chips listed here (without boot sectors).
         */
        { "s25sl004a",  INFO(0x010212,      0,  64 * 1024,   8, 0) },
        { "s25sl008a",  INFO(0x010213,      0,  64 * 1024,  16, 0) },
        { "s25sl016a",  INFO(0x010214,      0,  64 * 1024,  32, 0) },
        { "s25sl032a",  INFO(0x010215,      0,  64 * 1024,  64, 0) },
        { "s25sl064a",  INFO(0x010216,      0,  64 * 1024, 128, 0) },
        { "s25sl12800", INFO(0x012018, 0x0300, 256 * 1024,  64, 0) },
        { "s25sl12801", INFO(0x012018, 0x0301,  64 * 1024, 256, 0) },
        { "s25fl129p0", INFO(0x012018, 0x4d00, 256 * 1024,  64, 0) },
        { "s25fl129p1", INFO(0x012018, 0x4d01,  64 * 1024, 256, 0) },

        /* SST -- large erase sizes are "overlays", "sectors" are 4K */
        { "sst25vf040b", INFO(0xbf258d, 0, 64 * 1024,  8, SECT_4K) },
        { "sst25vf080b", INFO(0xbf258e, 0, 64 * 1024, 16, SECT_4K) },
        { "sst25vf016b", INFO(0xbf2541, 0, 64 * 1024, 32, SECT_4K) },
        { "sst25vf032b", INFO(0xbf254a, 0, 64 * 1024, 64, SECT_4K) },
        { "sst25wf512",  INFO(0xbf2501, 0, 64 * 1024,  1, SECT_4K) },
        { "sst25wf010",  INFO(0xbf2502, 0, 64 * 1024,  2, SECT_4K) },
        { "sst25wf020",  INFO(0xbf2503, 0, 64 * 1024,  4, SECT_4K) },
        { "sst25wf040",  INFO(0xbf2504, 0, 64 * 1024,  8, SECT_4K) },

        /* ST Microelectronics -- newer production may have feature updates */
        { "m25p05",  INFO(0x202010,  0,  32 * 1024,   2, 0) },
        { "m25p10",  INFO(0x202011,  0,  32 * 1024,   4, 0) },
        { "m25p20",  INFO(0x202012,  0,  64 * 1024,   4, 0) },
        { "m25p40",  INFO(0x202013,  0,  64 * 1024,   8, 0) },
        { "m25p80",  INFO(0x202014,  0,  64 * 1024,  16, 0) },
        { "m25p16",  INFO(0x202015,  0,  64 * 1024,  32, 0) },
        { "m25p32",  INFO(0x202016,  0,  64 * 1024,  64, 0) },
        { "m25p64",  INFO(0x202017,  0,  64 * 1024, 128, 0) },
        { "m25p128", INFO(0x202018,  0, 256 * 1024,  64, 0) },

        { "m45pe10", INFO(0x204011,  0, 64 * 1024,    2, 0) },
        { "m45pe80", INFO(0x204014,  0, 64 * 1024,   16, 0) },
        { "m45pe16", INFO(0x204015,  0, 64 * 1024,   32, 0) },

        { "m25pe80", INFO(0x208014,  0, 64 * 1024, 16,       0) },
        { "m25pe16", INFO(0x208015,  0, 64 * 1024, 32, SECT_4K) },

        /* Winbond -- w25x "blocks" are 64K, "sectors" are 4KiB */
        { "w25x10", INFO(0xef3011, 0, 64 * 1024,  2,  SECT_4K) },
        { "w25x20", INFO(0xef3012, 0, 64 * 1024,  4,  SECT_4K) },
        { "w25x40", INFO(0xef3013, 0, 64 * 1024,  8,  SECT_4K) },
        { "w25x80", INFO(0xef3014, 0, 64 * 1024,  16, SECT_4K) },
        { "w25x16", INFO(0xef3015, 0, 64 * 1024,  32, SECT_4K) },
        { "w25x32", INFO(0xef3016, 0, 64 * 1024,  64, SECT_4K) },
        { "w25x64", INFO(0xef3017, 0, 64 * 1024, 128, SECT_4K) },

        /* Catalyst / On Semiconductor -- non-JEDEC */
        { "cat25c11", CAT25_INFO(  16, 8, 16, 1) },
        { "cat25c03", CAT25_INFO(  32, 8, 16, 2) },
        { "cat25c09", CAT25_INFO( 128, 8, 32, 2) },
        { "cat25c17", CAT25_INFO( 256, 8, 32, 2) },
        { "cat25128", CAT25_INFO(2048, 8, 64, 2) },
        { },
};
MODULE_DEVICE_TABLE(spi, m25p_ids);

static const struct spi_device_id *__devinit jedec_probe(struct spi_device *spi)
{
        int                     tmp;
        u8                      code = OPCODE_RDID;
        u8                      id[5];
        u32                     jedec;
        u16                     ext_jedec;
        struct flash_info       *info;

