// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * OPAL PNOR flash MTD abstraction
 *
 * Copyright IBM 2015
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/platform_device.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/partitions.h>

#include <linux/debugfs.h>
#include <linux/seq_file.h>

#include <asm/opal.h>


/*
 * This driver creates the a Linux MTD abstraction for platform PNOR flash
 * backed by OPAL calls
 */

struct powernv_flash {
        struct mtd_info mtd;
        u32 id;
};

enum flash_op {
        FLASH_OP_READ,
        FLASH_OP_WRITE,
        FLASH_OP_ERASE,
};

/*
 * Don't return -ERESTARTSYS if we can't get a token, the MTD core
 * might have split up the call from userspace and called into the
 * driver more than once, we'll already have done some amount of work.
 */
static int powernv_flash_async_op(struct mtd_info *mtd, enum flash_op op,
                loff_t offset, size_t len, size_t *retlen, u_char *buf)
{
        struct powernv_flash *info = (struct powernv_flash *)mtd->priv;
        struct device *dev = &mtd->dev;
        int token;
        struct opal_msg msg;
        int rc;

        dev_dbg(dev, "%s(op=%d, offset=0x%llx, len=%zu)\n",
                        __func__, op, offset, len);

        token = opal_async_get_token_interruptible();
        if (token < 0) {
                if (token != -ERESTARTSYS)
                        dev_err(dev, "Failed to get an async token\n");
                else
                        token = -EINTR;
                return token;
        }

        switch (op) {
        case FLASH_OP_READ:
                rc = opal_flash_read(info->id, offset, __pa(buf), len, token);
                break;
        case FLASH_OP_WRITE:
                rc = opal_flash_write(info->id, offset, __pa(buf), len, token);
                break;
        case FLASH_OP_ERASE:
                rc = opal_flash_erase(info->id, offset, len, token);
                break;
        default:
                WARN_ON_ONCE(1);
                opal_async_release_token(token);
                return -EIO;
        }

        if (rc == OPAL_ASYNC_COMPLETION) {
                rc = opal_async_wait_response_interruptible(token, &msg);
                if (rc) {
                        /*
                         * If we return the mtd core will free the
                         * buffer we've just passed to OPAL but OPAL
                         * will continue to read or write from that
                         * memory.
                         * It may be tempting to ultimately return 0
                         * if we're doing a read or a write since we
                         * are going to end up waiting until OPAL is
                         * done. However, because the MTD core sends
                         * us the userspace request in chunks, we need
                         * it to know we've been interrupted.
                         */
                        rc = -EINTR;
                        if (opal_async_wait_response(token, &msg))
                                dev_err(dev, "opal_async_wait_response() failed\n");
                        goto out;
                }
                rc = opal_get_async_rc(msg);
        }

        /*
         * OPAL does mutual exclusion on the flash, it will return
         * OPAL_BUSY.
         * During firmware updates by the service processor OPAL may
         * be (temporarily) prevented from accessing the flash, in
         * this case OPAL will also return OPAL_BUSY.
         * Both cases aren't errors exactly but the flash could have
         * changed, userspace should be informed.
         */
        if (rc != OPAL_SUCCESS && rc != OPAL_BUSY)
                dev_err(dev, "opal_flash_async_op(op=%d) failed (rc %d)\n",
                                op, rc);

        if (rc == OPAL_SUCCESS && retlen)
                *retlen = len;

        rc = opal_error_code(rc);
out:
        opal_async_release_token(token);
        return rc;
}

/**
 * powernv_flash_read
 * @mtd: the device
 * @from: the offset to read from
 * @len: the number of bytes to read
 * @retlen: the number of bytes actually read
 * @buf: the filled in buffer
 *
 * Returns 0 if read successful, or -ERRNO if an error occurred
 */
static int powernv_flash_read(struct mtd_info *mtd, loff_t from, size_t len,
             size_t *retlen, u_char *buf)
{
        return powernv_flash_async_op(mtd, FLASH_OP_READ, from,
                        len, retlen, buf);
}

