[Intel-gfx] [PATCH v2] drm/i915/dp: fix integer overflow in 128b/132b data rate calculation

[Ville Syrjälä]

On Tue, Oct 26, 2021 at 12:34:07PM +0300, Jani Nikula wrote:
> The intermediate value 1000000 * 10 * 9671 overflows 32 bits, so force
> promotion to a bigger type.
> 
> >From the logs:
> 
> [drm:intel_dp_compute_config [i915]] DP link rate required 3657063 available -580783288
> 
> v2: Use mul_u32_u32() (Ville)
> 
> Fixes: 48efd014f0ea ("drm/i915/dp: add max data rate calculation for UHBR rates")
> Cc: Manasi Navare <manasi.d.navare at intel.com>
> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> Signed-off-by: Jani Nikula <jani.nikula at intel.com>

Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index f5dc2126d140..537c689a1528 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -352,7 +352,7 @@ intel_dp_max_data_rate(int max_link_rate, int max_lanes)
>  		 */
>  		int max_link_rate_kbps = max_link_rate * 10;
>  
> -		max_link_rate_kbps = DIV_ROUND_CLOSEST_ULL(max_link_rate_kbps * 9671, 10000);
> +		max_link_rate_kbps = DIV_ROUND_CLOSEST_ULL(mul_u32_u32(max_link_rate_kbps, 9671), 10000);
>  		max_link_rate = max_link_rate_kbps / 8;
>  	}
>  
> -- 
> 2.30.2

-- 
Ville Syrjälä
Intel