/*
 * i.MX6 OCOTP fusebox driver
 *
 * Copyright (c) 2015 Pengutronix, Philipp Zabel <p.zabel@pengutronix.de>
 *
 * Based on the barebox ocotp driver,
 * Copyright (c) 2010 Baruch Siach <baruch@tkos.co.il>,
 *      Orex Computed Radiography
 *
 * Write support based on the fsl_otp driver,
 * Copyright (C) 2010-2013 Freescale Semiconductor, Inc
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation.
 *
 * http://www.opensource.org/licenses/gpl-license.html
 * http://www.gnu.org/copyleft/gpl.html
 */

#include <linux/clk.h>
#include <linux/device.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/nvmem-provider.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/delay.h>

#define IMX_OCOTP_OFFSET_B0W0           0x400 /* Offset from base address of the
                                               * OTP Bank0 Word0
                                               */
#define IMX_OCOTP_OFFSET_PER_WORD       0x10  /* Offset between the start addr
                                               * of two consecutive OTP words.
                                               */

#define IMX_OCOTP_ADDR_CTRL             0x0000
#define IMX_OCOTP_ADDR_CTRL_SET         0x0004
#define IMX_OCOTP_ADDR_CTRL_CLR         0x0008
#define IMX_OCOTP_ADDR_TIMING           0x0010
#define IMX_OCOTP_ADDR_DATA0            0x0020
#define IMX_OCOTP_ADDR_DATA1            0x0030
#define IMX_OCOTP_ADDR_DATA2            0x0040
#define IMX_OCOTP_ADDR_DATA3            0x0050

#define IMX_OCOTP_BM_CTRL_ADDR          0x0000007F
#define IMX_OCOTP_BM_CTRL_BUSY          0x00000100
#define IMX_OCOTP_BM_CTRL_ERROR         0x00000200
#define IMX_OCOTP_BM_CTRL_REL_SHADOWS   0x00000400

#define DEF_RELAX                       20      /* > 16.5ns */
#define DEF_FSOURCE                     1001    /* > 1000 ns */
#define DEF_STROBE_PROG                 10000   /* IPG clocks */
#define IMX_OCOTP_WR_UNLOCK             0x3E770000
#define IMX_OCOTP_READ_LOCKED_VAL       0xBADABADA

static DEFINE_MUTEX(ocotp_mutex);

struct ocotp_priv {
        struct device *dev;
        struct clk *clk;
        void __iomem *base;
        const struct ocotp_params *params;
        struct nvmem_config *config;
};

struct ocotp_params {
        unsigned int nregs;
        unsigned int bank_address_words;
        void (*set_timing)(struct ocotp_priv *priv);
};

static int imx_ocotp_wait_for_busy(void __iomem *base, u32 flags)
{
        int count;
        u32 c, mask;

        mask = IMX_OCOTP_BM_CTRL_BUSY | IMX_OCOTP_BM_CTRL_ERROR | flags;

        for (count = 10000; count >= 0; count--) {
                c = readl(base + IMX_OCOTP_ADDR_CTRL);
                if (!(c & mask))
                        break;
                cpu_relax();
        }

        if (count < 0) {
                /* HW_OCOTP_CTRL[ERROR] will be set under the following
                 * conditions:
                 * - A write is performed to a shadow register during a shadow
                 *   reload (essentially, while HW_OCOTP_CTRL[RELOAD_SHADOWS] is
                 *   set. In addition, the contents of the shadow register shall
                 *   not be updated.
                 * - A write is performed to a shadow register which has been
                 *   locked.
                 * - A read is performed to from a shadow register which has
                 *   been read locked.
                 * - A program is performed to a fuse word which has been locked
                 * - A read is performed to from a fuse word which has been read
                 *   locked.
                 */
                if (c & IMX_OCOTP_BM_CTRL_ERROR)
                        return -EPERM;
                return -ETIMEDOUT;
        }

        return 0;
}

static void imx_ocotp_clr_err_if_set(void __iomem *base)
{
        u32 c;

        c = readl(base + IMX_OCOTP_ADDR_CTRL);
        if (!(c & IMX_OCOTP_BM_CTRL_ERROR))
                return;

        writel(IMX_OCOTP_BM_CTRL_ERROR, base + IMX_OCOTP_ADDR_CTRL_CLR);
}

static int imx_ocotp_read(void *context, unsigned int offset,
                          void *val, size_t bytes)
{
        struct ocotp_priv *priv = context;
        unsigned int count;
        u32 *buf = val;
        int i, ret;
        u32 index;

        index = offset >> 2;
        count = bytes >> 2;

