/*
 * SMI (Serial Memory Controller) device driver for Serial NOR Flash on
 * SPEAr platform
 * The serial nor interface is largely based on m25p80.c, however the SPI
 * interface has been replaced by SMI.
 *
 * Copyright © 2010 STMicroelectronics.
 * Ashish Priyadarshi
 * Shiraz Hashim <shiraz.linux.kernel@gmail.com>
 *
 * This file is licensed under the terms of the GNU General Public
 * License version 2. This program is licensed "as is" without any
 * warranty of any kind, whether express or implied.
 */

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/param.h>
#include <linux/platform_device.h>
#include <linux/pm.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/partitions.h>
#include <linux/mtd/spear_smi.h>
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/wait.h>
#include <linux/of.h>
#include <linux/of_address.h>

/* SMI clock rate */
#define SMI_MAX_CLOCK_FREQ      50000000 /* 50 MHz */

/* MAX time out to safely come out of a erase or write busy conditions */
#define SMI_PROBE_TIMEOUT       (HZ / 10)
#define SMI_MAX_TIME_OUT        (3 * HZ)

/* timeout for command completion */
#define SMI_CMD_TIMEOUT         (HZ / 10)

/* registers of smi */
#define SMI_CR1         0x0     /* SMI control register 1 */
#define SMI_CR2         0x4     /* SMI control register 2 */
#define SMI_SR          0x8     /* SMI status register */
#define SMI_TR          0xC     /* SMI transmit register */
#define SMI_RR          0x10    /* SMI receive register */

/* defines for control_reg 1 */
#define BANK_EN         (0xF << 0)      /* enables all banks */
#define DSEL_TIME       (0x6 << 4)      /* Deselect time 6 + 1 SMI_CK periods */
#define SW_MODE         (0x1 << 28)     /* enables SW Mode */
#define WB_MODE         (0x1 << 29)     /* Write Burst Mode */
#define FAST_MODE       (0x1 << 15)     /* Fast Mode */
#define HOLD1           (0x1 << 16)     /* Clock Hold period selection */

/* defines for control_reg 2 */
#define SEND            (0x1 << 7)      /* Send data */
#define TFIE            (0x1 << 8)      /* Transmission Flag Interrupt Enable */
#define WCIE            (0x1 << 9)      /* Write Complete Interrupt Enable */
#define RD_STATUS_REG   (0x1 << 10)     /* reads status reg */
#define WE              (0x1 << 11)     /* Write Enable */

#define TX_LEN_SHIFT    0
#define RX_LEN_SHIFT    4
#define BANK_SHIFT      12

/* defines for status register */
#define SR_WIP          0x1     /* Write in progress */
#define SR_WEL          0x2     /* Write enable latch */
#define SR_BP0          0x4     /* Block protect 0 */
#define SR_BP1          0x8     /* Block protect 1 */
#define SR_BP2          0x10    /* Block protect 2 */
#define SR_SRWD         0x80    /* SR write protect */
#define TFF             0x100   /* Transfer Finished Flag */
#define WCF             0x200   /* Transfer Finished Flag */
#define ERF1            0x400   /* Forbidden Write Request */
#define ERF2            0x800   /* Forbidden Access */

#define WM_SHIFT        12

/* flash opcodes */
#define OPCODE_RDID     0x9f    /* Read JEDEC ID */

/* Flash Device Ids maintenance section */

/* data structure to maintain flash ids from different vendors */
struct flash_device {
        char *name;
        u8 erase_cmd;
        u32 device_id;
        u32 pagesize;
        unsigned long sectorsize;
        unsigned long size_in_bytes;
};

#define FLASH_ID(n, es, id, psize, ssize, size) \
{                               \
        .name = n,              \
        .erase_cmd = es,        \
        .device_id = id,        \
        .pagesize = psize,      \
        .sectorsize = ssize,    \
        .size_in_bytes = size   \
}

