// SPDX-License-Identifier: GPL-2.0
/*
 * Driver for Microchip 48L640 64 Kb SPI Serial EERAM
 *
 * Copyright Heiko Schocher <hs@denx.de>
 *
 * datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/20006055B.pdf
 *
 * we set continuous mode but reading/writing more bytes than
 * pagesize seems to bring chip into state where readden values
 * are wrong ... no idea why.
 *
 */
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/jiffies.h>
#include <linux/module.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/partitions.h>
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/sizes.h>
#include <linux/spi/flash.h>
#include <linux/spi/spi.h>
#include <linux/of.h>
#include <linux/string_choices.h>

struct mchp48_caps {
        unsigned int size;
        unsigned int page_size;
        bool auto_disable_wel;
};

struct mchp48l640_flash {
        struct spi_device       *spi;
        struct mutex            lock;
        struct mtd_info         mtd;
        const struct mchp48_caps        *caps;
};

#define MCHP48L640_CMD_WREN             0x06
#define MCHP48L640_CMD_WRDI             0x04
#define MCHP48L640_CMD_WRITE            0x02
#define MCHP48L640_CMD_READ             0x03
#define MCHP48L640_CMD_WRSR             0x01
#define MCHP48L640_CMD_RDSR             0x05

#define MCHP48L640_STATUS_RDY           0x01
#define MCHP48L640_STATUS_WEL           0x02
#define MCHP48L640_STATUS_BP0           0x04
#define MCHP48L640_STATUS_BP1           0x08
#define MCHP48L640_STATUS_SWM           0x10
#define MCHP48L640_STATUS_PRO           0x20
#define MCHP48L640_STATUS_ASE           0x40

#define MCHP48L640_TIMEOUT              100

#define MAX_CMD_SIZE                    0x10

#define to_mchp48l640_flash(x) container_of(x, struct mchp48l640_flash, mtd)

static int mchp48l640_mkcmd(struct mchp48l640_flash *flash, u8 cmd, loff_t addr, char *buf)
{
        buf[0] = cmd;
        buf[1] = addr >> 8;
        buf[2] = addr;

        return 3;
}

static int mchp48l640_read_status(struct mchp48l640_flash *flash, int *status)
{
        unsigned char cmd[2];
        int ret;

        cmd[0] = MCHP48L640_CMD_RDSR;
        cmd[1] = 0x00;
        mutex_lock(&flash->lock);
        ret = spi_write_then_read(flash->spi, &cmd[0], 1, &cmd[1], 1);
        mutex_unlock(&flash->lock);
        if (!ret)
                *status = cmd[1];
        dev_dbg(&flash->spi->dev, "read status ret: %d status: %x", ret, *status);

        return ret;
}

static int mchp48l640_waitforbit(struct mchp48l640_flash *flash, int bit, bool set)
{
        int ret, status;
        unsigned long deadline;

        deadline = jiffies + msecs_to_jiffies(MCHP48L640_TIMEOUT);
        do {
                ret = mchp48l640_read_status(flash, &status);
                dev_dbg(&flash->spi->dev, "read status ret: %d bit: %x %sset status: %x",
                        ret, bit, (set ? "" : "not"), status);
                if (ret)
                        return ret;

                if (set) {
                        if ((status & bit) == bit)
                                return 0;
                } else {
                        if ((status & bit) == 0)
                                return 0;
                }

                usleep_range(1000, 2000);
        } while (!time_after_eq(jiffies, deadline));

        dev_err(&flash->spi->dev, "Timeout waiting for bit %x %s set in status register.",
                bit, (set ? "" : "not"));
        return -ETIMEDOUT;
}

static int mchp48l640_write_prepare(struct mchp48l640_flash *flash, bool enable)
{
        unsigned char cmd[2];
        int ret;

        if (enable)
                cmd[0] = MCHP48L640_CMD_WREN;
        else
                cmd[0] = MCHP48L640_CMD_WRDI;

        mutex_lock(&flash->lock);
        ret = spi_write(flash->spi, cmd, 1);
        mutex_unlock(&flash->lock);

