// SPDX-License-Identifier: GPL-2.0-only
/*
 * sst25l.c
 *
 * Driver for SST25L SPI Flash chips
 *
 * Copyright © 2009 Bluewater Systems Ltd
 * Author: Andre Renaud <andre@bluewatersys.com>
 * Author: Ryan Mallon
 *
 * Based on m25p80.c
 */

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

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

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

/* Erases can take up to 3 seconds! */
#define MAX_READY_WAIT_JIFFIES  msecs_to_jiffies(3000)

#define SST25L_CMD_WRSR         0x01    /* Write status register */
#define SST25L_CMD_WRDI         0x04    /* Write disable */
#define SST25L_CMD_RDSR         0x05    /* Read status register */
#define SST25L_CMD_WREN         0x06    /* Write enable */
#define SST25L_CMD_READ         0x03    /* High speed read */

#define SST25L_CMD_EWSR         0x50    /* Enable write status register */
#define SST25L_CMD_SECTOR_ERASE 0x20    /* Erase sector */
#define SST25L_CMD_READ_ID      0x90    /* Read device ID */
#define SST25L_CMD_AAI_PROGRAM  0xaf    /* Auto address increment */

#define SST25L_STATUS_BUSY      (1 << 0)        /* Chip is busy */
#define SST25L_STATUS_WREN      (1 << 1)        /* Write enabled */
#define SST25L_STATUS_BP0       (1 << 2)        /* Block protection 0 */
#define SST25L_STATUS_BP1       (1 << 3)        /* Block protection 1 */

struct sst25l_flash {
        struct spi_device       *spi;
        struct mutex            lock;
        struct mtd_info         mtd;
};

struct flash_info {
        const char              *name;
        uint16_t                device_id;
        unsigned                page_size;
        unsigned                nr_pages;
        unsigned                erase_size;
};

#define to_sst25l_flash(x) container_of(x, struct sst25l_flash, mtd)

static struct flash_info sst25l_flash_info[] = {
        {"sst25lf020a", 0xbf43, 256, 1024, 4096},
        {"sst25lf040a", 0xbf44, 256, 2048, 4096},
};

static int sst25l_status(struct sst25l_flash *flash, int *status)
{
        struct spi_message m;
        struct spi_transfer t;
        unsigned char cmd_resp[2];
        int err;

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

        cmd_resp[0] = SST25L_CMD_RDSR;
        cmd_resp[1] = 0xff;
        t.tx_buf = cmd_resp;
        t.rx_buf = cmd_resp;
        t.len = sizeof(cmd_resp);
        spi_message_add_tail(&t, &m);
        err = spi_sync(flash->spi, &m);
        if (err < 0)
                return err;

        *status = cmd_resp[1];
        return 0;
}

static int sst25l_write_enable(struct sst25l_flash *flash, int enable)
{
        unsigned char command[2];
        int status, err;

        command[0] = enable ? SST25L_CMD_WREN : SST25L_CMD_WRDI;
        err = spi_write(flash->spi, command, 1);
        if (err)
                return err;

        command[0] = SST25L_CMD_EWSR;
        err = spi_write(flash->spi, command, 1);
        if (err)
                return err;

        command[0] = SST25L_CMD_WRSR;
        command[1] = enable ? 0 : SST25L_STATUS_BP0 | SST25L_STATUS_BP1;
        err = spi_write(flash->spi, command, 2);
        if (err)
                return err;

        if (enable) {
                err = sst25l_status(flash, &status);
                if (err)
                        return err;
                if (!(status & SST25L_STATUS_WREN))
                        return -EROFS;
        }

        return 0;
}

static int sst25l_wait_till_ready(struct sst25l_flash *flash)
{
        unsigned long deadline;
        int status, err;

        deadline = jiffies + MAX_READY_WAIT_JIFFIES;
        do {
                err = sst25l_status(flash, &status);
                if (err)
                        return err;
                if (!(status & SST25L_STATUS_BUSY))
                        return 0;

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

        return -ETIMEDOUT;
}

static int sst25l_erase_sector(struct sst25l_flash *flash, uint32_t offset)
{
        unsigned char command[4];
        int err;

        err = sst25l_write_enable(flash, 1);
        if (err)
                return err;

        command[0] = SST25L_CMD_SECTOR_ERASE;
        command[1] = offset >> 16;
        command[2] = offset >> 8;
        command[3] = offset;
        err = spi_write(flash->spi, command, 4);
        if (err)
                return err;

        err = sst25l_wait_till_ready(flash);
        if (err)
                return err;

        return sst25l_write_enable(flash, 0);
}

static int sst25l_erase(struct mtd_info *mtd, struct erase_info *instr)
{
        struct sst25l_flash *flash = to_sst25l_flash(mtd);
        uint32_t addr, end;
        int err;

        /* Sanity checks */
        if ((uint32_t)instr->len % mtd->erasesize)
                return -EINVAL;

        if ((uint32_t)instr->addr % mtd->erasesize)
                return -EINVAL;

        addr = instr->addr;
        end = addr + instr->len;

        mutex_lock(&flash->lock);

        err = sst25l_wait_till_ready(flash);
        if (err) {
                mutex_unlock(&flash->lock);
                return err;
        }

        while (addr < end) {
                err = sst25l_erase_sector(flash, addr);
                if (err) {
                        mutex_unlock(&flash->lock);
                        dev_err(&flash->spi->dev, "Erase failed\n");
                        return err;
                }

                addr += mtd->erasesize;
        }

        mutex_unlock(&flash->lock);

        return 0;
}

static int sst25l_read(struct mtd_info *mtd, loff_t from, size_t len,
                       size_t *retlen, unsigned char *buf)
{
        struct sst25l_flash *flash = to_sst25l_flash(mtd);
        struct spi_transfer transfer[2];
        struct spi_message message;
        unsigned char command[4];
        int ret;

        spi_message_init(&message);
        memset(&transfer, 0, sizeof(transfer));

        command[0] = SST25L_CMD_READ;
        command[1] = from >> 16;
        command[2] = from >> 8;
        command[3] = from;

        transfer[0].tx_buf = command;
        transfer[0].len = sizeof(command);
        spi_message_add_tail(&transfer[0], &message);

        transfer[1].rx_buf = buf;
        transfer[1].len = len;
        spi_message_add_tail(&transfer[1], &message);

        mutex_lock(&flash->lock);