static struct flash_device flash_devices[] = {
        FLASH_ID("st m25p16"     , 0xd8, 0x00152020, 0x100, 0x10000, 0x200000),
        FLASH_ID("st m25p32"     , 0xd8, 0x00162020, 0x100, 0x10000, 0x400000),
        FLASH_ID("st m25p64"     , 0xd8, 0x00172020, 0x100, 0x10000, 0x800000),
        FLASH_ID("st m25p128"    , 0xd8, 0x00182020, 0x100, 0x40000, 0x1000000),
        FLASH_ID("st m25p05"     , 0xd8, 0x00102020, 0x80 , 0x8000 , 0x10000),
        FLASH_ID("st m25p10"     , 0xd8, 0x00112020, 0x80 , 0x8000 , 0x20000),
        FLASH_ID("st m25p20"     , 0xd8, 0x00122020, 0x100, 0x10000, 0x40000),
        FLASH_ID("st m25p40"     , 0xd8, 0x00132020, 0x100, 0x10000, 0x80000),
        FLASH_ID("st m25p80"     , 0xd8, 0x00142020, 0x100, 0x10000, 0x100000),
        FLASH_ID("st m45pe10"    , 0xd8, 0x00114020, 0x100, 0x10000, 0x20000),
        FLASH_ID("st m45pe20"    , 0xd8, 0x00124020, 0x100, 0x10000, 0x40000),
        FLASH_ID("st m45pe40"    , 0xd8, 0x00134020, 0x100, 0x10000, 0x80000),
        FLASH_ID("st m45pe80"    , 0xd8, 0x00144020, 0x100, 0x10000, 0x100000),
        FLASH_ID("sp s25fl004"   , 0xd8, 0x00120201, 0x100, 0x10000, 0x80000),
        FLASH_ID("sp s25fl008"   , 0xd8, 0x00130201, 0x100, 0x10000, 0x100000),
        FLASH_ID("sp s25fl016"   , 0xd8, 0x00140201, 0x100, 0x10000, 0x200000),
        FLASH_ID("sp s25fl032"   , 0xd8, 0x00150201, 0x100, 0x10000, 0x400000),
        FLASH_ID("sp s25fl064"   , 0xd8, 0x00160201, 0x100, 0x10000, 0x800000),
        FLASH_ID("atmel 25f512"  , 0x52, 0x0065001F, 0x80 , 0x8000 , 0x10000),
        FLASH_ID("atmel 25f1024" , 0x52, 0x0060001F, 0x100, 0x8000 , 0x20000),
        FLASH_ID("atmel 25f2048" , 0x52, 0x0063001F, 0x100, 0x10000, 0x40000),
        FLASH_ID("atmel 25f4096" , 0x52, 0x0064001F, 0x100, 0x10000, 0x80000),
        FLASH_ID("atmel 25fs040" , 0xd7, 0x0004661F, 0x100, 0x10000, 0x80000),
        FLASH_ID("mac 25l512"    , 0xd8, 0x001020C2, 0x010, 0x10000, 0x10000),
        FLASH_ID("mac 25l1005"   , 0xd8, 0x001120C2, 0x010, 0x10000, 0x20000),
        FLASH_ID("mac 25l2005"   , 0xd8, 0x001220C2, 0x010, 0x10000, 0x40000),
        FLASH_ID("mac 25l4005"   , 0xd8, 0x001320C2, 0x010, 0x10000, 0x80000),
        FLASH_ID("mac 25l4005a"  , 0xd8, 0x001320C2, 0x010, 0x10000, 0x80000),
        FLASH_ID("mac 25l8005"   , 0xd8, 0x001420C2, 0x010, 0x10000, 0x100000),
        FLASH_ID("mac 25l1605"   , 0xd8, 0x001520C2, 0x100, 0x10000, 0x200000),
        FLASH_ID("mac 25l1605a"  , 0xd8, 0x001520C2, 0x010, 0x10000, 0x200000),
        FLASH_ID("mac 25l3205"   , 0xd8, 0x001620C2, 0x100, 0x10000, 0x400000),
        FLASH_ID("mac 25l3205a"  , 0xd8, 0x001620C2, 0x100, 0x10000, 0x400000),
        FLASH_ID("mac 25l6405"   , 0xd8, 0x001720C2, 0x100, 0x10000, 0x800000),
};

/* Define spear specific structures */

struct spear_snor_flash;

/**
 * struct spear_smi - Structure for SMI Device
 *
 * @clk: functional clock
 * @status: current status register of SMI.
 * @clk_rate: functional clock rate of SMI (default: SMI_MAX_CLOCK_FREQ)
 * @lock: lock to prevent parallel access of SMI.
 * @io_base: base address for registers of SMI.
 * @pdev: platform device
 * @cmd_complete: queue to wait for command completion of NOR-flash.
 * @num_flashes: number of flashes actually present on board.
 * @flash: separate structure for each Serial NOR-flash attached to SMI.
 */
struct spear_smi {
        struct clk *clk;
        u32 status;
        unsigned long clk_rate;
        struct mutex lock;
        void __iomem *io_base;
        struct platform_device *pdev;
        wait_queue_head_t cmd_complete;
        u32 num_flashes;
        struct spear_snor_flash *flash[MAX_NUM_FLASH_CHIP];
};

