linux-kernel - Re: [PATCH 29/45] drm/msm/dp: skip reading the EDID for MST cases

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Message-ID: <7khoxaafl2eclgqe2jfwgdmruvtoug5fpjdkvcrmpcynddnloa@toooyaio7rzm>
Date: Fri, 6 Dec 2024 11:32:44 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Abhinav Kumar <quic_abhinavk@...cinc.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>, Stephen Boyd <swboyd@...omium.org>, 
	Chandan Uddaraju <chandanu@...eaurora.org>, Guenter Roeck <groeck@...omium.org>, 
	Kuogee Hsieh <quic_khsieh@...cinc.com>, Bjorn Andersson <andersson@...nel.org>, 
	Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Vara Reddy <quic_varar@...cinc.com>, Rob Clark <robdclark@...omium.org>, 
	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, devicetree@...r.kernel.org, 
	Jessica Zhang <quic_jesszhan@...cinc.com>, Laurent Pinchart <laurent.pinchart@...asonboard.com>
Subject: Re: [PATCH 29/45] drm/msm/dp: skip reading the EDID for MST cases

On Thu, Dec 05, 2024 at 08:32:00PM -0800, Abhinav Kumar wrote:
> For MST cases, EDID is handled through AUX sideband messaging.
> Skip the EDID read during hotplug handle for MST cases.

But why? Isn't EDID being read at the hotplug time to update
drm_connector's data?

> 
> Signed-off-by: Abhinav Kumar <quic_abhinavk@...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 033d238e956263c1212fce45aab01316ef341edb..a67bc7c1b83a5a9996435804ff7337f72dae93a0 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -420,9 +420,11 @@ 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->max_stream <= DEFAULT_STREAM_COUNT || !msm_dp_panel_read_mst_cap(dp->panel)) {
> +		rc = msm_dp_panel_read_edid(dp->panel, connector);
> +		if (rc)
> +			goto end;
> +	}
>  
>  	msm_dp_link_process_request(dp->link);
>  
> 
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry