Re: [PATCH 2/3] watchdog: sama5d4_wdt: Refactor the driver

[Alexandre Belloni <alexandre.belloni@bootlin.com>]

On 27/02/2026 13:01:15+0530, Balakrishnan Sambath wrote:
> From: Andrei Simion <andrei.simion@microchip.com>
> 
> This patch cleans up and refactors the Atmel SAMA5D4 Watchdog Driver
> to be more readable and to fixup Reset issue introduced
> by commit 266da53c35fc ("watchdog: sama5d4: readout initial state").
> 
> Signed-off-by: Andrei Simion <andrei.simion@microchip.com>
> [Use per-device WDDIS mask and sync MR shadow WDDIS state]
> Signed-off-by: Balakrishnan Sambath <balakrishnan.s@microchip.com>
> ---
>  drivers/watchdog/sama5d4_wdt.c | 156 ++++++++++++++++-----------------
>  1 file changed, 77 insertions(+), 79 deletions(-)
> 
> diff --git a/drivers/watchdog/sama5d4_wdt.c b/drivers/watchdog/sama5d4_wdt.c
> index 13e72918338a..b422d0bd75f9 100644
> --- a/drivers/watchdog/sama5d4_wdt.c
> +++ b/drivers/watchdog/sama5d4_wdt.c
> @@ -24,44 +24,58 @@
>  #define WDT_DEFAULT_TIMEOUT	MAX_WDT_TIMEOUT
>  
>  #define WDT_SEC2TICKS(s)	((s) ? (((s) << 8) - 1) : 0)
>  
>  struct sama5d4_wdt {
>  	struct watchdog_device	wdd;
>  	void __iomem		*reg_base;
>  	u32			mr;
>  	u32			ir;
> +	u32			wddis_mask;

Introducing this should simply remove the need for 3/3, use this instead
of AT91_WDT_WDDIS everywhere.

>  	unsigned long		last_ping;
>  	bool			need_irq;
> -	bool			sam9x60_support;
> +	bool			is_modern_chip;

The previous name was better.

>  };
>  
> +static inline bool wdt_enabled(struct sama5d4_wdt *wdt, u32 mr)
> +{
> +	return !(mr & wdt->wddis_mask);
> +}
> +

This is unrelated to the actual fix. This patch does to much and is
difficult to review and to backport, please separate the actual fix
about wddis and the rest.