/**
 * struct spear_snor_flash - Structure for Serial NOR Flash
 *
 * @bank: Bank number(0, 1, 2, 3) for each NOR-flash.
 * @dev_id: Device ID of NOR-flash.
 * @lock: lock to manage flash read, write and erase operations
 * @mtd: MTD info for each NOR-flash.
 * @num_parts: Total number of partition in each bank of NOR-flash.
 * @parts: Partition info for each bank of NOR-flash.
 * @page_size: Page size of NOR-flash.
 * @base_addr: Base address of NOR-flash.
 * @erase_cmd: erase command may vary on different flash types
 * @fast_mode: flash supports read in fast mode
 */
struct spear_snor_flash {
        u32 bank;
        u32 dev_id;
        struct mutex lock;
        struct mtd_info mtd;
        u32 num_parts;
        struct mtd_partition *parts;
        u32 page_size;
        void __iomem *base_addr;
        u8 erase_cmd;
        u8 fast_mode;
};

static inline struct spear_snor_flash *get_flash_data(struct mtd_info *mtd)
{
        return container_of(mtd, struct spear_snor_flash, mtd);
}

/**
 * spear_smi_read_sr - Read status register of flash through SMI
 * @dev: structure of SMI information.
 * @bank: bank to which flash is connected
 *
 * This routine will return the status register of the flash chip present at the
 * given bank.
 */
static int spear_smi_read_sr(struct spear_smi *dev, u32 bank)
{
        int ret;
        u32 ctrlreg1;

        mutex_lock(&dev->lock);
        dev->status = 0; /* Will be set in interrupt handler */

        ctrlreg1 = readl(dev->io_base + SMI_CR1);
        /* program smi in hw mode */
        writel(ctrlreg1 & ~(SW_MODE | WB_MODE), dev->io_base + SMI_CR1);

        /* performing a rsr instruction in hw mode */
        writel((bank << BANK_SHIFT) | RD_STATUS_REG | TFIE,
                        dev->io_base + SMI_CR2);

        /* wait for tff */
        ret = wait_event_interruptible_timeout(dev->cmd_complete,
                        dev->status & TFF, SMI_CMD_TIMEOUT);

        /* copy dev->status (lower 16 bits) in order to release lock */
        if (ret > 0)
                ret = dev->status & 0xffff;
        else if (ret == 0)
                ret = -ETIMEDOUT;

        /* restore the ctrl regs state */
        writel(ctrlreg1, dev->io_base + SMI_CR1);
        writel(0, dev->io_base + SMI_CR2);
        mutex_unlock(&dev->lock);

        return ret;
}

/**
 * spear_smi_wait_till_ready - wait till flash is ready
 * @dev: structure of SMI information.
 * @bank: flash corresponding to this bank
 * @timeout: timeout for busy wait condition
 *
 * This routine checks for WIP (write in progress) bit in Status register
 * If successful the routine returns 0 else -EBUSY
 */
static int spear_smi_wait_till_ready(struct spear_smi *dev, u32 bank,
                unsigned long timeout)
{
        unsigned long finish;
        int status;

        finish = jiffies + timeout;
        do {
                status = spear_smi_read_sr(dev, bank);
                if (status < 0) {
                        if (status == -ETIMEDOUT)
                                continue; /* try till finish */
                        return status;
                } else if (!(status & SR_WIP)) {
                        return 0;
                }

                cond_resched();
        } while (!time_after_eq(jiffies, finish));

        dev_err(&dev->pdev->dev, "smi controller is busy, timeout\n");
        return -EBUSY;
}

/**
 * spear_smi_int_handler - SMI Interrupt Handler.
 * @irq: irq number
 * @dev_id: structure of SMI device, embedded in dev_id.
 *
 * The handler clears all interrupt conditions and records the status in
 * dev->status which is used by the driver later.
 */
static irqreturn_t spear_smi_int_handler(int irq, void *dev_id)
{
        u32 status = 0;
        struct spear_smi *dev = dev_id;

        status = readl(dev->io_base + SMI_SR);

        if (unlikely(!status))
                return IRQ_NONE;

        /* clear all interrupt conditions */
        writel(0, dev->io_base + SMI_SR);

        /* copy the status register in dev->status */
        dev->status |= status;

        /* send the completion */
        wake_up_interruptible(&dev->cmd_complete);

        return IRQ_HANDLED;
}

/**
 * spear_smi_hw_init - initializes the smi controller.
 * @dev: structure of smi device
 *
 * this routine initializes the smi controller wit the default values
 */
static void spear_smi_hw_init(struct spear_smi *dev)
{
        unsigned long rate = 0;
        u32 prescale = 0;
        u32 val;

        rate = clk_get_rate(dev->clk);

        /* functional clock of smi */
        prescale = DIV_ROUND_UP(rate, dev->clk_rate);