        if (count > (priv->params->nregs - index))
                count = priv->params->nregs - index;

        mutex_lock(&ocotp_mutex);

        ret = clk_prepare_enable(priv->clk);
        if (ret < 0) {
                mutex_unlock(&ocotp_mutex);
                dev_err(priv->dev, "failed to prepare/enable ocotp clk\n");
                return ret;
        }

        ret = imx_ocotp_wait_for_busy(priv->base, 0);
        if (ret < 0) {
                dev_err(priv->dev, "timeout during read setup\n");
                goto read_end;
        }

        for (i = index; i < (index + count); i++) {
                *buf++ = readl(priv->base + IMX_OCOTP_OFFSET_B0W0 +
                               i * IMX_OCOTP_OFFSET_PER_WORD);

                /* 47.3.1.2
                 * For "read locked" registers 0xBADABADA will be returned and
                 * HW_OCOTP_CTRL[ERROR] will be set. It must be cleared by
                 * software before any new write, read or reload access can be
                 * issued
                 */
                if (*(buf - 1) == IMX_OCOTP_READ_LOCKED_VAL)
                        imx_ocotp_clr_err_if_set(priv->base);
        }
        ret = 0;

read_end:
        clk_disable_unprepare(priv->clk);
        mutex_unlock(&ocotp_mutex);
        return ret;
}

static void imx_ocotp_set_imx6_timing(struct ocotp_priv *priv)
{
        unsigned long clk_rate = 0;
        unsigned long strobe_read, relax, strobe_prog;
        u32 timing = 0;

        /* 47.3.1.3.1
         * Program HW_OCOTP_TIMING[STROBE_PROG] and HW_OCOTP_TIMING[RELAX]
         * fields with timing values to match the current frequency of the
         * ipg_clk. OTP writes will work at maximum bus frequencies as long
         * as the HW_OCOTP_TIMING parameters are set correctly.
         */
        clk_rate = clk_get_rate(priv->clk);

        relax = clk_rate / (1000000000 / DEF_RELAX) - 1;
        strobe_prog = clk_rate / (1000000000 / 10000) + 2 * (DEF_RELAX + 1) - 1;
        strobe_read = clk_rate / (1000000000 / 40) + 2 * (DEF_RELAX + 1) - 1;

        timing = strobe_prog & 0x00000FFF;
        timing |= (relax       << 12) & 0x0000F000;
        timing |= (strobe_read << 16) & 0x003F0000;

        writel(timing, priv->base + IMX_OCOTP_ADDR_TIMING);
}

static void imx_ocotp_set_imx7_timing(struct ocotp_priv *priv)
{
        unsigned long clk_rate = 0;
        u64 fsource, strobe_prog;
        u32 timing = 0;

        /* i.MX 7Solo Applications Processor Reference Manual, Rev. 0.1
         * 6.4.3.3
         */
        clk_rate = clk_get_rate(priv->clk);
        fsource = DIV_ROUND_UP_ULL((u64)clk_rate * DEF_FSOURCE,
                                   NSEC_PER_SEC) + 1;
        strobe_prog = DIV_ROUND_CLOSEST_ULL((u64)clk_rate * DEF_STROBE_PROG,
                                            NSEC_PER_SEC) + 1;

        timing = strobe_prog & 0x00000FFF;
        timing |= (fsource << 12) & 0x000FF000;

        writel(timing, priv->base + IMX_OCOTP_ADDR_TIMING);
}

static int imx_ocotp_write(void *context, unsigned int offset, void *val,
                           size_t bytes)
{
        struct ocotp_priv *priv = context;
        u32 *buf = val;
        int ret;

        u32 ctrl;
        u8 waddr;
        u8 word = 0;

        /* allow only writing one complete OTP word at a time */
        if ((bytes != priv->config->word_size) ||
            (offset % priv->config->word_size))
                return -EINVAL;

        mutex_lock(&ocotp_mutex);

        ret = clk_prepare_enable(priv->clk);
        if (ret < 0) {
                mutex_unlock(&ocotp_mutex);
                dev_err(priv->dev, "failed to prepare/enable ocotp clk\n");
                return ret;
        }

        /* Setup the write timing values */
        priv->params->set_timing(priv);

        /* 47.3.1.3.2
         * Check that HW_OCOTP_CTRL[BUSY] and HW_OCOTP_CTRL[ERROR] are clear.
         * Overlapped accesses are not supported by the controller. Any pending
         * write or reload must be completed before a write access can be
         * requested.
         */
        ret = imx_ocotp_wait_for_busy(priv->base, 0);
        if (ret < 0) {
                dev_err(priv->dev, "timeout during timing setup\n");
                goto write_end;
        }

