[PATCH v3 RESEND 2/5] watchdog: s3c2410_wdt: Fix max_timeout being calculated larger

[Alim Akhtar]

> -----Original Message-----
> From: Sangwook Shin <sw617.shin at samsung.com>
> Sent: Monday, July 14, 2025 11:25 AM
> To: krzk at kernel.org; alim.akhtar at samsung.com; wim at linux-watchdog.org;
> linux at roeck-us.net
> Cc: linux-arm-kernel at lists.infradead.org; linux-samsung-
> soc at vger.kernel.org; linux-watchdog at vger.kernel.org; linux-
> kernel at vger.kernel.org; Sangwook Shin <sw617.shin at samsung.com>
> Subject: [PATCH v3 RESEND 2/5] watchdog: s3c2410_wdt: Fix max_timeout
> being calculated larger
> 
> Fix the issue of max_timeout being calculated larger than actual value.
> The calculation result of freq / (S3C2410_WTCON_PRESCALE_MAX + 1) /
> S3C2410_WTCON_MAXDIV is smaller than the actual value because the
> remainder is discarded during the calculation process. This leads to a larger
> calculated value for max_timeout compared to the actual settable value.
> A ceiling operation is applied in the calculation process to resolve this.
> 
> Signed-off-by: Sangwook Shin <sw617.shin at samsung.com>
> ---
Reviewed-by: Alim Akhtar <alim.akhtar at samsung.com>

>  drivers/watchdog/s3c2410_wdt.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/watchdog/s3c2410_wdt.c
> b/drivers/watchdog/s3c2410_wdt.c index 95f7207e390a..31f7e1ec779e
> 100644
> --- a/drivers/watchdog/s3c2410_wdt.c
> +++ b/drivers/watchdog/s3c2410_wdt.c
> @@ -411,8 +411,8 @@ static inline unsigned int
> s3c2410wdt_max_timeout(struct s3c2410_wdt *wdt)  {
>  	const unsigned long freq = s3c2410wdt_get_freq(wdt);
> 
> -	return S3C2410_WTCNT_MAXCNT / (freq /
> (S3C2410_WTCON_PRESCALE_MAX + 1)
> -				       / S3C2410_WTCON_MAXDIV);
> +	return S3C2410_WTCNT_MAXCNT / DIV_ROUND_UP(freq,
> +		(S3C2410_WTCON_PRESCALE_MAX + 1) *
> S3C2410_WTCON_MAXDIV);
>  }
> 
>  static int s3c2410wdt_disable_wdt_reset(struct s3c2410_wdt *wdt, bool
> mask)
> --
> 2.25.1