        /*
         * setting the standard values, fast mode, prescaler for
         * SMI_MAX_CLOCK_FREQ (50MHz) operation and bank enable
         */
        val = HOLD1 | BANK_EN | DSEL_TIME | (prescale << 8);

        mutex_lock(&dev->lock);
        /* clear all interrupt conditions */
        writel(0, dev->io_base + SMI_SR);

        writel(val, dev->io_base + SMI_CR1);
        mutex_unlock(&dev->lock);
}

/**
 * get_flash_index - match chip id from a flash list.
 * @flash_id: a valid nor flash chip id obtained from board.
 *
 * try to validate the chip id by matching from a list, if not found then simply
 * returns negative. In case of success returns index in to the flash devices
 * array.
 */
static int get_flash_index(u32 flash_id)
{
        int index;

        /* Matches chip-id to entire list of 'serial-nor flash' ids */
        for (index = 0; index < ARRAY_SIZE(flash_devices); index++) {
                if (flash_devices[index].device_id == flash_id)
                        return index;
        }

        /* Memory chip is not listed and not supported */
        return -ENODEV;
}

/**
 * spear_smi_write_enable - Enable the flash to do write operation
 * @dev: structure of SMI device
 * @bank: enable write for flash connected to this bank
 *
 * Set write enable latch with Write Enable command.
 * Returns 0 on success.
 */
static int spear_smi_write_enable(struct spear_smi *dev, u32 bank)
{
        int ret;
        u32 ctrlreg1;

        mutex_lock(&dev->lock);
        dev->status = 0; /* Will be set in interrupt handler */

        ctrlreg1 = readl(dev->io_base + SMI_CR1);
        /* program smi in h/w mode */
        writel(ctrlreg1 & ~SW_MODE, dev->io_base + SMI_CR1);

        /* give the flash, write enable command */
        writel((bank << BANK_SHIFT) | WE | TFIE, dev->io_base + SMI_CR2);

        ret = wait_event_interruptible_timeout(dev->cmd_complete,
                        dev->status & TFF, SMI_CMD_TIMEOUT);

        /* restore the ctrl regs state */
        writel(ctrlreg1, dev->io_base + SMI_CR1);
        writel(0, dev->io_base + SMI_CR2);

        if (ret == 0) {
                ret = -EIO;
                dev_err(&dev->pdev->dev,
                        "smi controller failed on write enable\n");
        } else if (ret > 0) {
                /* check whether write mode status is set for required bank */
                if (dev->status & (1 << (bank + WM_SHIFT)))
                        ret = 0;
                else {
                        dev_err(&dev->pdev->dev, "couldn't enable write\n");
                        ret = -EIO;
                }
        }

        mutex_unlock(&dev->lock);
        return ret;
}

static inline u32
get_sector_erase_cmd(struct spear_snor_flash *flash, u32 offset)
{
        u32 cmd;
        u8 *x = (u8 *)&cmd;

        x[0] = flash->erase_cmd;
        x[1] = offset >> 16;
        x[2] = offset >> 8;
        x[3] = offset;

        return cmd;
}

/**
 * spear_smi_erase_sector - erase one sector of flash
 * @dev: structure of SMI information
 * @command: erase command to be send
 * @bank: bank to which this command needs to be send
 * @bytes: size of command
 *
 * 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 spear_smi_erase_sector(struct spear_smi *dev,
                u32 bank, u32 command, u32 bytes)
{
        u32 ctrlreg1 = 0;
        int ret;

        ret = spear_smi_wait_till_ready(dev, bank, SMI_MAX_TIME_OUT);
        if (ret)
                return ret;

        ret = spear_smi_write_enable(dev, bank);
        if (ret)
                return ret;

        mutex_lock(&dev->lock);

        ctrlreg1 = readl(dev->io_base + SMI_CR1);
        writel((ctrlreg1 | SW_MODE) & ~WB_MODE, dev->io_base + SMI_CR1);

        /* send command in sw mode */
        writel(command, dev->io_base + SMI_TR);

        writel((bank << BANK_SHIFT) | SEND | TFIE | (bytes << TX_LEN_SHIFT),
                        dev->io_base + SMI_CR2);

        ret = wait_event_interruptible_timeout(dev->cmd_complete,
                        dev->status & TFF, SMI_CMD_TIMEOUT);

        if (ret == 0) {
                ret = -EIO;
                dev_err(&dev->pdev->dev, "sector erase failed\n");
        } else if (ret > 0)
                ret = 0; /* success */

        /* restore ctrl regs */
        writel(ctrlreg1, dev->io_base + SMI_CR1);
        writel(0, dev->io_base + SMI_CR2);

        mutex_unlock(&dev->lock);
        return ret;
}

/**
 * spear_mtd_erase - perform flash erase operation as requested by user
 * @mtd: Provides the memory characteristics
 * @e_info: Provides the erase information
 *
 * 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 spear_mtd_erase(struct mtd_info *mtd, struct erase_info *e_info)
{
        struct spear_snor_flash *flash = get_flash_data(mtd);
        struct spear_smi *dev = mtd->priv;
        u32 addr, command, bank;
        int len, ret;

        if (!flash || !dev)
                return -ENODEV;

        bank = flash->bank;
        if (bank > dev->num_flashes - 1) {
                dev_err(&dev->pdev->dev, "Invalid Bank Num");
                return -EINVAL;
        }

        addr = e_info->addr;
        len = e_info->len;

        mutex_lock(&flash->lock);