        /* JEDEC also defines an optional "extended device information"
         * string for after vendor-specific data, after the three bytes
         * we use here.  Supporting some chips might require using it.
         */
        tmp = spi_write_then_read(spi, &code, 1, id, 5);
        if (tmp < 0) {
                DEBUG(MTD_DEBUG_LEVEL0, "%s: error %d reading JEDEC ID\n",
                        dev_name(&spi->dev), tmp);
                return NULL;
        }
        jedec = id[0];
        jedec = jedec << 8;
        jedec |= id[1];
        jedec = jedec << 8;
        jedec |= id[2];

        /*
         * Some chips (like Numonyx M25P80) have JEDEC and non-JEDEC variants,
         * which depend on technology process. Officially RDID command doesn't
         * exist for non-JEDEC chips, but for compatibility they return ID 0.
         */
        if (jedec == 0)
                return NULL;

        ext_jedec = id[3] << 8 | id[4];

        for (tmp = 0; tmp < ARRAY_SIZE(m25p_ids) - 1; tmp++) {
                info = (void *)m25p_ids[tmp].driver_data;
                if (info->jedec_id == jedec) {
                        if (info->ext_id != 0 && info->ext_id != ext_jedec)
                                continue;
                        return &m25p_ids[tmp];
                }
        }
        return NULL;
}


/*
 * board specific setup should have ensured the SPI clock used here
 * matches what the READ command supports, at least until this driver
 * understands FAST_READ (for clocks over 25 MHz).
 */
static int __devinit m25p_probe(struct spi_device *spi)
{
        const struct spi_device_id      *id = spi_get_device_id(spi);
        struct flash_platform_data      *data;
        struct m25p                     *flash;
        struct flash_info               *info;
        unsigned                        i;

        /* Platform data helps sort out which chip type we have, as
         * well as how this board partitions it.  If we don't have
         * a chip ID, try the JEDEC id commands; they'll work for most
         * newer chips, even if we don't recognize the particular chip.
         */
        data = spi->dev.platform_data;
        if (data && data->type) {
                const struct spi_device_id *plat_id;

                for (i = 0; i < ARRAY_SIZE(m25p_ids) - 1; i++) {
                        plat_id = &m25p_ids[i];
                        if (strcmp(data->type, plat_id->name))
                                continue;
                        break;
                }

                if (plat_id)
                        id = plat_id;
                else
                        dev_warn(&spi->dev, "unrecognized id %s\n", data->type);
        }

        info = (void *)id->driver_data;

        if (info->jedec_id) {
                const struct spi_device_id *jid;

                jid = jedec_probe(spi);
                if (!jid) {
                        dev_info(&spi->dev, "non-JEDEC variant of %s\n",
                                 id->name);
                } else if (jid != id) {
                        /*
                         * JEDEC knows better, so overwrite platform ID. We
                         * can't trust partitions any longer, but we'll let
                         * mtd apply them anyway, since some partitions may be
                         * marked read-only, and we don't want to lose that
                         * information, even if it's not 100% accurate.
                         */
                        dev_warn(&spi->dev, "found %s, expected %s\n",
                                 jid->name, id->name);
                        id = jid;
                        info = (void *)jid->driver_data;
                }
        }

        flash = kzalloc(sizeof *flash, GFP_KERNEL);
        if (!flash)
                return -ENOMEM;
        flash->command = kmalloc(MAX_CMD_SIZE + FAST_READ_DUMMY_BYTE, GFP_KERNEL);
        if (!flash->command) {
                kfree(flash);
                return -ENOMEM;
        }

        flash->spi = spi;
        mutex_init(&flash->lock);
        dev_set_drvdata(&spi->dev, flash);

        /*
         * Atmel and SST serial flash tend to power
         * up with the software protection bits set
         */

        if (info->jedec_id >> 16 == 0x1f ||
            info->jedec_id >> 16 == 0xbf) {
                write_enable(flash);
                write_sr(flash, 0);
        }

        if (data && data->name)
                flash->mtd.name = data->name;
        else
                flash->mtd.name = dev_name(&spi->dev);

        flash->mtd.type = MTD_NORFLASH;
        flash->mtd.writesize = 1;
        flash->mtd.flags = MTD_CAP_NORFLASH;
        flash->mtd.size = info->sector_size * info->n_sectors;
        flash->mtd.erase = m25p80_erase;
        flash->mtd.read = m25p80_read;