>  static int wdt_timeout;
>  static bool nowayout = WATCHDOG_NOWAYOUT;
>  
>  module_param(wdt_timeout, int, 0);
>  MODULE_PARM_DESC(wdt_timeout,
>  	"Watchdog timeout in seconds. (default = "
>  	__MODULE_STRING(WDT_DEFAULT_TIMEOUT) ")");
>  
>  module_param(nowayout, bool, 0);
>  MODULE_PARM_DESC(nowayout,
>  	"Watchdog cannot be stopped once started (default="
>  	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
>  
> -#define wdt_enabled (!(wdt->mr & AT91_WDT_WDDIS))
>  
>  #define wdt_read(wdt, field) \
>  	readl_relaxed((wdt)->reg_base + (field))
>  
>  /* 4 slow clock periods is 4/32768 = 122.07µs*/
>  #define WDT_DELAY	usecs_to_jiffies(123)
>  
> +static bool check_is_modern_chip_by_compatible(struct device *dev)
> +{
> +	if (of_device_is_compatible(dev->of_node, "microchip,sam9x60-wdt") ||
> +	    of_device_is_compatible(dev->of_node, "microchip,sama7g5-wdt"))
> +		return true;
> +
> +	return false;
> +}
> +
>  static void wdt_write(struct sama5d4_wdt *wdt, u32 field, u32 val)
>  {
>  	/*
>  	 * WDT_CR and WDT_MR must not be modified within three slow clock
>  	 * periods following a restart of the watchdog performed by a write
>  	 * access in WDT_CR.
>  	 */
>  	while (time_before(jiffies, wdt->last_ping + WDT_DELAY))
>  		usleep_range(30, 125);
> @@ -71,322 +85,306 @@ static void wdt_write(struct sama5d4_wdt *wdt, u32 field, u32 val)
>  
>  static void wdt_write_nosleep(struct sama5d4_wdt *wdt, u32 field, u32 val)
>  {
>  	if (time_before(jiffies, wdt->last_ping + WDT_DELAY))
>  		udelay(123);
>  	writel_relaxed(val, wdt->reg_base + field);
>  	wdt->last_ping = jiffies;
>  }
>  
> -static int sama5d4_wdt_start(struct watchdog_device *wdd)
> +static int wdt_start(struct watchdog_device *wdd)
>  {
>  	struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
>  
> -	if (wdt->sam9x60_support) {
> -		writel_relaxed(wdt->ir, wdt->reg_base + AT91_SAM9X60_IER);
> -		wdt->mr &= ~AT91_SAM9X60_WDDIS;
> -	} else {
> -		wdt->mr &= ~AT91_WDT_WDDIS;
> -	}
> +	if (wdt->is_modern_chip)
> +		writel_relaxed(wdt->ir, wdt->reg_base + AT91_WDT_IER);
> +	wdt->mr &= ~wdt->wddis_mask;
>  	wdt_write(wdt, AT91_WDT_MR, wdt->mr);
>  
>  	return 0;
>  }
>  
> -static int sama5d4_wdt_stop(struct watchdog_device *wdd)
> +static int wdt_stop(struct watchdog_device *wdd)
>  {
>  	struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
>  
> -	if (wdt->sam9x60_support) {
> -		writel_relaxed(wdt->ir, wdt->reg_base + AT91_SAM9X60_IDR);
> -		wdt->mr |= AT91_SAM9X60_WDDIS;
> -	} else {
> -		wdt->mr |= AT91_WDT_WDDIS;
> -	}
> +	if (wdt->is_modern_chip)
> +		writel_relaxed(wdt->ir, wdt->reg_base + AT91_WDT_IDR);
> +	wdt->mr |= wdt->wddis_mask;
>  	wdt_write(wdt, AT91_WDT_MR, wdt->mr);
>  
>  	return 0;
>  }
>  
> -static int sama5d4_wdt_ping(struct watchdog_device *wdd)
> +static int wdt_ping(struct watchdog_device *wdd)
>  {
>  	struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
>  
>  	wdt_write(wdt, AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
>  
>  	return 0;
>  }
>  
> -static int sama5d4_wdt_set_timeout(struct watchdog_device *wdd,