        /* now erase sectors in loop */
        while (len) {
                command = get_sector_erase_cmd(flash, addr);
                /* preparing the command for flash */
                ret = spear_smi_erase_sector(dev, bank, command, 4);
                if (ret) {
                        mutex_unlock(&flash->lock);
                        return ret;
                }
                addr += mtd->erasesize;
                len -= mtd->erasesize;
        }

        mutex_unlock(&flash->lock);

        return 0;
}

/**
 * spear_mtd_read - performs flash read operation as requested by the user
 * @mtd: MTD information of the memory bank
 * @from: Address from which to start read
 * @len: Number of bytes to be read
 * @retlen: Fills the Number of bytes actually read
 * @buf: Fills this after reading
 *
 * Read an address range from the flash chip. The address range
 * may be any size provided it is within the physical boundaries.
 * Returns 0 on success, non zero otherwise
 */
static int spear_mtd_read(struct mtd_info *mtd, loff_t from, size_t len,
                size_t *retlen, u8 *buf)
{
        struct spear_snor_flash *flash = get_flash_data(mtd);
        struct spear_smi *dev = mtd->priv;
        void __iomem *src;
        u32 ctrlreg1, val;
        int ret;

        if (!flash || !dev)
                return -ENODEV;

        if (flash->bank > dev->num_flashes - 1) {
                dev_err(&dev->pdev->dev, "Invalid Bank Num");
                return -EINVAL;
        }

        /* select address as per bank number */
        src = flash->base_addr + from;

        mutex_lock(&flash->lock);

        /* wait till previous write/erase is done. */
        ret = spear_smi_wait_till_ready(dev, flash->bank, SMI_MAX_TIME_OUT);
        if (ret) {
                mutex_unlock(&flash->lock);
                return ret;
        }

        mutex_lock(&dev->lock);
        /* put smi in hw mode not wbt mode */
        ctrlreg1 = val = readl(dev->io_base + SMI_CR1);
        val &= ~(SW_MODE | WB_MODE);
        if (flash->fast_mode)
                val |= FAST_MODE;

        writel(val, dev->io_base + SMI_CR1);

        memcpy_fromio(buf, src, len);

        /* restore ctrl reg1 */
        writel(ctrlreg1, dev->io_base + SMI_CR1);
        mutex_unlock(&dev->lock);

        *retlen = len;
        mutex_unlock(&flash->lock);

        return 0;
}

/*
 * The purpose of this function is to ensure a memcpy_toio() with byte writes
 * only. Its structure is inspired from the ARM implementation of _memcpy_toio()
 * which also does single byte writes but cannot be used here as this is just an
 * implementation detail and not part of the API. Not mentioning the comment
 * stating that _memcpy_toio() should be optimized.
 */
static void spear_smi_memcpy_toio_b(volatile void __iomem *dest,
                                    const void *src, size_t len)
{
        const unsigned char *from = src;

        while (len) {
                len--;
                writeb(*from, dest);
                from++;
                dest++;
        }
}

static inline int spear_smi_cpy_toio(struct spear_smi *dev, u32 bank,
                void __iomem *dest, const void *src, size_t len)
{
        int ret;
        u32 ctrlreg1;

        /* wait until finished previous write command. */
        ret = spear_smi_wait_till_ready(dev, bank, SMI_MAX_TIME_OUT);
        if (ret)
                return ret;

        /* put smi in write enable */
        ret = spear_smi_write_enable(dev, bank);
        if (ret)
                return ret;

        /* put smi in hw, write burst mode */
        mutex_lock(&dev->lock);

        ctrlreg1 = readl(dev->io_base + SMI_CR1);
        writel((ctrlreg1 | WB_MODE) & ~SW_MODE, dev->io_base + SMI_CR1);

