Re: [PATCH v2] gpio: rockchip: resolve overflow issues

[Heiko Stübner <heiko@xxxxxxxxx>]

Am Freitag, 23. August 2024, 05:43:06 CEST schrieb Ye Zhang:
> Prevent overflow issues when performing debounce-related calculations.

Please add some more explanation here.
I.e. something about previous max_debounce calculation does overflow
the type of max_debounce

Thanks
Heiko

> Fixes: 3bcbd1a85b68 ("gpio/rockchip: support next version gpio controller")
> Signed-off-by: Ye Zhang <ye.zhang@xxxxxxxxxxxxxx>
> ---
>  drivers/gpio/gpio-rockchip.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpio/gpio-rockchip.c b/drivers/gpio/gpio-rockchip.c
> index 5f60162baaeb..bf22b103b6a2 100644
> --- a/drivers/gpio/gpio-rockchip.c
> +++ b/drivers/gpio/gpio-rockchip.c
> @@ -209,11 +209,12 @@ static int rockchip_gpio_set_debounce(struct gpio_chip *gc,
>  		freq = clk_get_rate(bank->db_clk);
>  		if (!freq)
>  			return -EINVAL;
> -		max_debounce = (GENMASK(23, 0) + 1) * 2 * 1000000 / freq;
> +		div = (u64)(GENMASK(23, 0) + 1) * 2 * 1000000;
> +		max_debounce = DIV_ROUND_CLOSEST_ULL(div, freq);
>  		if (debounce > max_debounce)
>  			return -EINVAL;
>  
> -		div = debounce * freq;
> +		div = (u64)debounce * freq;
>  		div_reg = DIV_ROUND_CLOSEST_ULL(div, 2 * USEC_PER_SEC) - 1;
>  	} else {
>  		div_debounce_support = false;
>