// SPDX-License-Identifier: GPL-2.0+

  /*
   * ST's LPC Watchdog
   *
   * Copyright (C) 2014 STMicroelectronics -- All Rights Reserved
   *
   * Author: David Paris <david.paris@st.com> for STMicroelectronics
   *         Lee Jones <lee.jones@linaro.org> for STMicroelectronics

   */
  
  #include <linux/clk.h>
  #include <linux/init.h>
  #include <linux/io.h>
  #include <linux/kernel.h>
  #include <linux/mfd/syscon.h>
  #include <linux/module.h>
  #include <linux/of.h>
  #include <linux/of_platform.h>
  #include <linux/platform_device.h>
  #include <linux/regmap.h>
  #include <linux/watchdog.h>
  
  #include <dt-bindings/mfd/st-lpc.h>
  
  /* Low Power Alarm */
  #define LPC_LPA_LSB_OFF			0x410
  #define LPC_LPA_START_OFF		0x418
  
  /* LPC as WDT */
  #define LPC_WDT_OFF			0x510
  
  static struct watchdog_device st_wdog_dev;
  
  struct st_wdog_syscfg {
  	unsigned int reset_type_reg;
  	unsigned int reset_type_mask;
  	unsigned int enable_reg;
  	unsigned int enable_mask;
  };
  
  struct st_wdog {
  	void __iomem *base;
  	struct device *dev;
  	struct regmap *regmap;
  	struct st_wdog_syscfg *syscfg;
  	struct clk *clk;
  	unsigned long clkrate;
  	bool warm_reset;
  };

  static struct st_wdog_syscfg stih407_syscfg = {
  	.enable_reg		= 0x204,
  	.enable_mask		= BIT(19),
  };
  
  static const struct of_device_id st_wdog_match[] = {
  	{
  		.compatible = "st,stih407-lpc",
  		.data = &stih407_syscfg,
  	},

  	{},
  };
  MODULE_DEVICE_TABLE(of, st_wdog_match);
  
  static void st_wdog_setup(struct st_wdog *st_wdog, bool enable)
  {
  	/* Type of watchdog reset - 0: Cold 1: Warm */
  	if (st_wdog->syscfg->reset_type_reg)
  		regmap_update_bits(st_wdog->regmap,
  				   st_wdog->syscfg->reset_type_reg,
  				   st_wdog->syscfg->reset_type_mask,
  				   st_wdog->warm_reset);
  
  	/* Mask/unmask watchdog reset */
  	regmap_update_bits(st_wdog->regmap,
  			   st_wdog->syscfg->enable_reg,
  			   st_wdog->syscfg->enable_mask,
  			   enable ? 0 : st_wdog->syscfg->enable_mask);
  }
  
  static void st_wdog_load_timer(struct st_wdog *st_wdog, unsigned int timeout)
  {
  	unsigned long clkrate = st_wdog->clkrate;
  
  	writel_relaxed(timeout * clkrate, st_wdog->base + LPC_LPA_LSB_OFF);
  	writel_relaxed(1, st_wdog->base + LPC_LPA_START_OFF);
  }
  
  static int st_wdog_start(struct watchdog_device *wdd)
  {
  	struct st_wdog *st_wdog = watchdog_get_drvdata(wdd);
  
  	writel_relaxed(1, st_wdog->base + LPC_WDT_OFF);
  
  	return 0;
  }
  
  static int st_wdog_stop(struct watchdog_device *wdd)
  {
  	struct st_wdog *st_wdog = watchdog_get_drvdata(wdd);
  
  	writel_relaxed(0, st_wdog->base + LPC_WDT_OFF);
  
  	return 0;
  }
  
  static int st_wdog_set_timeout(struct watchdog_device *wdd,
  			       unsigned int timeout)
  {
  	struct st_wdog *st_wdog = watchdog_get_drvdata(wdd);
  
  	wdd->timeout = timeout;
  	st_wdog_load_timer(st_wdog, timeout);
  
  	return 0;
  }
  
  static int st_wdog_keepalive(struct watchdog_device *wdd)
  {
  	struct st_wdog *st_wdog = watchdog_get_drvdata(wdd);
  
  	st_wdog_load_timer(st_wdog, wdd->timeout);
  
  	return 0;
  }
  
  static const struct watchdog_info st_wdog_info = {
  	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
  	.identity = "ST LPC WDT",
  };
  
  static const struct watchdog_ops st_wdog_ops = {
  	.owner		= THIS_MODULE,
  	.start		= st_wdog_start,
  	.stop		= st_wdog_stop,
  	.ping		= st_wdog_keepalive,
  	.set_timeout	= st_wdog_set_timeout,
  };
  
  static struct watchdog_device st_wdog_dev = {
  	.info		= &st_wdog_info,
  	.ops		= &st_wdog_ops,
  };

  static void st_clk_disable_unprepare(void *data)
  {
  	clk_disable_unprepare(data);
  }

  static int st_wdog_probe(struct platform_device *pdev)
  {

  	struct device *dev = &pdev->dev;

  	const struct of_device_id *match;

  	struct device_node *np = dev->of_node;

  	struct st_wdog *st_wdog;
  	struct regmap *regmap;

  	struct clk *clk;
  	void __iomem *base;
  	uint32_t mode;
  	int ret;
  