        /* Wait for previous write/erase to complete */
        ret = sst25l_wait_till_ready(flash);
        if (ret) {
                mutex_unlock(&flash->lock);
                return ret;
        }

        spi_sync(flash->spi, &message);

        if (retlen && message.actual_length > sizeof(command))
                *retlen += message.actual_length - sizeof(command);

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

static int sst25l_write(struct mtd_info *mtd, loff_t to, size_t len,
                        size_t *retlen, const unsigned char *buf)
{
        struct sst25l_flash *flash = to_sst25l_flash(mtd);
        int i, j, ret, bytes, copied = 0;
        unsigned char command[5];

        if ((uint32_t)to % mtd->writesize)
                return -EINVAL;

        mutex_lock(&flash->lock);

        ret = sst25l_write_enable(flash, 1);
        if (ret)
                goto out;

        for (i = 0; i < len; i += mtd->writesize) {
                ret = sst25l_wait_till_ready(flash);
                if (ret)
                        goto out;

                /* Write the first byte of the page */
                command[0] = SST25L_CMD_AAI_PROGRAM;
                command[1] = (to + i) >> 16;
                command[2] = (to + i) >> 8;
                command[3] = (to + i);
                command[4] = buf[i];
                ret = spi_write(flash->spi, command, 5);
                if (ret < 0)
                        goto out;
                copied++;

                /*
                 * Write the remaining bytes using auto address
                 * increment mode
                 */
                bytes = min_t(uint32_t, mtd->writesize, len - i);
                for (j = 1; j < bytes; j++, copied++) {
                        ret = sst25l_wait_till_ready(flash);
                        if (ret)
                                goto out;

                        command[1] = buf[i + j];
                        ret = spi_write(flash->spi, command, 2);
                        if (ret)
                                goto out;
                }
        }

out:
        ret = sst25l_write_enable(flash, 0);

        if (retlen)
                *retlen = copied;

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

static struct flash_info *sst25l_match_device(struct spi_device *spi)
{
        struct flash_info *flash_info = NULL;
        struct spi_message m;
        struct spi_transfer t;
        unsigned char cmd_resp[6];
        int i, err;
        uint16_t id;

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

        cmd_resp[0] = SST25L_CMD_READ_ID;
        cmd_resp[1] = 0;
        cmd_resp[2] = 0;
        cmd_resp[3] = 0;
        cmd_resp[4] = 0xff;
        cmd_resp[5] = 0xff;
        t.tx_buf = cmd_resp;
        t.rx_buf = cmd_resp;
        t.len = sizeof(cmd_resp);
        spi_message_add_tail(&t, &m);
        err = spi_sync(spi, &m);
        if (err < 0) {
                dev_err(&spi->dev, "error reading device id\n");
                return NULL;
        }

        id = (cmd_resp[4] << 8) | cmd_resp[5];

        for (i = 0; i < ARRAY_SIZE(sst25l_flash_info); i++)
                if (sst25l_flash_info[i].device_id == id)
                        flash_info = &sst25l_flash_info[i];

        if (!flash_info)
                dev_err(&spi->dev, "unknown id %.4x\n", id);

        return flash_info;
}

static int sst25l_probe(struct spi_device *spi)
{
        struct flash_info *flash_info;
        struct sst25l_flash *flash;
        struct flash_platform_data *data;
        int ret;

        flash_info = sst25l_match_device(spi);
        if (!flash_info)
                return -ENODEV;

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

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

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

        flash->mtd.dev.parent   = &spi->dev;
        flash->mtd.type         = MTD_NORFLASH;
        flash->mtd.flags        = MTD_CAP_NORFLASH;
        flash->mtd.erasesize    = flash_info->erase_size;
        flash->mtd.writesize    = flash_info->page_size;
        flash->mtd.writebufsize = flash_info->page_size;
        flash->mtd.size         = flash_info->page_size * flash_info->nr_pages;
        flash->mtd._erase       = sst25l_erase;
        flash->mtd._read                = sst25l_read;
        flash->mtd._write       = sst25l_write;

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

        pr_debug("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);


        ret = mtd_device_register(&flash->mtd, data ? data->parts : NULL,
                                  data ? data->nr_parts : 0);
        if (ret)
                return -ENODEV;

        return 0;
}

static void sst25l_remove(struct spi_device *spi)
{
        struct sst25l_flash *flash = spi_get_drvdata(spi);

        WARN_ON(mtd_device_unregister(&flash->mtd));
}

static struct spi_driver sst25l_driver = {
        .driver = {
                .name   = "sst25l",
        },
        .probe          = sst25l_probe,
        .remove         = sst25l_remove,
};

module_spi_driver(sst25l_driver);

MODULE_DESCRIPTION("MTD SPI driver for SST25L Flash chips");
MODULE_AUTHOR("Andre Renaud <andre@bluewatersys.com>, "
              "Ryan Mallon");
MODULE_LICENSE("GPL");