> -				 unsigned int timeout)
> +static int wdt_set_timeout(struct watchdog_device *wdd,
> +			   unsigned int timeout)
>  {
>  	struct sama5d4_wdt *wdt = watchdog_get_drvdata(wdd);
>  	u32 value = WDT_SEC2TICKS(timeout);
>  
> -	if (wdt->sam9x60_support) {
> -		wdt_write(wdt, AT91_SAM9X60_WLR,
> -			  AT91_SAM9X60_SET_COUNTER(value));
> +	if (wdt->is_modern_chip) {
> +		wdt_write(wdt, AT91_WDT_WLR,
> +			  AT91_WDT_SET_COUNTER(value));
>  
>  		wdd->timeout = timeout;
>  		return 0;
>  	}
>  
>  	wdt->mr &= ~AT91_WDT_WDV;
>  	wdt->mr |= AT91_WDT_SET_WDV(value);
>  
>  	/*
>  	 * WDDIS has to be 0 when updating WDD/WDV. The datasheet states: When
>  	 * setting the WDDIS bit, and while it is set, the fields WDV and WDD
>  	 * must not be modified.
>  	 * If the watchdog is enabled, then the timeout can be updated. Else,
>  	 * wait that the user enables it.
>  	 */
> -	if (wdt_enabled)
> -		wdt_write(wdt, AT91_WDT_MR, wdt->mr & ~AT91_WDT_WDDIS);
> +	if (wdt_enabled(wdt, wdt->mr))
> +		wdt_write(wdt, AT91_WDT_MR, wdt->mr & ~wdt->wddis_mask);
>  
>  	wdd->timeout = timeout;
>  
>  	return 0;
>  }
>  
>  static const struct watchdog_info sama5d4_wdt_info = {
>  	.options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
>  	.identity = "Atmel SAMA5D4 Watchdog",
>  };
>  
>  static const struct watchdog_ops sama5d4_wdt_ops = {
>  	.owner = THIS_MODULE,
> -	.start = sama5d4_wdt_start,
> -	.stop = sama5d4_wdt_stop,
> -	.ping = sama5d4_wdt_ping,
> -	.set_timeout = sama5d4_wdt_set_timeout,
> +	.start = wdt_start,
> +	.stop = wdt_stop,
> +	.ping = wdt_ping,
> +	.set_timeout = wdt_set_timeout,
>  };
>  
> -static irqreturn_t sama5d4_wdt_irq_handler(int irq, void *dev_id)
> +static irqreturn_t wdt_irq_handler(int irq, void *dev_id)
>  {
>  	struct sama5d4_wdt *wdt = platform_get_drvdata(dev_id);
>  	u32 reg;
>  
> -	if (wdt->sam9x60_support)
> -		reg = wdt_read(wdt, AT91_SAM9X60_ISR);
> +	if (wdt->is_modern_chip)
> +		reg = wdt_read(wdt, AT91_WDT_ISR);
>  	else
>  		reg = wdt_read(wdt, AT91_WDT_SR);
>  
>  	if (reg) {
>  		pr_crit("Atmel Watchdog Software Reset\n");
>  		emergency_restart();
>  		pr_crit("Reboot didn't succeed\n");
>  	}
>  
>  	return IRQ_HANDLED;
>  }
>  
> -static int of_sama5d4_wdt_init(struct device_node *np, struct sama5d4_wdt *wdt)
> +static int of_wdt_init(struct device_node *np, struct sama5d4_wdt *wdt)
>  {
>  	const char *tmp;
>  
> -	if (wdt->sam9x60_support)
> -		wdt->mr = AT91_SAM9X60_WDDIS;
> -	else
> -		wdt->mr = AT91_WDT_WDDIS;
> +	wdt->mr = wdt->wddis_mask;
>  
>  	if (!of_property_read_string(np, "atmel,watchdog-type", &tmp) &&
>  	    !strcmp(tmp, "software"))
>  		wdt->need_irq = true;
>  
>  	if (of_property_read_bool(np, "atmel,idle-halt"))
>  		wdt->mr |= AT91_WDT_WDIDLEHLT;
>  
>  	if (of_property_read_bool(np, "atmel,dbg-halt"))
>  		wdt->mr |= AT91_WDT_WDDBGHLT;
>  
>  	return 0;
>  }
>  
> -static int sama5d4_wdt_init(struct sama5d4_wdt *wdt)
> +static int wdt_init(struct sama5d4_wdt *wdt)
>  {
> +	struct watchdog_device *wdd = &wdt->wdd;
>  	u32 reg, val;
>  
>  	val = WDT_SEC2TICKS(WDT_DEFAULT_TIMEOUT);
> +
>  	/*