  	ret = of_property_read_u32(np, "st,lpc-mode", &mode);
  	if (ret) {

  		dev_err(dev, "An LPC mode must be provided
  ");

  		return -EINVAL;
  	}

  	/* LPC can either run as a Clocksource or in RTC or WDT mode */

  	if (mode != ST_LPC_MODE_WDT)
  		return -ENODEV;

  	st_wdog = devm_kzalloc(dev, sizeof(*st_wdog), GFP_KERNEL);

  	if (!st_wdog)
  		return -ENOMEM;

  	match = of_match_device(st_wdog_match, dev);

  	if (!match) {

  		dev_err(dev, "Couldn't match device
  ");

  		return -ENODEV;
  	}
  	st_wdog->syscfg	= (struct st_wdog_syscfg *)match->data;

  	base = devm_platform_ioremap_resource(pdev, 0);

  	if (IS_ERR(base))
  		return PTR_ERR(base);
  
  	regmap = syscon_regmap_lookup_by_phandle(np, "st,syscfg");
  	if (IS_ERR(regmap)) {

  		dev_err(dev, "No syscfg phandle specified
  ");

  		return PTR_ERR(regmap);
  	}

  	clk = devm_clk_get(dev, NULL);

  	if (IS_ERR(clk)) {

  		dev_err(dev, "Unable to request clock
  ");

  		return PTR_ERR(clk);
  	}

  	st_wdog->dev		= dev;

  	st_wdog->base		= base;
  	st_wdog->clk		= clk;
  	st_wdog->regmap		= regmap;
  	st_wdog->warm_reset	= of_property_read_bool(np, "st,warm_reset");
  	st_wdog->clkrate	= clk_get_rate(st_wdog->clk);
  
  	if (!st_wdog->clkrate) {

  		dev_err(dev, "Unable to fetch clock rate
  ");

  		return -EINVAL;
  	}
  	st_wdog_dev.max_timeout = 0xFFFFFFFF / st_wdog->clkrate;

  	st_wdog_dev.parent = dev;

  
  	ret = clk_prepare_enable(clk);
  	if (ret) {

  		dev_err(dev, "Unable to enable clock
  ");

  		return ret;
  	}

  	ret = devm_add_action_or_reset(dev, st_clk_disable_unprepare, clk);
  	if (ret)
  		return ret;

  
  	watchdog_set_drvdata(&st_wdog_dev, st_wdog);
  	watchdog_set_nowayout(&st_wdog_dev, WATCHDOG_NOWAYOUT);
  
  	/* Init Watchdog timeout with value in DT */

  	ret = watchdog_init_timeout(&st_wdog_dev, 0, dev);

  	if (ret)

  		return ret;

  	ret = devm_watchdog_register_device(dev, &st_wdog_dev);

  	if (ret)

  		return ret;

  
  	st_wdog_setup(st_wdog, true);

  	dev_info(dev, "LPC Watchdog driver registered, reset type is %s",

  		 st_wdog->warm_reset ? "warm" : "cold");
  
  	return ret;
  }
  
  static int st_wdog_remove(struct platform_device *pdev)
  {
  	struct st_wdog *st_wdog = watchdog_get_drvdata(&st_wdog_dev);
  
  	st_wdog_setup(st_wdog, false);

  
  	return 0;
  }
  
  #ifdef CONFIG_PM_SLEEP
  static int st_wdog_suspend(struct device *dev)
  {
  	struct st_wdog *st_wdog = watchdog_get_drvdata(&st_wdog_dev);
  
  	if (watchdog_active(&st_wdog_dev))
  		st_wdog_stop(&st_wdog_dev);
  
  	st_wdog_setup(st_wdog, false);
  
  	clk_disable(st_wdog->clk);
  
  	return 0;
  }
  
  static int st_wdog_resume(struct device *dev)
  {
  	struct st_wdog *st_wdog = watchdog_get_drvdata(&st_wdog_dev);
  	int ret;
  
  	ret = clk_enable(st_wdog->clk);
  	if (ret) {
  		dev_err(dev, "Unable to re-enable clock
  ");
  		watchdog_unregister_device(&st_wdog_dev);
  		clk_unprepare(st_wdog->clk);
  		return ret;
  	}
  
  	st_wdog_setup(st_wdog, true);
  
  	if (watchdog_active(&st_wdog_dev)) {
  		st_wdog_load_timer(st_wdog, st_wdog_dev.timeout);
  		st_wdog_start(&st_wdog_dev);
  	}
  
  	return 0;
  }
  #endif
  
  static SIMPLE_DEV_PM_OPS(st_wdog_pm_ops,
  			 st_wdog_suspend,
  			 st_wdog_resume);
  
  static struct platform_driver st_wdog_driver = {
  	.driver	= {
  		.name = "st-lpc-wdt",
  		.pm = &st_wdog_pm_ops,
  		.of_match_table = st_wdog_match,
  	},
  	.probe = st_wdog_probe,
  	.remove = st_wdog_remove,
  };
  module_platform_driver(st_wdog_driver);
  
  MODULE_AUTHOR("David Paris <david.paris@st.com>");
  MODULE_DESCRIPTION("ST LPC Watchdog Driver");
  MODULE_LICENSE("GPL");