        /* 47.3.1.3.3
         * Write the requested address to HW_OCOTP_CTRL[ADDR] and program the
         * unlock code into HW_OCOTP_CTRL[WR_UNLOCK]. This must be programmed
         * for each write access. The lock code is documented in the register
         * description. Both the unlock code and address can be written in the
         * same operation.
         */
        if (priv->params->bank_address_words != 0) {
                /*
                 * In banked/i.MX7 mode the OTP register bank goes into waddr
                 * see i.MX 7Solo Applications Processor Reference Manual, Rev.
                 * 0.1 section 6.4.3.1
                 */
                offset = offset / priv->config->word_size;
                waddr = offset / priv->params->bank_address_words;
                word  = offset & (priv->params->bank_address_words - 1);
        } else {
                /*
                 * Non-banked i.MX6 mode.
                 * OTP write/read address specifies one of 128 word address
                 * locations
                 */
                waddr = offset / 4;
        }

        ctrl = readl(priv->base + IMX_OCOTP_ADDR_CTRL);
        ctrl &= ~IMX_OCOTP_BM_CTRL_ADDR;
        ctrl |= waddr & IMX_OCOTP_BM_CTRL_ADDR;
        ctrl |= IMX_OCOTP_WR_UNLOCK;

        writel(ctrl, priv->base + IMX_OCOTP_ADDR_CTRL);

        /* 47.3.1.3.4
         * Write the data to the HW_OCOTP_DATA register. This will automatically
         * set HW_OCOTP_CTRL[BUSY] and clear HW_OCOTP_CTRL[WR_UNLOCK]. To
         * protect programming same OTP bit twice, before program OCOTP will
         * automatically read fuse value in OTP and use read value to mask
         * program data. The controller will use masked program data to program
         * a 32-bit word in the OTP per the address in HW_OCOTP_CTRL[ADDR]. Bit
         * fields with 1's will result in that OTP bit being programmed. Bit
         * fields with 0's will be ignored. At the same time that the write is
         * accepted, the controller makes an internal copy of
         * HW_OCOTP_CTRL[ADDR] which cannot be updated until the next write
         * sequence is initiated. This copy guarantees that erroneous writes to
         * HW_OCOTP_CTRL[ADDR] will not affect an active write operation. It
         * should also be noted that during the programming HW_OCOTP_DATA will
         * shift right (with zero fill). This shifting is required to program
         * the OTP serially. During the write operation, HW_OCOTP_DATA cannot be
         * modified.
         * Note: on i.MX7 there are four data fields to write for banked write
         *       with the fuse blowing operation only taking place after data0
         *       has been written. This is why data0 must always be the last
         *       register written.
         */
        if (priv->params->bank_address_words != 0) {
                /* Banked/i.MX7 mode */
                switch (word) {
                case 0:
                        writel(0, priv->base + IMX_OCOTP_ADDR_DATA1);
                        writel(0, priv->base + IMX_OCOTP_ADDR_DATA2);
                        writel(0, priv->base + IMX_OCOTP_ADDR_DATA3);
                        writel(*buf, priv->base + IMX_OCOTP_ADDR_DATA0);
                        break;
                case 1:
                        writel(*buf, priv->base + IMX_OCOTP_ADDR_DATA1);
                        writel(0, priv->base + IMX_OCOTP_ADDR_DATA2);
                        writel(0, priv->base + IMX_OCOTP_ADDR_DATA3);
                        writel(0, priv->base + IMX_OCOTP_ADDR_DATA0);
                        break;
                case 2:
                        writel(0, priv->base + IMX_OCOTP_ADDR_DATA1);
                        writel(*buf, priv->base + IMX_OCOTP_ADDR_DATA2);
                        writel(0, priv->base + IMX_OCOTP_ADDR_DATA3);
                        writel(0, priv->base + IMX_OCOTP_ADDR_DATA0);
                        break;
                case 3:
                        writel(0, priv->base + IMX_OCOTP_ADDR_DATA1);
                        writel(0, priv->base + IMX_OCOTP_ADDR_DATA2);
                        writel(*buf, priv->base + IMX_OCOTP_ADDR_DATA3);
                        writel(0, priv->base + IMX_OCOTP_ADDR_DATA0);
                        break;
                }
        } else {
                /* Non-banked i.MX6 mode */
                writel(*buf, priv->base + IMX_OCOTP_ADDR_DATA0);
        }

