linux-kernel - Re: [PATCH v3 6/6] drm: panel-backlight-quirks: Log applied panel brightness quirks

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Message-ID: <588626d9-eb27-4376-8741-a1cc2e2e17cf@kernel.org>
Date: Tue, 2 Sep 2025 23:52:30 -0500
From: Mario Limonciello <superm1@...nel.org>
To: Antheas Kapenekakis <lkml@...heas.dev>, amd-gfx@...ts.freedesktop.org
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 philm@...jaro.org, Alex Deucher <alexander.deucher@....com>,
 Christian König <christian.koenig@....com>,
 Robert Beckett <bob.beckett@...labora.com>
Subject: Re: [PATCH v3 6/6] drm: panel-backlight-quirks: Log applied panel
 brightness quirks

On 8/29/2025 10:01 AM, Antheas Kapenekakis wrote:
> On Fri, 29 Aug 2025 at 16:57, Antheas Kapenekakis <lkml@...heas.dev> wrote:
>>
>> Currently, when a panel brightness quirk is applied, there is no log
>> indicating that a quirk was applied. Unwrap the drm device on its own
>> and use drm_info() to log when a quirk is applied.
>>
>> Suggested-by: Mario Limonciello <mario.limonciello@....com>
>> Signed-off-by: Antheas Kapenekakis <lkml@...heas.dev>
>> ---
>>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c    | 16 +++++++++++++---
>>   1 file changed, 13 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> index 263f15f6fdea..2a3e17d83d6e 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> @@ -3617,13 +3617,15 @@ static void update_connector_ext_caps(struct amdgpu_dm_connector *aconnector)
>>          struct drm_connector *conn_base;
>>          struct amdgpu_device *adev;
>>          struct drm_luminance_range_info *luminance_range;
>> +       struct drm_device *drm;
>>
>>          if (aconnector->bl_idx == -1 ||
>>              aconnector->dc_link->connector_signal != SIGNAL_TYPE_EDP)
>>                  return;
>>
>>          conn_base = &aconnector->base;
>> -       adev = drm_to_adev(conn_base->dev);
>> +       drm = conn_base->dev;
>> +       adev = drm_to_adev(drm);
>>
>>          caps = &adev->dm.backlight_caps[aconnector->bl_idx];
>>          caps->ext_caps = &aconnector->dc_link->dpcd_sink_ext_caps;
>> @@ -3659,12 +3661,20 @@ static void update_connector_ext_caps(struct amdgpu_dm_connector *aconnector)
>>          panel_backlight_quirk =
>>                  drm_get_panel_backlight_quirk(aconnector->drm_edid);
>>          if (!IS_ERR_OR_NULL(panel_backlight_quirk)) {
>> -               if (panel_backlight_quirk->min_brightness)
>> +               if (panel_backlight_quirk->min_brightness) {
>> +                       drm_info(drm,
>> +                                "Applying panel backlight quirk, min_brightness: %d\n",
>> +                                panel_backlight_quirk->min_brightness);
> 
> mmm, needs a -1 here
> 

You may as well re-order it too so that you set caps->min_input_signal 
and access it in this message.

>>                          caps->min_input_signal =
>>                                  panel_backlight_quirk->min_brightness - 1;
>> -               if (panel_backlight_quirk->brightness_mask)
>> +               }
>> +               if (panel_backlight_quirk->brightness_mask) {
>> +                       drm_info(drm,
>> +                                "Applying panel backlight quirk, brightness_mask: 0x%X\n",
>> +                                panel_backlight_quirk->brightness_mask);
>>                          caps->brightness_mask =
>>                                  panel_backlight_quirk->brightness_mask;
>> +               }
>>          }
>>   }
>>
>> --
>> 2.51.0
>>
>>
>