>  	 * When booting and resuming, the bootloader may have changed the
>  	 * watchdog configuration.
> -	 * If the watchdog is already running, we can safely update it.
> -	 * Else, we have to disable it properly.
> +	 * If the watchdog is not running, we need to disable it properly.
> +	 * Otherwise, we can safely update it.
>  	 */
> -	if (!wdt_enabled) {
> -		reg = wdt_read(wdt, AT91_WDT_MR);
> -		if (wdt->sam9x60_support && (!(reg & AT91_SAM9X60_WDDIS)))
> -			wdt_write_nosleep(wdt, AT91_WDT_MR,
> -					  reg | AT91_SAM9X60_WDDIS);
> -		else if (!wdt->sam9x60_support &&
> -			 (!(reg & AT91_WDT_WDDIS)))
> -			wdt_write_nosleep(wdt, AT91_WDT_MR,
> -					  reg | AT91_WDT_WDDIS);
> +	reg = wdt_read(wdt, AT91_WDT_MR);
> +	if (wdt_enabled(wdt, reg)) {
> +		wdt->mr &= ~wdt->wddis_mask;
> +		set_bit(WDOG_HW_RUNNING, &wdd->status);
> +	} else {
> +		wdt->mr |= wdt->wddis_mask;
>  	}
>  
> -	if (wdt->sam9x60_support) {
> +	if (wdt->is_modern_chip) {
>  		if (wdt->need_irq)
> -			wdt->ir = AT91_SAM9X60_PERINT;
> +			wdt->ir = AT91_WDT_PERINT;
>  		else
> -			wdt->mr |= AT91_SAM9X60_PERIODRST;
> +			wdt->mr |= AT91_WDT_PERIODRST;
>  
> -		wdt_write(wdt, AT91_SAM9X60_IER, wdt->ir);
> -		wdt_write(wdt, AT91_SAM9X60_WLR, AT91_SAM9X60_SET_COUNTER(val));
> +		wdt_write(wdt, AT91_WDT_IER, wdt->ir);
> +		wdt_write(wdt, AT91_WDT_WLR, AT91_WDT_SET_COUNTER(val));
>  	} else {
>  		wdt->mr |= AT91_WDT_SET_WDD(WDT_SEC2TICKS(MAX_WDT_TIMEOUT));
>  		wdt->mr |= AT91_WDT_SET_WDV(val);
>  
>  		if (wdt->need_irq)
>  			wdt->mr |= AT91_WDT_WDFIEN;
>  		else
>  			wdt->mr |= AT91_WDT_WDRSTEN;
>  	}
>  
>  	wdt_write_nosleep(wdt, AT91_WDT_MR, wdt->mr);
>  
>  	return 0;
>  }
>  
> -static int sama5d4_wdt_probe(struct platform_device *pdev)
> +static int wdt_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
>  	struct watchdog_device *wdd;
>  	struct sama5d4_wdt *wdt;
>  	void __iomem *regs;
>  	u32 irq = 0;
> -	u32 reg;
>  	int ret;
>  
>  	wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
>  	if (!wdt)
>  		return -ENOMEM;
>  
>  	wdd = &wdt->wdd;
>  	wdd->timeout = WDT_DEFAULT_TIMEOUT;
>  	wdd->info = &sama5d4_wdt_info;
>  	wdd->ops = &sama5d4_wdt_ops;
>  	wdd->min_timeout = MIN_WDT_TIMEOUT;
>  	wdd->max_timeout = MAX_WDT_TIMEOUT;
>  	wdt->last_ping = jiffies;
> -
> -	if (of_device_is_compatible(dev->of_node, "microchip,sam9x60-wdt") ||
> -	    of_device_is_compatible(dev->of_node, "microchip,sama7g5-wdt"))
> -		wdt->sam9x60_support = true;
> +	wdt->is_modern_chip = check_is_modern_chip_by_compatible(dev);
> +	if (wdt->is_modern_chip)
> +		wdt->wddis_mask = AT91_WDT_WDDIS_MODERN;
> +	else
> +		wdt->wddis_mask = AT91_WDT_WDDIS_LEGACY;
>  
>  	watchdog_set_drvdata(wdd, wdt);
>  
>  	regs = devm_platform_ioremap_resource(pdev, 0);
>  	if (IS_ERR(regs))
>  		return PTR_ERR(regs);
>  
>  	wdt->reg_base = regs;
>  
> -	ret = of_sama5d4_wdt_init(dev->of_node, wdt);
> +	ret = of_wdt_init(dev->of_node, wdt);
>  	if (ret)
>  		return ret;
>  
>  	if (wdt->need_irq) {
>  		irq = irq_of_parse_and_map(dev->of_node, 0);
>  		if (!irq) {
>  			dev_warn(dev, "failed to get IRQ from DT\n");