        if (ret)
                dev_err(&flash->spi->dev, "write %s failed ret: %d",
                        str_enable_disable(enable), ret);

        dev_dbg(&flash->spi->dev, "write %s success ret: %d",
                str_enable_disable(enable), ret);
        if (enable)
                return mchp48l640_waitforbit(flash, MCHP48L640_STATUS_WEL, true);

        return ret;
}

static int mchp48l640_set_mode(struct mchp48l640_flash *flash)
{
        unsigned char cmd[2];
        int ret;

        ret = mchp48l640_write_prepare(flash, true);
        if (ret)
                return ret;

        cmd[0] = MCHP48L640_CMD_WRSR;
        cmd[1] = MCHP48L640_STATUS_PRO;

        mutex_lock(&flash->lock);
        ret = spi_write(flash->spi, cmd, 2);
        mutex_unlock(&flash->lock);
        if (ret)
                dev_err(&flash->spi->dev, "Could not set continuous mode ret: %d", ret);

        return mchp48l640_waitforbit(flash, MCHP48L640_STATUS_PRO, true);
}

static int mchp48l640_wait_rdy(struct mchp48l640_flash *flash)
{
        return mchp48l640_waitforbit(flash, MCHP48L640_STATUS_RDY, false);
};

static int mchp48l640_write_page(struct mtd_info *mtd, loff_t to, size_t len,
                            size_t *retlen, const unsigned char *buf)
{
        struct mchp48l640_flash *flash = to_mchp48l640_flash(mtd);
        unsigned char *cmd;
        int ret;
        int cmdlen;

        cmd = kmalloc((3 + len), GFP_KERNEL | GFP_DMA);
        if (!cmd)
                return -ENOMEM;

        ret = mchp48l640_wait_rdy(flash);
        if (ret)
                goto fail;

        ret = mchp48l640_write_prepare(flash, true);
        if (ret)
                goto fail;

        mutex_lock(&flash->lock);
        cmdlen = mchp48l640_mkcmd(flash, MCHP48L640_CMD_WRITE, to, cmd);
        memcpy(&cmd[cmdlen], buf, len);
        ret = spi_write(flash->spi, cmd, cmdlen + len);
        mutex_unlock(&flash->lock);
        if (!ret)
                *retlen += len;
        else
                goto fail;

        if (flash->caps->auto_disable_wel) {
                ret = mchp48l640_waitforbit(flash, MCHP48L640_STATUS_WEL, false);
                if (ret)
                        goto fail;
        } else {
                ret = mchp48l640_write_prepare(flash, false);
                if (ret)
                        goto fail;
        }

        kfree(cmd);
        return 0;
fail:
        kfree(cmd);
        dev_err(&flash->spi->dev, "write fail with: %d", ret);
        return ret;
};

static int mchp48l640_write(struct mtd_info *mtd, loff_t to, size_t len,
                            size_t *retlen, const unsigned char *buf)
{
        struct mchp48l640_flash *flash = to_mchp48l640_flash(mtd);
        int ret;
        size_t wlen = 0;
        loff_t woff = to;
        size_t ws;
        size_t page_sz = flash->caps->page_size;

        /*
         * we set PRO bit (page rollover), but writing length > page size
         * does result in total chaos, so write in 32 byte chunks.
         */
        while (wlen < len) {
                ws = min((len - wlen), page_sz);
                ret = mchp48l640_write_page(mtd, woff, ws, retlen, &buf[wlen]);
                if (ret)
                        return ret;
                wlen += ws;
                woff += ws;
        }

        return 0;
}

static int mchp48l640_read_page(struct mtd_info *mtd, loff_t from, size_t len,
                           size_t *retlen, unsigned char *buf)
{
        struct mchp48l640_flash *flash = to_mchp48l640_flash(mtd);
        unsigned char *cmd;
        int ret;
        int cmdlen;

        cmd = kmalloc((3 + len), GFP_KERNEL | GFP_DMA);
        if (!cmd)
                return -ENOMEM;

        ret = mchp48l640_wait_rdy(flash);
        if (ret)
                goto fail;

