On Mon, Aug 18, 2025 at 11:18:23AM +0900, Sangwook Shin wrote:
> 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.
> To resolve this issue, the order of calculations in the computation process
> has been adjusted.
>
> Reviewed-by: Sam Protsenko <semen.protsenko@xxxxxxxxxx>
> Signed-off-by: Sangwook Shin <sw617.shin@xxxxxxxxxxx>
Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> ---
> drivers/watchdog/s3c2410_wdt.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/watchdog/s3c2410_wdt.c b/drivers/watchdog/s3c2410_wdt.c
> index 95f7207e390a..1e8cf0299713 100644
> --- a/drivers/watchdog/s3c2410_wdt.c
> +++ b/drivers/watchdog/s3c2410_wdt.c
> @@ -27,6 +27,7 @@
> #include <linux/mfd/syscon.h>
> #include <linux/regmap.h>
> #include <linux/delay.h>
> +#include <linux/math64.h>
>
> #define S3C2410_WTCON 0x00
> #define S3C2410_WTDAT 0x04
> @@ -410,9 +411,14 @@ static inline unsigned long s3c2410wdt_get_freq(struct s3c2410_wdt *wdt)
> 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;
> + u64 t_max = div64_ul(n_max, freq);
>
> - return S3C2410_WTCNT_MAXCNT / (freq / (S3C2410_WTCON_PRESCALE_MAX + 1)
> - / S3C2410_WTCON_MAXDIV);
> + if (t_max > UINT_MAX)
> + t_max = UINT_MAX;
> +
> + return t_max;
> }
>
> static int s3c2410wdt_disable_wdt_reset(struct s3c2410_wdt *wdt, bool mask)
> --
> 2.25.1
>
>