>  			wdt->need_irq = false;
>  		}
>  	}
>  
>  	if (wdt->need_irq) {
> -		ret = devm_request_irq(dev, irq, sama5d4_wdt_irq_handler,
> +		ret = devm_request_irq(dev, irq, wdt_irq_handler,
>  				       IRQF_SHARED | IRQF_IRQPOLL |
>  				       IRQF_NO_SUSPEND, pdev->name, pdev);
>  		if (ret) {
>  			dev_err(dev, "cannot register interrupt handler\n");
>  			return ret;
>  		}
>  	}
>  
>  	watchdog_init_timeout(wdd, wdt_timeout, dev);
>  
> -	reg = wdt_read(wdt, AT91_WDT_MR);
> -	if (!(reg & AT91_WDT_WDDIS)) {
> -		wdt->mr &= ~AT91_WDT_WDDIS;
> -		set_bit(WDOG_HW_RUNNING, &wdd->status);
> -	}
> -
> -	ret = sama5d4_wdt_init(wdt);
> +	ret = wdt_init(wdt);
>  	if (ret)
>  		return ret;
>  
>  	watchdog_set_nowayout(wdd, nowayout);
>  
>  	watchdog_stop_on_unregister(wdd);
>  	ret = devm_watchdog_register_device(dev, wdd);
>  	if (ret)
>  		return ret;
>  
>  	platform_set_drvdata(pdev, wdt);
>  
>  	dev_info(dev, "initialized (timeout = %d sec, nowayout = %d)\n",
>  		 wdd->timeout, nowayout);
>  
>  	return 0;
>  }
>  
> -static const struct of_device_id sama5d4_wdt_of_match[] = {
> +static const struct of_device_id wdt_of_match[] = {
>  	{
>  		.compatible = "atmel,sama5d4-wdt",
>  	},
>  	{
>  		.compatible = "microchip,sam9x60-wdt",
>  	},
>  	{
>  		.compatible = "microchip,sama7g5-wdt",
>  	},
>  
>  	{ }
>  };
> -MODULE_DEVICE_TABLE(of, sama5d4_wdt_of_match);
> +MODULE_DEVICE_TABLE(of, wdt_of_match);
>  
> -static int sama5d4_wdt_suspend_late(struct device *dev)
> +static int wdt_suspend_late(struct device *dev)
>  {
>  	struct sama5d4_wdt *wdt = dev_get_drvdata(dev);
>  
>  	if (watchdog_active(&wdt->wdd))
> -		sama5d4_wdt_stop(&wdt->wdd);
> +		wdt_stop(&wdt->wdd);
>  
>  	return 0;
>  }
>  
> -static int sama5d4_wdt_resume_early(struct device *dev)
> +static int wdt_resume_early(struct device *dev)
>  {
>  	struct sama5d4_wdt *wdt = dev_get_drvdata(dev);
>  
>  	/*
>  	 * FIXME: writing MR also pings the watchdog which may not be desired.
>  	 * This should only be done when the registers are lost on suspend but
>  	 * there is no way to get this information right now.
>  	 */
> -	sama5d4_wdt_init(wdt);
> +	wdt_init(wdt);
>  
>  	if (watchdog_active(&wdt->wdd))
> -		sama5d4_wdt_start(&wdt->wdd);
> +		wdt_start(&wdt->wdd);
>  
>  	return 0;
>  }
>  
>  static const struct dev_pm_ops sama5d4_wdt_pm_ops = {
> -	LATE_SYSTEM_SLEEP_PM_OPS(sama5d4_wdt_suspend_late,
> -				 sama5d4_wdt_resume_early)
> +	LATE_SYSTEM_SLEEP_PM_OPS(wdt_suspend_late,
> +				 wdt_resume_early)
>  };
>  
>  static struct platform_driver sama5d4_wdt_driver = {
> -	.probe		= sama5d4_wdt_probe,
> +	.probe		= wdt_probe,
>  	.driver		= {
>  		.name	= "sama5d4_wdt",
>  		.pm	= pm_sleep_ptr(&sama5d4_wdt_pm_ops),
> -		.of_match_table = sama5d4_wdt_of_match,
> +		.of_match_table = wdt_of_match,
>  	}
>  };
>  module_platform_driver(sama5d4_wdt_driver);
>  
>  MODULE_AUTHOR("Atmel Corporation");
>  MODULE_DESCRIPTION("Atmel SAMA5D4 Watchdog Timer driver");
>  MODULE_LICENSE("GPL v2");
> -- 
> 2.34.1
> 

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com