Re: [PATCH v6 3/5] watchdog: s3c2410_wdt: Increase max timeout value of watchdog

[Guenter Roeck <linux@roeck-us.net>]

On Mon, Aug 18, 2025 at 11:18:24AM +0900, Sangwook Shin wrote:
> Increase max_timeout value from 55s to 3665038s (1018h 3min 58s) with
> 38400000 frequency system if the system has 32-bit WTCNT register.
> 
> cat /sys/class/watchdog/watchdog0/max_timeout
> 3665038
> 
> [    0.330082] s3c2410-wdt 10060000.watchdog_cl0: Heartbeat: count=1099511400000, timeout=3665038, freq=300000
> [    0.330087] s3c2410-wdt 10060000.watchdog_cl0: Heartbeat: timeout=3665038, divisor=256, count=1099511400000 (fffffc87)
> [    0.330127] s3c2410-wdt 10060000.watchdog_cl0: starting watchdog timer
> [    0.330134] s3c2410-wdt 10060000.watchdog_cl0: Starting watchdog: count=0xfffffc87, wtcon=0001ff39
> [    0.330319] s3c2410-wdt 10060000.watchdog_cl0: watchdog active, reset enabled, irq disabled
> 
> If the system has a 32-bit WTCNT, add QUIRK_HAS_32BIT_CNT to its quirk flags,
> and it will operate with a 32-bit counter. If not, it will operate with a 16-bit
> counter like in the previous version.
> 
> Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>
> Signed-off-by: Sangwook Shin <sw617.shin@samsung.com>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> ---
>  drivers/watchdog/s3c2410_wdt.c | 26 +++++++++++++++++++-------
>  1 file changed, 19 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/watchdog/s3c2410_wdt.c b/drivers/watchdog/s3c2410_wdt.c
> index 1e8cf0299713..d983cbcb975c 100644
> --- a/drivers/watchdog/s3c2410_wdt.c
> +++ b/drivers/watchdog/s3c2410_wdt.c
> @@ -34,7 +34,8 @@
>  #define S3C2410_WTCNT		0x08
>  #define S3C2410_WTCLRINT	0x0c
>  
> -#define S3C2410_WTCNT_MAXCNT	0xffff
> +#define S3C2410_WTCNT_MAXCNT_16	0xffff
> +#define S3C2410_WTCNT_MAXCNT_32	0xffffffff
>  
>  #define S3C2410_WTCON_RSTEN		BIT(0)
>  #define S3C2410_WTCON_INTEN		BIT(2)
> @@ -124,6 +125,10 @@
>   * %QUIRK_HAS_DBGACK_BIT: WTCON register has DBGACK_MASK bit. Setting the
>   * DBGACK_MASK bit disables the watchdog outputs when the SoC is in debug mode.
>   * Debug mode is determined by the DBGACK CPU signal.
> + *
> + * %QUIRK_HAS_32BIT_CNT: WTDAT and WTCNT are 32-bit registers. With these
> + * 32-bit registers, larger values will be set, which means that larger timeouts
> + * value can be set.
>   */
>  #define QUIRK_HAS_WTCLRINT_REG			BIT(0)
>  #define QUIRK_HAS_PMU_MASK_RESET		BIT(1)
> @@ -131,6 +136,7 @@
>  #define QUIRK_HAS_PMU_AUTO_DISABLE		BIT(3)
>  #define QUIRK_HAS_PMU_CNT_EN			BIT(4)
>  #define QUIRK_HAS_DBGACK_BIT			BIT(5)
> +#define QUIRK_HAS_32BIT_CNT			BIT(6)
>  
>  /* These quirks require that we have a PMU register map */
>  #define QUIRKS_HAVE_PMUREG \
> @@ -199,6 +205,7 @@ struct s3c2410_wdt {
>  	struct notifier_block	freq_transition;
>  	const struct s3c2410_wdt_variant *drv_data;
>  	struct regmap *pmureg;
> +	u32 max_cnt;
>  };
>  
>  static const struct s3c2410_wdt_variant drv_data_s3c2410 = {
> @@ -412,7 +419,7 @@ static inline unsigned int s3c2410wdt_max_timeout(struct s3c2410_wdt *wdt)
>  {
>  	const unsigned long freq = s3c2410wdt_get_freq(wdt);
>  	const u64 n_max = (u64)(S3C2410_WTCON_PRESCALE_MAX + 1) *
> -			S3C2410_WTCON_MAXDIV * S3C2410_WTCNT_MAXCNT;
> +			S3C2410_WTCON_MAXDIV * wdt->max_cnt;
>  	u64 t_max = div64_ul(n_max, freq);
>  
>  	if (t_max > UINT_MAX)
> @@ -572,7 +579,7 @@ static int s3c2410wdt_set_heartbeat(struct watchdog_device *wdd,
>  {
>  	struct s3c2410_wdt *wdt = watchdog_get_drvdata(wdd);
>  	unsigned long freq = s3c2410wdt_get_freq(wdt);
> -	unsigned int count;
> +	unsigned long count;
>  	unsigned int divisor = 1;
>  	unsigned long wtcon;
>  
> @@ -582,7 +589,7 @@ static int s3c2410wdt_set_heartbeat(struct watchdog_device *wdd,
>  	freq = DIV_ROUND_UP(freq, 128);
>  	count = timeout * freq;
>  
> -	dev_dbg(wdt->dev, "Heartbeat: count=%d, timeout=%d, freq=%lu\n",
> +	dev_dbg(wdt->dev, "Heartbeat: count=%lu, timeout=%d, freq=%lu\n",
>  		count, timeout, freq);
>  
>  	/* if the count is bigger than the watchdog register,
> @@ -590,8 +597,8 @@ static int s3c2410wdt_set_heartbeat(struct watchdog_device *wdd,
>  	   actually make this value
>  	*/
>  
> -	if (count >= 0x10000) {
> -		divisor = DIV_ROUND_UP(count, 0xffff);
> +	if (count > wdt->max_cnt) {
> +		divisor = DIV_ROUND_UP(count, wdt->max_cnt);
>  
>  		if (divisor > S3C2410_WTCON_PRESCALE_MAX + 1) {
>  			dev_err(wdt->dev, "timeout %d too big\n", timeout);
> @@ -599,7 +606,7 @@ static int s3c2410wdt_set_heartbeat(struct watchdog_device *wdd,
>  		}
>  	}
>  
> -	dev_dbg(wdt->dev, "Heartbeat: timeout=%d, divisor=%d, count=%d (%08x)\n",
> +	dev_dbg(wdt->dev, "Heartbeat: timeout=%d, divisor=%d, count=%lu (%08lx)\n",
>  		timeout, divisor, count, DIV_ROUND_UP(count, divisor));
>  
>  	count = DIV_ROUND_UP(count, divisor);
> @@ -807,6 +814,11 @@ static int s3c2410wdt_probe(struct platform_device *pdev)
>  	if (IS_ERR(wdt->src_clk))
>  		return dev_err_probe(dev, PTR_ERR(wdt->src_clk), "failed to get source clock\n");
>  
> +	if (wdt->drv_data->quirks & QUIRK_HAS_32BIT_CNT)
> +		wdt->max_cnt = S3C2410_WTCNT_MAXCNT_32;
> +	else
> +		wdt->max_cnt = S3C2410_WTCNT_MAXCNT_16;
> +
>  	wdt->wdt_device.min_timeout = 1;
>  	wdt->wdt_device.max_timeout = s3c2410wdt_max_timeout(wdt);
>  
> -- 
> 2.25.1
> 
>