        /*
         * In Write Burst mode (WB_MODE), the specs states that writes must be:
         * - incremental
         * - of the same size
         * The ARM implementation of memcpy_toio() will optimize the number of
         * I/O by using as much 4-byte writes as possible, surrounded by
         * 2-byte/1-byte access if:
         * - the destination is not 4-byte aligned
         * - the length is not a multiple of 4-byte.
         * Avoid this alternance of write access size by using our own 'byte
         * access' helper if at least one of the two conditions above is true.
         */
        if (IS_ALIGNED(len, sizeof(u32)) &&
            IS_ALIGNED((uintptr_t)dest, sizeof(u32)))
                memcpy_toio(dest, src, len);
        else
                spear_smi_memcpy_toio_b(dest, src, len);

        writel(ctrlreg1, dev->io_base + SMI_CR1);

        mutex_unlock(&dev->lock);
        return 0;
}

/**
 * spear_mtd_write - performs write operation as requested by the user.
 * @mtd: MTD information of the memory bank.
 * @to: Address to write.
 * @len: Number of bytes to be written.
 * @retlen: Number of bytes actually wrote.
 * @buf: Buffer from which the data to be taken.
 *
 * Write an address range to the flash chip. Data must be written in
 * flash_page_size chunks. The address range may be any size provided
 * it is within the physical boundaries.
 * Returns 0 on success, non zero otherwise
 */
static int spear_mtd_write(struct mtd_info *mtd, loff_t to, size_t len,
                size_t *retlen, const u8 *buf)
{
        struct spear_snor_flash *flash = get_flash_data(mtd);
        struct spear_smi *dev = mtd->priv;
        void __iomem *dest;
        u32 page_offset, page_size;
        int ret;

        if (!flash || !dev)
                return -ENODEV;

        if (flash->bank > dev->num_flashes - 1) {
                dev_err(&dev->pdev->dev, "Invalid Bank Num");
                return -EINVAL;
        }

        /* select address as per bank number */
        dest = flash->base_addr + to;
        mutex_lock(&flash->lock);

        page_offset = (u32)to % flash->page_size;

        /* do if all the bytes fit onto one page */
        if (page_offset + len <= flash->page_size) {
                ret = spear_smi_cpy_toio(dev, flash->bank, dest, buf, len);
                if (!ret)
                        *retlen += len;
        } else {
                u32 i;

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

                ret = spear_smi_cpy_toio(dev, flash->bank, dest, buf,
                                page_size);
                if (ret)
                        goto err_write;
                else
                        *retlen += page_size;

                /* write everything in pagesize 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;

                        ret = spear_smi_cpy_toio(dev, flash->bank, dest + i,
                                        buf + i, page_size);
                        if (ret)
                                break;
                        else
                                *retlen += page_size;
                }
        }

err_write:
        mutex_unlock(&flash->lock);

        return ret;
}

/**
 * spear_smi_probe_flash - Detects the NOR Flash chip.
 * @dev: structure of SMI information.
 * @bank: bank on which flash must be probed
 *
 * This routine will check whether there exists a flash chip on a given memory
 * bank ID.
 * Return index of the probed flash in flash devices structure
 */
static int spear_smi_probe_flash(struct spear_smi *dev, u32 bank)
{
        int ret;
        u32 val = 0;

        ret = spear_smi_wait_till_ready(dev, bank, SMI_PROBE_TIMEOUT);
        if (ret)
                return ret;

        mutex_lock(&dev->lock);

        dev->status = 0; /* Will be set in interrupt handler */
        /* put smi in sw mode */
        val = readl(dev->io_base + SMI_CR1);
        writel(val | SW_MODE, dev->io_base + SMI_CR1);

        /* send readid command in sw mode */
        writel(OPCODE_RDID, dev->io_base + SMI_TR);

        val = (bank << BANK_SHIFT) | SEND | (1 << TX_LEN_SHIFT) |
                (3 << RX_LEN_SHIFT) | TFIE;
        writel(val, dev->io_base + SMI_CR2);

        /* wait for TFF */
        ret = wait_event_interruptible_timeout(dev->cmd_complete,
                        dev->status & TFF, SMI_CMD_TIMEOUT);
        if (ret <= 0) {
                ret = -ENODEV;
                goto err_probe;
        }

        /* get memory chip id */
        val = readl(dev->io_base + SMI_RR);
        val &= 0x00ffffff;
        ret = get_flash_index(val);

err_probe:
        /* clear sw mode */
        val = readl(dev->io_base + SMI_CR1);
        writel(val & ~SW_MODE, dev->io_base + SMI_CR1);

        mutex_unlock(&dev->lock);
        return ret;
}


#ifdef CONFIG_OF
static int spear_smi_probe_config_dt(struct platform_device *pdev,
                                     struct device_node *np)
{
        struct spear_smi_plat_data *pdata = dev_get_platdata(&pdev->dev);
        struct device_node *pp;
        const __be32 *addr;
        u32 val;
        int len;
        int i = 0;

        if (!np)
                return -ENODEV;

        of_property_read_u32(np, "clock-rate", &val);
        pdata->clk_rate = val;

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

        /* Fill structs for each subnode (flash device) */
        for_each_child_of_node(np, pp) {
                pdata->np[i] = pp;

