linux-kernel - Re: [PATCH v2 5/7] drm/msm/dp: return correct edid checksum after corrupted edid checksum read

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Date:   Thu, 29 Jul 2021 09:17:45 -0700
From:   khsieh@...eaurora.org
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     dri-devel@...ts.freedesktop.org, robdclark@...il.com,
        sean@...rly.run, abhinavk@...eaurora.org, aravindh@...eaurora.org,
        airlied@...ux.ie, daniel@...ll.ch, bjorn.andersson@...aro.org,
        linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/7] drm/msm/dp: return correct edid checksum after
 corrupted edid checksum read

On 2021-07-22 12:23, Stephen Boyd wrote:
> Quoting Kuogee Hsieh (2021-07-13 08:54:05)
>> diff --git a/drivers/gpu/drm/msm/dp/dp_panel.c 
>> b/drivers/gpu/drm/msm/dp/dp_panel.c
>> index 88196f7..0fdb551 100644
>> --- a/drivers/gpu/drm/msm/dp/dp_panel.c
>> +++ b/drivers/gpu/drm/msm/dp/dp_panel.c
>> @@ -303,7 +303,12 @@ void dp_panel_handle_sink_request(struct dp_panel 
>> *dp_panel)
>>         panel = container_of(dp_panel, struct dp_panel_private, 
>> dp_panel);
>> 
>>         if (panel->link->sink_request & DP_TEST_LINK_EDID_READ) {
>> -               u8 checksum = 
>> dp_panel_get_edid_checksum(dp_panel->edid);
>> +               u8 checksum;
>> +
>> +               if (dp_panel->edid)
>> +                       checksum = 
>> dp_panel_get_edid_checksum(dp_panel->edid);
>> +               else
>> +                       checksum = 
>> dp_panel->connector->real_edid_checksum;
> 
> Is there any reason why we can't use connector->real_edid_checksum all
> the time?
> 
real_edid_checksum only calculated by drm when edid checksum 
vitrification failed after edid read.
In the good edid checksum case (edid verification succeed), 
real_edid_checksum is not calculated by drm.
>> 
>>                 dp_link_send_edid_checksum(panel->link, checksum);
>>                 dp_link_send_test_response(panel->link);