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

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Message-ID: <244931ee-acaa-4973-bb8e-aa4c6c1609f0@quicinc.com>
Date: Wed, 12 Feb 2025 19:23:55 -0800
From: Abhinav Kumar <quic_abhinavk@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        "James A. MacInnes"
	<james.a.macinnes@...il.com>
CC: Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        "Marijn
 Suijten" <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Chandan Uddaraju <chandanu@...eaurora.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Vara Reddy <quic_varar@...cinc.com>,
        Tanmay Shah <tanmay@...eaurora.org>, <linux-arm-msm@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>, <freedreno@...ts.freedesktop.org>,
        <linux-kernel@...r.kernel.org>, Guenter Roeck <groeck@...omium.org>,
        "Rob
 Clark" <robdclark@...omium.org>
Subject: Re: [PATCH v2 2/2] drm/msm/disp: Correct porch timing for SDM845



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@...il.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
>>
>