// SPDX-License-Identifier: GPL-2.0-only
/*
 * sfr.c - driver for special function registers
 *
 * Copyright (C) 2019 Bootlin.
 *
 */
#include <linux/mfd/syscon.h>
#include <linux/module.h>
#include <linux/nvmem-provider.h>
#include <linux/random.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/regmap.h>

#define SFR_SN0         0x4c
#define SFR_SN_SIZE     8

struct atmel_sfr_priv {
        struct regmap                   *regmap;
};

static int atmel_sfr_read(void *context, unsigned int offset,
                          void *buf, size_t bytes)
{
        struct atmel_sfr_priv *priv = context;

        return regmap_bulk_read(priv->regmap, SFR_SN0 + offset,
                                buf, bytes / 4);
}

static struct nvmem_config atmel_sfr_nvmem_config = {
        .name = "atmel-sfr",
        .read_only = true,
        .word_size = 4,
        .stride = 4,
        .size = SFR_SN_SIZE,
        .reg_read = atmel_sfr_read,
};

static int atmel_sfr_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct device_node *np = dev->of_node;
        struct nvmem_device *nvmem;
        struct atmel_sfr_priv *priv;
        u8 sn[SFR_SN_SIZE];
        int ret;

        priv = devm_kmalloc(dev, sizeof(*priv), GFP_KERNEL);
        if (!priv)
                return -ENOMEM;

        priv->regmap = syscon_node_to_regmap(np);
        if (IS_ERR(priv->regmap)) {
                dev_err(dev, "cannot get parent's regmap\n");
                return PTR_ERR(priv->regmap);
        }

        atmel_sfr_nvmem_config.dev = dev;
        atmel_sfr_nvmem_config.priv = priv;

        nvmem = devm_nvmem_register(dev, &atmel_sfr_nvmem_config);
        if (IS_ERR(nvmem)) {
                dev_err(dev, "error registering nvmem config\n");
                return PTR_ERR(nvmem);
        }

        ret = atmel_sfr_read(priv, 0, sn, SFR_SN_SIZE);
        if (ret == 0)
                add_device_randomness(sn, SFR_SN_SIZE);

        return ret;
}

static const struct of_device_id atmel_sfr_dt_ids[] = {
        {
                .compatible = "atmel,sama5d2-sfr",
        }, {
                .compatible = "atmel,sama5d4-sfr",
        }, {
                /* sentinel */
        },
};
MODULE_DEVICE_TABLE(of, atmel_sfr_dt_ids);

static struct platform_driver atmel_sfr_driver = {
        .probe = atmel_sfr_probe,
        .driver = {
                .name = "atmel-sfr",
                .of_match_table = atmel_sfr_dt_ids,
        },
};
module_platform_driver(atmel_sfr_driver);

MODULE_AUTHOR("Kamel Bouhara <kamel.bouhara@bootlin.com>");
MODULE_DESCRIPTION("Atmel SFR SN driver for SAMA5D2/4 SoC family");
MODULE_LICENSE("GPL v2");