// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   * Freescale MXS On-Chip OTP driver
   *
   * Copyright (C) 2015 Stefan Wahren <stefan.wahren@i2se.com>
   *
   * Based on the driver from Huang Shijie and Christoph G. Baumann

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

  #include <linux/slab.h>
  #include <linux/stmp_device.h>
  
  /* OCOTP registers and bits */
  
  #define BM_OCOTP_CTRL_RD_BANK_OPEN	BIT(12)
  #define BM_OCOTP_CTRL_ERROR		BIT(9)
  #define BM_OCOTP_CTRL_BUSY		BIT(8)
  
  #define OCOTP_TIMEOUT		10000
  #define OCOTP_DATA_OFFSET	0x20
  
  struct mxs_ocotp {
  	struct clk *clk;
  	void __iomem *base;
  	struct nvmem_device *nvmem;
  };
  
  static int mxs_ocotp_wait(struct mxs_ocotp *otp)
  {
  	int timeout = OCOTP_TIMEOUT;
  	unsigned int status = 0;
  
  	while (timeout--) {
  		status = readl(otp->base);
  
  		if (!(status & (BM_OCOTP_CTRL_BUSY | BM_OCOTP_CTRL_ERROR)))
  			break;
  
  		cpu_relax();
  	}
  
  	if (status & BM_OCOTP_CTRL_BUSY)
  		return -EBUSY;
  	else if (status & BM_OCOTP_CTRL_ERROR)
  		return -EIO;
  
  	return 0;
  }

  static int mxs_ocotp_read(void *context, unsigned int offset,
  			  void *val, size_t bytes)

  {
  	struct mxs_ocotp *otp = context;

  	u32 *buf = val;
  	int ret;
  
  	ret = clk_enable(otp->clk);
  	if (ret)
  		return ret;
  
  	writel(BM_OCOTP_CTRL_ERROR, otp->base + STMP_OFFSET_REG_CLR);
  
  	ret = mxs_ocotp_wait(otp);
  	if (ret)
  		goto disable_clk;
  
  	/* open OCOTP banks for read */
  	writel(BM_OCOTP_CTRL_RD_BANK_OPEN, otp->base + STMP_OFFSET_REG_SET);
  
  	/* approximately wait 33 hclk cycles */
  	udelay(1);
  
  	ret = mxs_ocotp_wait(otp);
  	if (ret)
  		goto close_banks;

  	while (bytes) {

  		if ((offset < OCOTP_DATA_OFFSET) || (offset % 16)) {
  			/* fill up non-data register */

  			*buf++ = 0;

  		} else {

  			*buf++ = readl(otp->base + offset);

  		}

  		bytes -= 4;
  		offset += 4;

  	}
  
  close_banks:
  	/* close banks for power saving */
  	writel(BM_OCOTP_CTRL_RD_BANK_OPEN, otp->base + STMP_OFFSET_REG_CLR);
  
  disable_clk:
  	clk_disable(otp->clk);
  
  	return ret;
  }

  static struct nvmem_config ocotp_config = {
  	.name = "mxs-ocotp",

  	.stride = 16,
  	.word_size = 4,

  	.reg_read = mxs_ocotp_read,

  };

  struct mxs_data {
  	int size;

  };

  static const struct mxs_data imx23_data = {
  	.size = 0x220,

  };

  static const struct mxs_data imx28_data = {
  	.size = 0x2a0,

  };
  
  static const struct of_device_id mxs_ocotp_match[] = {

  	{ .compatible = "fsl,imx23-ocotp", .data = &imx23_data },
  	{ .compatible = "fsl,imx28-ocotp", .data = &imx28_data },

  	{ /* sentinel */},
  };
  MODULE_DEVICE_TABLE(of, mxs_ocotp_match);

  static void mxs_ocotp_action(void *data)
  {
  	clk_unprepare(data);
  }

  static int mxs_ocotp_probe(struct platform_device *pdev)
  {
  	struct device *dev = &pdev->dev;

  	const struct mxs_data *data;

  	struct mxs_ocotp *otp;

  	const struct of_device_id *match;

  	int ret;
  
  	match = of_match_device(dev->driver->of_match_table, dev);
  	if (!match || !match->data)
  		return -EINVAL;
  
  	otp = devm_kzalloc(dev, sizeof(*otp), GFP_KERNEL);
  	if (!otp)
  		return -ENOMEM;

  	otp->base = devm_platform_ioremap_resource(pdev, 0);

  	if (IS_ERR(otp->base))
  		return PTR_ERR(otp->base);
  
  	otp->clk = devm_clk_get(&pdev->dev, NULL);
  	if (IS_ERR(otp->clk))
  		return PTR_ERR(otp->clk);
  
  	ret = clk_prepare(otp->clk);
  	if (ret < 0) {
  		dev_err(dev, "failed to prepare clk: %d
  ", ret);
  		return ret;
  	}

  	ret = devm_add_action_or_reset(&pdev->dev, mxs_ocotp_action, otp->clk);
  	if (ret)
  		return ret;

  	data = match->data;

  	ocotp_config.size = data->size;
  	ocotp_config.priv = otp;

  	ocotp_config.dev = dev;

  	otp->nvmem = devm_nvmem_register(dev, &ocotp_config);

  	if (IS_ERR(otp->nvmem))
  		return PTR_ERR(otp->nvmem);

  
  	platform_set_drvdata(pdev, otp);
  
  	return 0;

  }
  
  static struct platform_driver mxs_ocotp_driver = {
  	.probe = mxs_ocotp_probe,

  	.driver = {
  		.name = "mxs-ocotp",
  		.of_match_table = mxs_ocotp_match,
  	},
  };
  
  module_platform_driver(mxs_ocotp_driver);

  MODULE_AUTHOR("Stefan Wahren <wahrenst@gmx.net");

  MODULE_DESCRIPTION("driver for OCOTP in i.MX23/i.MX28");
  MODULE_LICENSE("GPL v2");