        /* sst flash chips use AAI word program */
        if (info->jedec_id >> 16 == 0xbf)
                flash->mtd.write = sst_write;
        else
                flash->mtd.write = m25p80_write;

        /* prefer "small sector" erase if possible */
        if (info->flags & SECT_4K) {
                flash->erase_opcode = OPCODE_BE_4K;
                flash->mtd.erasesize = 4096;
        } else {
                flash->erase_opcode = OPCODE_SE;
                flash->mtd.erasesize = info->sector_size;
        }

        if (info->flags & M25P_NO_ERASE)
                flash->mtd.flags |= MTD_NO_ERASE;

        flash->mtd.dev.parent = &spi->dev;
        flash->page_size = info->page_size;
        flash->addr_width = info->addr_width;

        dev_info(&spi->dev, "%s (%lld Kbytes)\n", id->name,
                        (long long)flash->mtd.size >> 10);

        DEBUG(MTD_DEBUG_LEVEL2,
                "mtd .name = %s, .size = 0x%llx (%lldMiB) "
                        ".erasesize = 0x%.8x (%uKiB) .numeraseregions = %d\n",
                flash->mtd.name,
                (long long)flash->mtd.size, (long long)(flash->mtd.size >> 20),
                flash->mtd.erasesize, flash->mtd.erasesize / 1024,
                flash->mtd.numeraseregions);

        if (flash->mtd.numeraseregions)
                for (i = 0; i < flash->mtd.numeraseregions; i++)
                        DEBUG(MTD_DEBUG_LEVEL2,
                                "mtd.eraseregions[%d] = { .offset = 0x%llx, "
                                ".erasesize = 0x%.8x (%uKiB), "
                                ".numblocks = %d }\n",
                                i, (long long)flash->mtd.eraseregions[i].offset,
                                flash->mtd.eraseregions[i].erasesize,
                                flash->mtd.eraseregions[i].erasesize / 1024,
                                flash->mtd.eraseregions[i].numblocks);


        /* partitions should match sector boundaries; and it may be good to
         * use readonly partitions for writeprotected sectors (BP2..BP0).
         */
        if (mtd_has_partitions()) {
                struct mtd_partition    *parts = NULL;
                int                     nr_parts = 0;

                if (mtd_has_cmdlinepart()) {
                        static const char *part_probes[]
                                        = { "cmdlinepart", NULL, };

                        nr_parts = parse_mtd_partitions(&flash->mtd,
                                        part_probes, &parts, 0);
                }

                if (nr_parts <= 0 && data && data->parts) {
                        parts = data->parts;
                        nr_parts = data->nr_parts;
                }

                if (nr_parts > 0) {
                        for (i = 0; i < nr_parts; i++) {
                                DEBUG(MTD_DEBUG_LEVEL2, "partitions[%d] = "
                                        "{.name = %s, .offset = 0x%llx, "
                                                ".size = 0x%llx (%lldKiB) }\n",
                                        i, parts[i].name,
                                        (long long)parts[i].offset,
                                        (long long)parts[i].size,
                                        (long long)(parts[i].size >> 10));
                        }
                        flash->partitioned = 1;
                        return add_mtd_partitions(&flash->mtd, parts, nr_parts);
                }
        } else if (data && data->nr_parts)
                dev_warn(&spi->dev, "ignoring %d default partitions on %s\n",
                                data->nr_parts, data->name);

        return add_mtd_device(&flash->mtd) == 1 ? -ENODEV : 0;
}


static int __devexit m25p_remove(struct spi_device *spi)
{
        struct m25p     *flash = dev_get_drvdata(&spi->dev);
        int             status;

        /* Clean up MTD stuff. */
        if (mtd_has_partitions() && flash->partitioned)
                status = del_mtd_partitions(&flash->mtd);
        else
                status = del_mtd_device(&flash->mtd);
        if (status == 0) {
                kfree(flash->command);
                kfree(flash);
        }
        return 0;
}


static struct spi_driver m25p80_driver = {
        .driver = {
                .name   = "m25p80",
                .bus    = &spi_bus_type,
                .owner  = THIS_MODULE,
        },
        .id_table       = m25p_ids,
        .probe  = m25p_probe,
        .remove = __devexit_p(m25p_remove),

        /* REVISIT: many of these chips have deep power-down modes, which
         * should clearly be entered on suspend() to minimize power use.
         * And also when they're otherwise idle...
         */
};


static int __init m25p80_init(void)
{
        return spi_register_driver(&m25p80_driver);
}


static void __exit m25p80_exit(void)
{
        spi_unregister_driver(&m25p80_driver);
}


module_init(m25p80_init);
module_exit(m25p80_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Mike Lavender");
MODULE_DESCRIPTION("MTD SPI driver for ST M25Pxx flash chips");