/**
 * powernv_flash_write
 * @mtd: the device
 * @to: the offset to write to
 * @len: the number of bytes to write
 * @retlen: the number of bytes actually written
 * @buf: the buffer to get bytes from
 *
 * Returns 0 if write successful, -ERRNO if error occurred
 */
static int powernv_flash_write(struct mtd_info *mtd, loff_t to, size_t len,
                     size_t *retlen, const u_char *buf)
{
        return powernv_flash_async_op(mtd, FLASH_OP_WRITE, to,
                        len, retlen, (u_char *)buf);
}

/**
 * powernv_flash_erase
 * @mtd: the device
 * @erase: the erase info
 * Returns 0 if erase successful or -ERRNO if an error occurred
 */
static int powernv_flash_erase(struct mtd_info *mtd, struct erase_info *erase)
{
        int rc;

        rc =  powernv_flash_async_op(mtd, FLASH_OP_ERASE, erase->addr,
                        erase->len, NULL, NULL);
        if (rc)
                erase->fail_addr = erase->addr;

        return rc;
}

/**
 * powernv_flash_set_driver_info - Fill the mtd_info structure and docg3
 * @dev: The device structure
 * @mtd: The structure to fill
 */
static int powernv_flash_set_driver_info(struct device *dev,
                struct mtd_info *mtd)
{
        u64 size;
        u32 erase_size;
        int rc;

        rc = of_property_read_u32(dev->of_node, "ibm,flash-block-size",
                        &erase_size);
        if (rc) {
                dev_err(dev, "couldn't get resource block size information\n");
                return rc;
        }

        rc = of_property_read_u64(dev->of_node, "reg", &size);
        if (rc) {
                dev_err(dev, "couldn't get resource size information\n");
                return rc;
        }

        /*
         * Going to have to check what details I need to set and how to
         * get them
         */
        mtd->name = devm_kasprintf(dev, GFP_KERNEL, "%pOFP", dev->of_node);
        if (!mtd->name)
                return -ENOMEM;

        mtd->type = MTD_NORFLASH;
        mtd->flags = MTD_WRITEABLE;
        mtd->size = size;
        mtd->erasesize = erase_size;
        mtd->writebufsize = mtd->writesize = 1;
        mtd->owner = THIS_MODULE;
        mtd->_erase = powernv_flash_erase;
        mtd->_read = powernv_flash_read;
        mtd->_write = powernv_flash_write;
        mtd->dev.parent = dev;
        mtd_set_of_node(mtd, dev->of_node);
        return 0;
}

/**
 * powernv_flash_probe
 * @pdev: platform device
 *
 * Returns 0 on success, -ENOMEM, -ENXIO on error
 */
static int powernv_flash_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct powernv_flash *data;
        int ret;

        data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        data->mtd.priv = data;

        ret = of_property_read_u32(dev->of_node, "ibm,opal-id", &(data->id));
        if (ret) {
                dev_err(dev, "no device property 'ibm,opal-id'\n");
                return ret;
        }

        ret = powernv_flash_set_driver_info(dev, &data->mtd);
        if (ret)
                return ret;

        dev_set_drvdata(dev, data);

        /*
         * The current flash that skiboot exposes is one contiguous flash chip
         * with an ffs partition at the start, it should prove easier for users
         * to deal with partitions or not as they see fit
         */
        return mtd_device_register(&data->mtd, NULL, 0);
}

/**
 * op_release - Release the driver
 * @pdev: the platform device
 *
 * Returns 0
 */
static void powernv_flash_release(struct platform_device *pdev)
{
        struct powernv_flash *data = dev_get_drvdata(&(pdev->dev));

        /* All resources should be freed automatically */
        WARN_ON(mtd_device_unregister(&data->mtd));
}

static const struct of_device_id powernv_flash_match[] = {
        { .compatible = "ibm,opal-flash" },
        {}
};

static struct platform_driver powernv_flash_driver = {
        .driver         = {
                .name           = "powernv_flash",
                .of_match_table = powernv_flash_match,
        },
        .remove         = powernv_flash_release,
        .probe          = powernv_flash_probe,
};

module_platform_driver(powernv_flash_driver);

MODULE_DEVICE_TABLE(of, powernv_flash_match);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Cyril Bur <cyril.bur@au1.ibm.com>");
MODULE_DESCRIPTION("MTD abstraction for OPAL flash");