// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * ee1004 - driver for DDR4 SPD EEPROMs
 *
 * Copyright (C) 2017-2019 Jean Delvare
 *
 * Based on the at24 driver:
 * Copyright (C) 2005-2007 David Brownell
 * Copyright (C) 2008 Wolfram Sang, Pengutronix
 */

#include <linux/mfd/qnap-mcu.h>
#include <linux/module.h>
#include <linux/nvmem-provider.h>
#include <linux/platform_device.h>
#include <linux/slab.h>

/* Determined by trial and error until read anomalies appeared */
#define QNAP_MCU_EEPROM_SIZE            256
#define QNAP_MCU_EEPROM_BLOCK_SIZE      32

static int qnap_mcu_eeprom_read_block(struct qnap_mcu *mcu, unsigned int offset,
                                      void *val, size_t bytes)
{
        const u8 cmd[] = { 0xf7, 0xa1, offset, bytes };
        u8 *reply;
        int ret = 0;

        reply = kzalloc(bytes + sizeof(cmd), GFP_KERNEL);
        if (!reply)
                return -ENOMEM;

        ret = qnap_mcu_exec(mcu, cmd, sizeof(cmd), reply, bytes + sizeof(cmd));
        if (ret)
                goto out;

        /* First bytes must mirror the sent command */
        if (memcmp(cmd, reply, sizeof(cmd))) {
                ret = -EIO;
                goto out;
        }

        memcpy(val, reply + sizeof(cmd), bytes);

out:
        kfree(reply);
        return ret;
}

static int qnap_mcu_eeprom_read(void *priv, unsigned int offset, void *val, size_t bytes)
{
        struct qnap_mcu *mcu = priv;
        int pos = 0, ret;
        u8 *buf = val;

        if (unlikely(!bytes))
                return 0;

        while (bytes > 0) {
                size_t to_read = (bytes > QNAP_MCU_EEPROM_BLOCK_SIZE) ?
                                                QNAP_MCU_EEPROM_BLOCK_SIZE : bytes;

                ret = qnap_mcu_eeprom_read_block(mcu, offset + pos, &buf[pos], to_read);
                if (ret < 0)
                        return ret;

                pos += to_read;
                bytes -= to_read;
        }

        return 0;
}

static int qnap_mcu_eeprom_probe(struct platform_device *pdev)
{
        struct qnap_mcu *mcu = dev_get_drvdata(pdev->dev.parent);
        struct nvmem_config nvcfg = {};
        struct nvmem_device *ndev;

        nvcfg.dev = &pdev->dev;
        nvcfg.of_node = pdev->dev.parent->of_node;
        nvcfg.name = dev_name(&pdev->dev);
        nvcfg.id = NVMEM_DEVID_NONE;
        nvcfg.owner = THIS_MODULE;
        nvcfg.type = NVMEM_TYPE_EEPROM;
        nvcfg.read_only = true;
        nvcfg.root_only = false;
        nvcfg.reg_read = qnap_mcu_eeprom_read;
        nvcfg.size = QNAP_MCU_EEPROM_SIZE,
        nvcfg.word_size = 1,
        nvcfg.stride = 1,
        nvcfg.priv = mcu,

        ndev = devm_nvmem_register(&pdev->dev, &nvcfg);
        if (IS_ERR(ndev))
                return PTR_ERR(ndev);

        return 0;
}

static struct platform_driver qnap_mcu_eeprom_driver = {
        .probe = qnap_mcu_eeprom_probe,
        .driver = {
                .name = "qnap-mcu-eeprom",
        },
};
module_platform_driver(qnap_mcu_eeprom_driver);

MODULE_AUTHOR("Heiko Stuebner <heiko@sntech.de>");
MODULE_DESCRIPTION("QNAP MCU EEPROM driver");
MODULE_LICENSE("GPL");