                /* Read base-addr and size from DT */
                addr = of_get_property(pp, "reg", &len);
                pdata->board_flash_info->mem_base = be32_to_cpup(&addr[0]);
                pdata->board_flash_info->size = be32_to_cpup(&addr[1]);

                if (of_get_property(pp, "st,smi-fast-mode", NULL))
                        pdata->board_flash_info->fast_mode = 1;

                i++;
        }

        pdata->num_flashes = i;

        return 0;
}
#else
static int spear_smi_probe_config_dt(struct platform_device *pdev,
                                     struct device_node *np)
{
        return -ENOSYS;
}
#endif

static int spear_smi_setup_banks(struct platform_device *pdev,
                                 u32 bank, struct device_node *np)
{
        struct spear_smi *dev = platform_get_drvdata(pdev);
        struct spear_smi_flash_info *flash_info;
        struct spear_smi_plat_data *pdata;
        struct spear_snor_flash *flash;
        struct mtd_partition *parts = NULL;
        int count = 0;
        int flash_index;
        int ret = 0;

        pdata = dev_get_platdata(&pdev->dev);
        if (bank > pdata->num_flashes - 1)
                return -EINVAL;

        flash_info = &pdata->board_flash_info[bank];
        if (!flash_info)
                return -ENODEV;

        flash = devm_kzalloc(&pdev->dev, sizeof(*flash), GFP_ATOMIC);
        if (!flash)
                return -ENOMEM;
        flash->bank = bank;
        flash->fast_mode = flash_info->fast_mode ? 1 : 0;
        mutex_init(&flash->lock);

        /* verify whether nor flash is really present on board */
        flash_index = spear_smi_probe_flash(dev, bank);
        if (flash_index < 0) {
                dev_info(&dev->pdev->dev, "smi-nor%d not found\n", bank);
                return flash_index;
        }
        /* map the memory for nor flash chip */
        flash->base_addr = devm_ioremap(&pdev->dev, flash_info->mem_base,
                                        flash_info->size);
        if (!flash->base_addr)
                return -EIO;

        dev->flash[bank] = flash;
        flash->mtd.priv = dev;

        if (flash_info->name)
                flash->mtd.name = flash_info->name;
        else
                flash->mtd.name = flash_devices[flash_index].name;

        flash->mtd.dev.parent = &pdev->dev;
        mtd_set_of_node(&flash->mtd, np);
        flash->mtd.type = MTD_NORFLASH;
        flash->mtd.writesize = 1;
        flash->mtd.flags = MTD_CAP_NORFLASH;
        flash->mtd.size = flash_info->size;
        flash->mtd.erasesize = flash_devices[flash_index].sectorsize;
        flash->page_size = flash_devices[flash_index].pagesize;
        flash->mtd.writebufsize = flash->page_size;
        flash->erase_cmd = flash_devices[flash_index].erase_cmd;
        flash->mtd._erase = spear_mtd_erase;
        flash->mtd._read = spear_mtd_read;
        flash->mtd._write = spear_mtd_write;
        flash->dev_id = flash_devices[flash_index].device_id;

        dev_info(&dev->pdev->dev, "mtd .name=%s .size=%llx(%lluM)\n",
                        flash->mtd.name, flash->mtd.size,
                        flash->mtd.size / (1024 * 1024));

        dev_info(&dev->pdev->dev, ".erasesize = 0x%x(%uK)\n",
                        flash->mtd.erasesize, flash->mtd.erasesize / 1024);

#ifndef CONFIG_OF
        if (flash_info->partitions) {
                parts = flash_info->partitions;
                count = flash_info->nr_partitions;
        }
#endif

        ret = mtd_device_register(&flash->mtd, parts, count);
        if (ret) {
                dev_err(&dev->pdev->dev, "Err MTD partition=%d\n", ret);
                return ret;
        }

        return 0;
}

/**
 * spear_smi_probe - Entry routine
 * @pdev: platform device structure
 *
 * This is the first routine which gets invoked during booting and does all
 * initialization/allocation work. The routine looks for available memory banks,
 * and do proper init for any found one.
 * Returns 0 on success, non zero otherwise
 */
static int spear_smi_probe(struct platform_device *pdev)
{
        struct device_node *np = pdev->dev.of_node;
        struct spear_smi_plat_data *pdata = NULL;
        struct spear_smi *dev;
        struct resource *smi_base;
        int irq, ret = 0;
        int i;

        if (np) {
                pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
                if (!pdata) {
                        ret = -ENOMEM;
                        goto err;
                }
                pdev->dev.platform_data = pdata;
                ret = spear_smi_probe_config_dt(pdev, np);
                if (ret) {
                        ret = -ENODEV;
                        dev_err(&pdev->dev, "no platform data\n");
                        goto err;
                }
        } else {
                pdata = dev_get_platdata(&pdev->dev);
                if (!pdata) {
                        ret = -ENODEV;
                        dev_err(&pdev->dev, "no platform data\n");
                        goto err;
                }
        }

