linux-kernel - Re: [PATCH v2 26/38] drm/msm/dp: skip reading the EDID for MST cases

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Message-ID: <e3b5721d-cf37-4b35-9851-5e822fa16c09@quicinc.com>
Date: Thu, 14 Aug 2025 16:22:44 +0800
From: Yongxing Mou <quic_yongmou@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
CC: Rob Clark <robin.clark@....qualcomm.com>,
        Abhinav Kumar
	<abhinav.kumar@...ux.dev>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        "Abhinav
 Kumar" <quic_abhinavk@...cinc.com>
Subject: Re: [PATCH v2 26/38] drm/msm/dp: skip reading the EDID for MST cases



On 2025/6/9 23:58, Dmitry Baryshkov wrote:
> On Mon, Jun 09, 2025 at 08:21:45PM +0800, Yongxing Mou wrote:
>> From: Abhinav Kumar <quic_abhinavk@...cinc.com>
>>
>> For MST cases, EDID is handled through AUX sideband messaging.
>> Skip the EDID read during hotplug handle for MST cases.
> 
> Why? It makes sense to read it during the HPD processing, ping HDMI
> codec, update CEC info, etc.
> 
For MST case to read EDID. we will use drm_dp_mst_edid_read when MST 
connetors .get_modes() called.
>>
>> Signed-off-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
>> Signed-off-by: Yongxing Mou <quic_yongmou@...cinc.com>
>> ---
>>   drivers/gpu/drm/msm/dp/dp_display.c | 8 +++++---
>>   1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
>> index 88cae0ca66015377e59bee757462edeae5ae91bf..b1b025d1d356046f8f9e3d243fc774185df24318 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_display.c
>> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
>> @@ -438,9 +438,11 @@ static int msm_dp_display_process_hpd_high(struct msm_dp_display_private *dp)
>>   	if (rc)
>>   		goto end;
>>   
>> -	rc = msm_dp_panel_read_edid(dp->panel, connector);
>> -	if (rc)
>> -		goto end;
>> +	if (!dp->mst_supported || !drm_dp_read_mst_cap(dp->aux, dp->panel->dpcd)) {
>> +		rc = msm_dp_panel_read_edid(dp->panel, connector);
>> +		if (rc)
>> +			goto end;
>> +	}
>>   
>>   	msm_dp_link_process_request(dp->link);
>>   
>>
>> -- 
>> 2.34.1
>>
>