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

[Jani Nikula]

On Tue, 26 Oct 2021, Ville Syrjälä <ville.syrjala at linux.intel.com> wrote:
> 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>

Thanks, pushed.

BR,
Jani.

>
>> ---
>>  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

-- 
Jani Nikula, Intel Open Source Graphics Center