        irq = platform_get_irq(pdev, 0);
        if (irq < 0) {
                ret = -ENODEV;
                goto err;
        }

        dev = devm_kzalloc(&pdev->dev, sizeof(*dev), GFP_ATOMIC);
        if (!dev) {
                ret = -ENOMEM;
                goto err;
        }

        smi_base = platform_get_resource(pdev, IORESOURCE_MEM, 0);

        dev->io_base = devm_ioremap_resource(&pdev->dev, smi_base);
        if (IS_ERR(dev->io_base)) {
                ret = PTR_ERR(dev->io_base);
                goto err;
        }

        dev->pdev = pdev;
        dev->clk_rate = pdata->clk_rate;

        if (dev->clk_rate > SMI_MAX_CLOCK_FREQ)
                dev->clk_rate = SMI_MAX_CLOCK_FREQ;

        dev->num_flashes = pdata->num_flashes;

        if (dev->num_flashes > MAX_NUM_FLASH_CHIP) {
                dev_err(&pdev->dev, "exceeding max number of flashes\n");
                dev->num_flashes = MAX_NUM_FLASH_CHIP;
        }

        dev->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(dev->clk)) {

                ret = PTR_ERR(dev->clk);
                goto err;
        }

        ret = clk_prepare_enable(dev->clk);
        if (ret)
                goto err;

        ret = devm_request_irq(&pdev->dev, irq, spear_smi_int_handler, 0,
                               pdev->name, dev);
        if (ret) {
                dev_err(&dev->pdev->dev, "SMI IRQ allocation failed\n");
                goto err_irq;
        }

        mutex_init(&dev->lock);
        init_waitqueue_head(&dev->cmd_complete);
        spear_smi_hw_init(dev);
        platform_set_drvdata(pdev, dev);

        /* loop for each serial nor-flash which is connected to smi */
        for (i = 0; i < dev->num_flashes; i++) {
                ret = spear_smi_setup_banks(pdev, i, pdata->np[i]);
                if (ret) {
                        dev_err(&dev->pdev->dev, "bank setup failed\n");
                        goto err_irq;
                }
        }

        return 0;

err_irq:
        clk_disable_unprepare(dev->clk);
err:
        return ret;
}

/**
 * spear_smi_remove - Exit routine
 * @pdev: platform device structure
 *
 * free all allocations and delete the partitions.
 */
static int spear_smi_remove(struct platform_device *pdev)
{
        struct spear_smi *dev;
        struct spear_snor_flash *flash;
        int ret, i;

        dev = platform_get_drvdata(pdev);
        if (!dev) {
                dev_err(&pdev->dev, "dev is null\n");
                return -ENODEV;
        }

        /* clean up for all nor flash */
        for (i = 0; i < dev->num_flashes; i++) {
                flash = dev->flash[i];
                if (!flash)
                        continue;

                /* clean up mtd stuff */
                ret = mtd_device_unregister(&flash->mtd);
                if (ret)
                        dev_err(&pdev->dev, "error removing mtd\n");
        }

        clk_disable_unprepare(dev->clk);

        return 0;
}

#ifdef CONFIG_PM_SLEEP
static int spear_smi_suspend(struct device *dev)
{
        struct spear_smi *sdev = dev_get_drvdata(dev);

        if (sdev && sdev->clk)
                clk_disable_unprepare(sdev->clk);

        return 0;
}

static int spear_smi_resume(struct device *dev)
{
        struct spear_smi *sdev = dev_get_drvdata(dev);
        int ret = -EPERM;

        if (sdev && sdev->clk)
                ret = clk_prepare_enable(sdev->clk);

        if (!ret)
                spear_smi_hw_init(sdev);
        return ret;
}
#endif

static SIMPLE_DEV_PM_OPS(spear_smi_pm_ops, spear_smi_suspend, spear_smi_resume);

#ifdef CONFIG_OF
static const struct of_device_id spear_smi_id_table[] = {
        { .compatible = "st,spear600-smi" },
        {}
};
MODULE_DEVICE_TABLE(of, spear_smi_id_table);
#endif

static struct platform_driver spear_smi_driver = {
        .driver = {
                .name = "smi",
                .bus = &platform_bus_type,
                .of_match_table = of_match_ptr(spear_smi_id_table),
                .pm = &spear_smi_pm_ops,
        },
        .probe = spear_smi_probe,
        .remove = spear_smi_remove,
};
module_platform_driver(spear_smi_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Ashish Priyadarshi, Shiraz Hashim <shiraz.linux.kernel@gmail.com>");
MODULE_DESCRIPTION("MTD SMI driver for serial nor flash chips");