        /* 47.4.1.4.5
         * Once complete, the controller will clear BUSY. A write request to a
         * protected or locked region will result in no OTP access and no
         * setting of HW_OCOTP_CTRL[BUSY]. In addition HW_OCOTP_CTRL[ERROR] will
         * be set. It must be cleared by software before any new write access
         * can be issued.
         */
        ret = imx_ocotp_wait_for_busy(priv->base, 0);
        if (ret < 0) {
                if (ret == -EPERM) {
                        dev_err(priv->dev, "failed write to locked region");
                        imx_ocotp_clr_err_if_set(priv->base);
                } else {
                        dev_err(priv->dev, "timeout during data write\n");
                }
                goto write_end;
        }

        /* 47.3.1.4
         * Write Postamble: Due to internal electrical characteristics of the
         * OTP during writes, all OTP operations following a write must be
         * separated by 2 us after the clearing of HW_OCOTP_CTRL_BUSY following
         * the write.
         */
        udelay(2);

        /* reload all shadow registers */
        writel(IMX_OCOTP_BM_CTRL_REL_SHADOWS,
               priv->base + IMX_OCOTP_ADDR_CTRL_SET);
        ret = imx_ocotp_wait_for_busy(priv->base,
                                      IMX_OCOTP_BM_CTRL_REL_SHADOWS);
        if (ret < 0) {
                dev_err(priv->dev, "timeout during shadow register reload\n");
                goto write_end;
        }

write_end:
        clk_disable_unprepare(priv->clk);
        mutex_unlock(&ocotp_mutex);
        if (ret < 0)
                return ret;
        return bytes;
}

static struct nvmem_config imx_ocotp_nvmem_config = {
        .name = "imx-ocotp",
        .read_only = false,
        .word_size = 4,
        .stride = 4,
        .reg_read = imx_ocotp_read,
        .reg_write = imx_ocotp_write,
};

static const struct ocotp_params imx6q_params = {
        .nregs = 128,
        .bank_address_words = 0,
        .set_timing = imx_ocotp_set_imx6_timing,
};

static const struct ocotp_params imx6sl_params = {
        .nregs = 64,
        .bank_address_words = 0,
        .set_timing = imx_ocotp_set_imx6_timing,
};

static const struct ocotp_params imx6sx_params = {
        .nregs = 128,
        .bank_address_words = 0,
        .set_timing = imx_ocotp_set_imx6_timing,
};

static const struct ocotp_params imx6ul_params = {
        .nregs = 128,
        .bank_address_words = 0,
        .set_timing = imx_ocotp_set_imx6_timing,
};

static const struct ocotp_params imx7d_params = {
        .nregs = 64,
        .bank_address_words = 4,
        .set_timing = imx_ocotp_set_imx7_timing,
};

static const struct of_device_id imx_ocotp_dt_ids[] = {
        { .compatible = "fsl,imx6q-ocotp",  .data = &imx6q_params },
        { .compatible = "fsl,imx6sl-ocotp", .data = &imx6sl_params },
        { .compatible = "fsl,imx6sx-ocotp", .data = &imx6sx_params },
        { .compatible = "fsl,imx6ul-ocotp", .data = &imx6ul_params },
        { .compatible = "fsl,imx7d-ocotp",  .data = &imx7d_params },
        { },
};
MODULE_DEVICE_TABLE(of, imx_ocotp_dt_ids);

static int imx_ocotp_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct resource *res;
        struct ocotp_priv *priv;
        struct nvmem_device *nvmem;

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

        priv->dev = dev;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        priv->base = devm_ioremap_resource(dev, res);
        if (IS_ERR(priv->base))
                return PTR_ERR(priv->base);

        priv->clk = devm_clk_get(dev, NULL);
        if (IS_ERR(priv->clk))
                return PTR_ERR(priv->clk);

        priv->params = of_device_get_match_data(&pdev->dev);
        imx_ocotp_nvmem_config.size = 4 * priv->params->nregs;
        imx_ocotp_nvmem_config.dev = dev;
        imx_ocotp_nvmem_config.priv = priv;
        priv->config = &imx_ocotp_nvmem_config;
        nvmem = devm_nvmem_register(dev, &imx_ocotp_nvmem_config);


        return PTR_ERR_OR_ZERO(nvmem);
}

static struct platform_driver imx_ocotp_driver = {
        .probe  = imx_ocotp_probe,
        .driver = {
                .name   = "imx_ocotp",
                .of_match_table = imx_ocotp_dt_ids,
        },
};
module_platform_driver(imx_ocotp_driver);

MODULE_AUTHOR("Philipp Zabel <p.zabel@pengutronix.de>");
MODULE_DESCRIPTION("i.MX6/i.MX7 OCOTP fuse box driver");
MODULE_LICENSE("GPL v2");