// SPDX-License-Identifier: GPL-2.0+
/*
 * Allwinner sunXi SoCs Security ID support.
 *
 * Copyright (c) 2013 Oliver Schinagl <oliver@schinagl.nl>
 * Copyright (C) 2014 Maxime Ripard <maxime.ripard@free-electrons.com>
 */

#include <linux/device.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/nvmem-provider.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/random.h>

/* Registers and special values for doing register-based SID readout on H3 */
#define SUN8I_SID_PRCTL         0x40
#define SUN8I_SID_RDKEY         0x60

#define SUN8I_SID_OFFSET_MASK   0x1FF
#define SUN8I_SID_OFFSET_SHIFT  16
#define SUN8I_SID_OP_LOCK       (0xAC << 8)
#define SUN8I_SID_READ          BIT(1)

struct sunxi_sid_cfg {
        u32     value_offset;
        u32     size;
        bool    need_register_readout;
};

struct sunxi_sid {
        void __iomem            *base;
        u32                     value_offset;
};

static int sunxi_sid_read(void *context, unsigned int offset,
                          void *val, size_t bytes)
{
        struct sunxi_sid *sid = context;
        u32 word;

        /* .stride = 4 so offset is guaranteed to be aligned */
        __ioread32_copy(val, sid->base + sid->value_offset + offset, bytes / 4);

        val += round_down(bytes, 4);
        offset += round_down(bytes, 4);
        bytes = bytes % 4;

        if (!bytes)
                return 0;

        /* Handle any trailing bytes */
        word = readl_relaxed(sid->base + sid->value_offset + offset);
        memcpy(val, &word, bytes);

        return 0;
}

static int sun8i_sid_register_readout(const struct sunxi_sid *sid,
                                      const unsigned int offset,
                                      u32 *out)
{
        u32 reg_val;
        int ret;

        /* Set word, lock access, and set read command */
        reg_val = (offset & SUN8I_SID_OFFSET_MASK)
                  << SUN8I_SID_OFFSET_SHIFT;
        reg_val |= SUN8I_SID_OP_LOCK | SUN8I_SID_READ;
        writel(reg_val, sid->base + SUN8I_SID_PRCTL);

        ret = readl_poll_timeout(sid->base + SUN8I_SID_PRCTL, reg_val,
                                 !(reg_val & SUN8I_SID_READ), 100, 250000);
        if (ret)
                return ret;

        if (out)
                *out = readl(sid->base + SUN8I_SID_RDKEY);

        writel(0, sid->base + SUN8I_SID_PRCTL);

        return 0;
}

/*
 * On Allwinner H3, the value on the 0x200 offset of the SID controller seems
 * to be not reliable at all.
 * Read by the registers instead.
 */
static int sun8i_sid_read_by_reg(void *context, unsigned int offset,
                                 void *val, size_t bytes)
{
        struct sunxi_sid *sid = context;
        u32 word;
        int ret;

        /* .stride = 4 so offset is guaranteed to be aligned */
        while (bytes >= 4) {
                ret = sun8i_sid_register_readout(sid, offset, val);
                if (ret)
                        return ret;

                val += 4;
                offset += 4;
                bytes -= 4;
        }

        if (!bytes)
                return 0;

        /* Handle any trailing bytes */
        ret = sun8i_sid_register_readout(sid, offset, &word);
        if (ret)
                return ret;

        memcpy(val, &word, bytes);

        return 0;
}

static int sunxi_sid_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct nvmem_config *nvmem_cfg;
        struct nvmem_device *nvmem;
        struct sunxi_sid *sid;
        int size;
        char *randomness;
        const struct sunxi_sid_cfg *cfg;

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

        cfg = of_device_get_match_data(dev);
        if (!cfg)
                return -EINVAL;
        sid->value_offset = cfg->value_offset;

        sid->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(sid->base))
                return PTR_ERR(sid->base);

        size = cfg->size;

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

        nvmem_cfg->dev = dev;
        nvmem_cfg->name = "sunxi-sid";
        nvmem_cfg->type = NVMEM_TYPE_OTP;
        nvmem_cfg->add_legacy_fixed_of_cells = true;
        nvmem_cfg->read_only = true;
        nvmem_cfg->size = cfg->size;
        nvmem_cfg->word_size = 1;
        nvmem_cfg->stride = 4;
        nvmem_cfg->priv = sid;
        if (cfg->need_register_readout)
                nvmem_cfg->reg_read = sun8i_sid_read_by_reg;
        else
                nvmem_cfg->reg_read = sunxi_sid_read;

        nvmem = devm_nvmem_register(dev, nvmem_cfg);
        if (IS_ERR(nvmem))
                return PTR_ERR(nvmem);

        randomness = kzalloc(size, GFP_KERNEL);
        if (!randomness)
                return -ENOMEM;

        nvmem_cfg->reg_read(sid, 0, randomness, size);
        add_device_randomness(randomness, size);
        kfree(randomness);

        platform_set_drvdata(pdev, nvmem);

        return 0;
}

static const struct sunxi_sid_cfg sun4i_a10_cfg = {
        .size = 0x10,
};

static const struct sunxi_sid_cfg sun7i_a20_cfg = {
        .size = 0x200,
};

static const struct sunxi_sid_cfg sun8i_h3_cfg = {
        .value_offset = 0x200,
        .size = 0x100,
        .need_register_readout = true,
};

static const struct sunxi_sid_cfg sun50i_a64_cfg = {
        .value_offset = 0x200,
        .size = 0x100,
};

static const struct sunxi_sid_cfg sun50i_h6_cfg = {
        .value_offset = 0x200,
        .size = 0x200,
};

static const struct of_device_id sunxi_sid_of_match[] = {
        { .compatible = "allwinner,sun4i-a10-sid", .data = &sun4i_a10_cfg },
        { .compatible = "allwinner,sun7i-a20-sid", .data = &sun7i_a20_cfg },
        { .compatible = "allwinner,sun8i-a83t-sid", .data = &sun50i_a64_cfg },
        { .compatible = "allwinner,sun8i-h3-sid", .data = &sun8i_h3_cfg },
        { .compatible = "allwinner,sun20i-d1-sid", .data = &sun50i_a64_cfg },
        { .compatible = "allwinner,sun50i-a64-sid", .data = &sun50i_a64_cfg },
        { .compatible = "allwinner,sun50i-h5-sid", .data = &sun50i_a64_cfg },
        { .compatible = "allwinner,sun50i-h6-sid", .data = &sun50i_h6_cfg },
        {/* sentinel */},
};
MODULE_DEVICE_TABLE(of, sunxi_sid_of_match);

static struct platform_driver sunxi_sid_driver = {
        .probe = sunxi_sid_probe,
        .driver = {
                .name = "eeprom-sunxi-sid",
                .of_match_table = sunxi_sid_of_match,
        },
};
module_platform_driver(sunxi_sid_driver);

MODULE_AUTHOR("Oliver Schinagl <oliver@schinagl.nl>");
MODULE_DESCRIPTION("Allwinner sunxi security id driver");
MODULE_LICENSE("GPL");