Re: [PATCH] drm/amd/display: Don't stretch non-native images by default in eDP

["Mario Limonciello (AMD) (kernel.org)" <superm1@kernel.org>]

On 10/30/2025 3:49 PM, Alex Deucher wrote:
> On Thu, Oct 30, 2025 at 4:16 PM Mario Limonciello (AMD)
> <superm1@kernel.org> wrote:
>>
>> commit 978fa2f6d0b12 ("drm/amd/display: Use scaling for non-native
>> resolutions on eDP") started using the GPU scaler hardware to scale
>> when a non-native resolution was picked on eDP. This scaling was done
>> to fill the screen instead of maintain aspect ratio.
>>
>> The idea was supposed to be that if a different scaling behavior is
>> preferred then the compositor would request it.  The not following
>> aspect ratio behavior however isn't desirable, so adjust it to follow
>> aspect ratio and still try to fill screen.
>>
>> Note: This will lead to black bars in some cases for non-native
>> resolutions. Compositors can request the previous behavior if desired.
>>
> 
> We may end up getting bug reports about the black bars.  We had a
> similar debate about what the right default was for radeon 15 years
> ago.  That said, at least with this the pixels will be square with
> this patch.
> 
> Acked-by: Alex Deucher <alexander.deucher@amd.com>

Thanks.  Yeah that was my thought too.

> 
>> Fixes: 978fa2f6d0b12 ("drm/amd/display: Use scaling for non-native resolutions on eDP")
>> Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4538
>> Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
>> ---
>>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> 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 29b9197bbbc32..5b279182e66a8 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> @@ -8078,7 +8078,7 @@ static int dm_encoder_helper_atomic_check(struct drm_encoder *encoder,
>>                                         "mode %dx%d@%dHz is not native, enabling scaling\n",
>>                                         adjusted_mode->hdisplay, adjusted_mode->vdisplay,
>>                                         drm_mode_vrefresh(adjusted_mode));
>> -                       dm_new_connector_state->scaling = RMX_FULL;
>> +                       dm_new_connector_state->scaling = RMX_ASPECT;
>>                  }
>>                  return 0;
>>          }
>> --
>> 2.43.0
>>