/*
   * Ralink MT7621/MT7628 built-in hardware watchdog timer
   *

   * Copyright (C) 2014 John Crispin <john@phrozen.org>

   *
   * This driver was based on: drivers/watchdog/rt2880_wdt.c
   *
   * 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.
   */
  
  #include <linux/clk.h>
  #include <linux/reset.h>
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/watchdog.h>
  #include <linux/moduleparam.h>
  #include <linux/platform_device.h>
  
  #include <asm/mach-ralink/ralink_regs.h>
  
  #define SYSC_RSTSTAT			0x38
  #define WDT_RST_CAUSE			BIT(1)
  
  #define RALINK_WDT_TIMEOUT		30
  
  #define TIMER_REG_TMRSTAT		0x00
  #define TIMER_REG_TMR1LOAD		0x24
  #define TIMER_REG_TMR1CTL		0x20
  
  #define TMR1CTL_ENABLE			BIT(7)
  #define TMR1CTL_RESTART			BIT(9)
  #define TMR1CTL_PRESCALE_SHIFT		16
  
  static void __iomem *mt7621_wdt_base;
  static struct reset_control *mt7621_wdt_reset;
  
  static bool nowayout = WATCHDOG_NOWAYOUT;
  module_param(nowayout, bool, 0);
  MODULE_PARM_DESC(nowayout,
  		 "Watchdog cannot be stopped once started (default="
  		 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  
  static inline void rt_wdt_w32(unsigned reg, u32 val)
  {
  	iowrite32(val, mt7621_wdt_base + reg);
  }
  
  static inline u32 rt_wdt_r32(unsigned reg)
  {
  	return ioread32(mt7621_wdt_base + reg);
  }
  
  static int mt7621_wdt_ping(struct watchdog_device *w)
  {
  	rt_wdt_w32(TIMER_REG_TMRSTAT, TMR1CTL_RESTART);
  
  	return 0;
  }
  
  static int mt7621_wdt_set_timeout(struct watchdog_device *w, unsigned int t)
  {
  	w->timeout = t;
  	rt_wdt_w32(TIMER_REG_TMR1LOAD, t * 1000);
  	mt7621_wdt_ping(w);
  
  	return 0;
  }
  
  static int mt7621_wdt_start(struct watchdog_device *w)
  {
  	u32 t;
  
  	/* set the prescaler to 1ms == 1000us */
  	rt_wdt_w32(TIMER_REG_TMR1CTL, 1000 << TMR1CTL_PRESCALE_SHIFT);
  
  	mt7621_wdt_set_timeout(w, w->timeout);
  
  	t = rt_wdt_r32(TIMER_REG_TMR1CTL);
  	t |= TMR1CTL_ENABLE;
  	rt_wdt_w32(TIMER_REG_TMR1CTL, t);
  
  	return 0;
  }
  
  static int mt7621_wdt_stop(struct watchdog_device *w)
  {
  	u32 t;
  
  	mt7621_wdt_ping(w);
  
  	t = rt_wdt_r32(TIMER_REG_TMR1CTL);
  	t &= ~TMR1CTL_ENABLE;
  	rt_wdt_w32(TIMER_REG_TMR1CTL, t);
  
  	return 0;
  }
  
  static int mt7621_wdt_bootcause(void)
  {
  	if (rt_sysc_r32(SYSC_RSTSTAT) & WDT_RST_CAUSE)
  		return WDIOF_CARDRESET;
  
  	return 0;
  }

  static const struct watchdog_info mt7621_wdt_info = {

  	.identity = "Mediatek Watchdog",
  	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
  };

  static const struct watchdog_ops mt7621_wdt_ops = {

  	.owner = THIS_MODULE,
  	.start = mt7621_wdt_start,
  	.stop = mt7621_wdt_stop,
  	.ping = mt7621_wdt_ping,
  	.set_timeout = mt7621_wdt_set_timeout,
  };
  
  static struct watchdog_device mt7621_wdt_dev = {
  	.info = &mt7621_wdt_info,
  	.ops = &mt7621_wdt_ops,
  	.min_timeout = 1,
  	.max_timeout = 0xfffful / 1000,
  };
  
  static int mt7621_wdt_probe(struct platform_device *pdev)
  {
  	struct resource *res;
  	int ret;
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	mt7621_wdt_base = devm_ioremap_resource(&pdev->dev, res);
  	if (IS_ERR(mt7621_wdt_base))
  		return PTR_ERR(mt7621_wdt_base);

  	mt7621_wdt_reset = devm_reset_control_get_exclusive(&pdev->dev, NULL);

  	if (!IS_ERR(mt7621_wdt_reset))
  		reset_control_deassert(mt7621_wdt_reset);

  	mt7621_wdt_dev.bootstatus = mt7621_wdt_bootcause();
  
  	watchdog_init_timeout(&mt7621_wdt_dev, mt7621_wdt_dev.max_timeout,
  			      &pdev->dev);
  	watchdog_set_nowayout(&mt7621_wdt_dev, nowayout);
  
  	ret = watchdog_register_device(&mt7621_wdt_dev);
  
  	return 0;
  }
  
  static int mt7621_wdt_remove(struct platform_device *pdev)
  {
  	watchdog_unregister_device(&mt7621_wdt_dev);
  
  	return 0;
  }
  
  static void mt7621_wdt_shutdown(struct platform_device *pdev)
  {
  	mt7621_wdt_stop(&mt7621_wdt_dev);
  }
  
  static const struct of_device_id mt7621_wdt_match[] = {
  	{ .compatible = "mediatek,mt7621-wdt" },
  	{},
  };
  MODULE_DEVICE_TABLE(of, mt7621_wdt_match);
  
  static struct platform_driver mt7621_wdt_driver = {
  	.probe		= mt7621_wdt_probe,
  	.remove		= mt7621_wdt_remove,
  	.shutdown	= mt7621_wdt_shutdown,
  	.driver		= {
  		.name		= KBUILD_MODNAME,
  		.of_match_table	= mt7621_wdt_match,
  	},
  };
  
  module_platform_driver(mt7621_wdt_driver);
  
  MODULE_DESCRIPTION("MediaTek MT762x hardware watchdog driver");

  MODULE_AUTHOR("John Crispin <john@phrozen.org");

  MODULE_LICENSE("GPL v2");