[PATCH 05/19] drm/i915/dp: Update Bigjoiner interface bits for computing compressed bpp

[Nautiyal, Ankit K]

Hi Stan,

Thanks for the reviews ans suggestions. Please my response inline:


On 7/20/2023 2:59 PM, Lisovskiy, Stanislav wrote:
> On Thu, Jul 13, 2023 at 04:03:32PM +0530, Ankit Nautiyal wrote:
>> In Bigjoiner check for DSC, bigjoiner interface bits for DP for
>> DISPLAY > 13 is 36 (Bspec: 49259).
>>
>> v2: Corrected Display ver to 13.
>>
>> v3: Follow convention for conditional statement. (Ville)
>>
>> v4: Fix check for display ver. (Ville)
>>
>> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
>> Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
>> ---
>>   drivers/gpu/drm/i915/display/intel_dp.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
>> index 19768ac658ba..c1fd448d80e1 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> @@ -802,8 +802,9 @@ u16 intel_dp_dsc_get_max_compressed_bpp(struct drm_i915_private *i915,
>>   	bits_per_pixel = min(bits_per_pixel, max_bpp_small_joiner_ram);
>>   
>>   	if (bigjoiner) {
>> +		int bigjoiner_interface_bits = DISPLAY_VER(i915) >= 14 ? 36 : 24;
>>   		u32 max_bpp_bigjoiner =
>> -			i915->display.cdclk.max_cdclk_freq * 48 /
>> +			i915->display.cdclk.max_cdclk_freq * 2 * bigjoiner_interface_bits /
> Probably "num_vdsc_instances = intel_dsc_get_num_vdsc_instances(crtc_state);" again,
> instead of "2"?

Currently intel_dsc_get_num_vdsc_instances will give total number of 
vdsc_engines including joined pipes.

So with bigjoiner the function will return 4.

This was good to calculate Pipe BW check: (Pixel clock < PPC * CDCLK 
frequency * Number of pipes joined

as we get PPC * number of pipes joined from 
intel_dsc_get_num_vdsc_instances)

Or to calculate DSC_PIC_WIDTH PPS parameter.

But here we perhaps need intel_dsc_get_vdsc_engines_per_pipe that will 
just return 2 if dsc_split 1 otherwise.

Thanks & Regards,

Ankit

>
> With that clarified,
>
> Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
>
>>   			intel_dp_mode_to_fec_clock(mode_clock);
>>   
>>   		bits_per_pixel = min(bits_per_pixel, max_bpp_bigjoiner);
>> -- 
>> 2.40.1
>>