        mutex_lock(&flash->lock);
        cmdlen = mchp48l640_mkcmd(flash, MCHP48L640_CMD_READ, from, cmd);
        ret = spi_write_then_read(flash->spi, cmd, cmdlen, buf, len);
        mutex_unlock(&flash->lock);
        if (!ret)
                *retlen += len;

        kfree(cmd);
        return ret;

fail:
        kfree(cmd);
        dev_err(&flash->spi->dev, "read fail with: %d", ret);
        return ret;
}

static int mchp48l640_read(struct mtd_info *mtd, loff_t from, size_t len,
                           size_t *retlen, unsigned char *buf)
{
        struct mchp48l640_flash *flash = to_mchp48l640_flash(mtd);
        int ret;
        size_t wlen = 0;
        loff_t woff = from;
        size_t ws;
        size_t page_sz = flash->caps->page_size;

        /*
         * we set PRO bit (page rollover), but if read length > page size
         * does result in total chaos in result ...
         */
        while (wlen < len) {
                ws = min((len - wlen), page_sz);
                ret = mchp48l640_read_page(mtd, woff, ws, retlen, &buf[wlen]);
                if (ret)
                        return ret;
                wlen += ws;
                woff += ws;
        }

        return 0;
};

static const struct mchp48_caps mchp48l640_caps = {
        .size = SZ_8K,
        .page_size = 32,
        .auto_disable_wel = true,
};

static const struct mchp48_caps mb85rs128ty_caps = {
        .size = SZ_16K,
        .page_size = 256,
        .auto_disable_wel = false,
};

static int mchp48l640_probe(struct spi_device *spi)
{
        struct mchp48l640_flash *flash;
        struct flash_platform_data *data;
        int err;
        int status;

        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);

        err = mchp48l640_read_status(flash, &status);
        if (err)
                return err;

        err = mchp48l640_set_mode(flash);
        if (err)
                return err;

        data = dev_get_platdata(&spi->dev);

        flash->caps = of_device_get_match_data(&spi->dev);
        if (!flash->caps)
                flash->caps = &mchp48l640_caps;

        mtd_set_of_node(&flash->mtd, spi->dev.of_node);
        flash->mtd.dev.parent   = &spi->dev;
        flash->mtd.type         = MTD_RAM;
        flash->mtd.flags        = MTD_CAP_RAM;
        flash->mtd.writesize    = flash->caps->page_size;
        flash->mtd.size         = flash->caps->size;
        flash->mtd._read        = mchp48l640_read;
        flash->mtd._write       = mchp48l640_write;

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

        return 0;
}

static void mchp48l640_remove(struct spi_device *spi)
{
        struct mchp48l640_flash *flash = spi_get_drvdata(spi);

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

static const struct of_device_id mchp48l640_of_table[] = {
        {
                .compatible = "microchip,48l640",
                .data = &mchp48l640_caps,
        },
        {
                .compatible = "fujitsu,mb85rs128ty",
                .data = &mb85rs128ty_caps,
        },
        {}
};
MODULE_DEVICE_TABLE(of, mchp48l640_of_table);

static const struct spi_device_id mchp48l640_spi_ids[] = {
        {
                .name = "48l640",
                .driver_data = (kernel_ulong_t)&mchp48l640_caps,
        },
        {
                .name = "mb85rs128ty",
                .driver_data = (kernel_ulong_t)&mb85rs128ty_caps,
        },
        {}
};
MODULE_DEVICE_TABLE(spi, mchp48l640_spi_ids);

static struct spi_driver mchp48l640_driver = {
        .driver = {
                .name   = "mchp48l640",
                .of_match_table = mchp48l640_of_table,
        },
        .probe          = mchp48l640_probe,
        .remove         = mchp48l640_remove,
        .id_table       = mchp48l640_spi_ids,
};

module_spi_driver(mchp48l640_driver);

MODULE_DESCRIPTION("MTD SPI driver for Microchip 48l640 EERAM chips");
MODULE_AUTHOR("Heiko Schocher <hs@denx.de>");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("spi:mchp48l640");