Re: [PATCH v2 2/2] drm/msm/disp: Correct porch timing for SDM845

[Abhinav Kumar <quic_abhinavk@quicinc.com>]

On 2/12/2025 4:04 PM, Dmitry Baryshkov wrote:
> On Wed, Feb 12, 2025 at 03:03:47PM -0800, James A. MacInnes wrote:
>> Type-C DisplayPort inoperable due to incorrect porch settings.
>> - Re-used wide_bus_en as flag to prevent porch shifting
> 
> Unfortunately I don't know enough details to comment on this change.
> Maybe Abhinav can check it. I can only notice that msm-4.14 disables
> programmable_fetch_config for non-DSI calls. Would disabling that call
> for DP interface fix your issue?
> 

Yes, this piece of timing adjustment matches what we have even without 
widebus.

I do agree about the programmable fetch that it is enabled only on DSI 
even on the latest kernels.

698 	if (phys_enc->hw_intf->cap->type == INTF_DSI)
699 		programmable_fetch_config(phys_enc, &timing_params);

We can try if that works.

>>
>> Fixes: c943b4948b58 ("drm/msm/dp: add displayPort driver support")
>> Signed-off-by: James A. MacInnes <james.a.macinnes@gmail.com>
>> ---
>>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c | 14 +++++++++-----
>>   1 file changed, 9 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c
>> index abd6600046cb..a21addc4794f 100644
>> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c
>> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c
>> @@ -94,17 +94,21 @@ static void drm_mode_to_intf_timing_params(
>>   		timing->vsync_polarity = 0;
>>   	}
>>   
>> -	/* for DP/EDP, Shift timings to align it to bottom right */
>> -	if (phys_enc->hw_intf->cap->type == INTF_DP) {
>> +	timing->wide_bus_en = dpu_encoder_is_widebus_enabled(phys_enc->parent);
>> +	timing->compression_en = dpu_encoder_is_dsc_enabled(phys_enc->parent);
>> +
>> +	/*
>> +	 *  For DP/EDP, Shift timings to align it to bottom right.
>> +	 *  wide_bus_en is set for everything excluding SDM845 &
>> +	 *  porch changes cause DisplayPort failure and HDMI tearing.
>> +	 */
>> +	if (phys_enc->hw_intf->cap->type == INTF_DP && timing->wide_bus_en) {
>>   		timing->h_back_porch += timing->h_front_porch;
>>   		timing->h_front_porch = 0;
>>   		timing->v_back_porch += timing->v_front_porch;
>>   		timing->v_front_porch = 0;
>>   	}
>>   
>> -	timing->wide_bus_en = dpu_encoder_is_widebus_enabled(phys_enc->parent);
>> -	timing->compression_en = dpu_encoder_is_dsc_enabled(phys_enc->parent);
>> -
>>   	/*
>>   	 * for DP, divide the horizonal parameters by 2 when
>>   	 * widebus is enabled
>>
>> -- 
>> 2.43.0
>>
>