Re: [PATCH 5/7] drm/amd/display: Reset plane for anything that's not a FAST update

["Kazlauskas, Nicholas" <nicholas.kazlauskas@amd.com>]

On 2020-08-05 4:45 p.m., Rodrigo Siqueira wrote:
> On 07/30, Nicholas Kazlauskas wrote:
>> [Why]
>> MEDIUM or FULL updates can require global validation or affect
>> bandwidth. By treating these all simply as surface updates we aren't
>> actually passing this through DC global validation.
>>
>> [How]
>> There's currently no way to pass surface updates through DC global
>> validation, nor do I think it's a good idea to change the interface
>> to accept these.
>>
>> DC global validation itself is currently stateless, and we can move
>> our update type checking to be stateless as well by duplicating DC
>> surface checks in DM based on DRM properties.
>>
>> We wanted to rely on DC automatically determining this since DC knows
>> best, but DM is ultimately what fills in everything into DC plane
>> state so it does need to know as well.
>>
>> There are basically only three paths that we exercise in DM today:
>>
>> 1) Cursor (async update)
>> 2) Pageflip (fast update)
>> 3) Full pipe programming (medium/full updates)
>>
>> Which means that anything that's more than a pageflip really needs to
>> go down path #3.
>>
>> So this change duplicates all the surface update checks based on DRM
>> state instead inside of should_reset_plane().
>>
>> Next step is dropping dm_determine_update_type_for_commit and we no
>> longer require the old DC state at all for global validation.
>>
>> Optimization can come later so we don't reset DC planes at all for
>> MEDIUM udpates and avoid validation, but we might require some extra
>> checks in DM to achieve this.
> 
> How about adding this optimization description in our TODO list
> under-display folder?
> 
> Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>

Sure, I'll make another patch to clean up some of the TODO items in the 
text file.

Regards,
Nicholas Kazlauskas

>   
>> Cc: Bhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
>> Cc: Hersen Wu <hersenxs.wu@amd.com>
>> Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
>> ---
>>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 25 +++++++++++++++++++
>>   1 file changed, 25 insertions(+)
>>
>> 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 0d5f45742bb5..2cbb29199e61 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> @@ -8336,6 +8336,31 @@ static bool should_reset_plane(struct drm_atomic_state *state,
>>   		if (old_other_state->crtc != new_other_state->crtc)
>>   			return true;
>>   
>> +		/* Src/dst size and scaling updates. */
>> +		if (old_other_state->src_w != new_other_state->src_w ||
>> +		    old_other_state->src_h != new_other_state->src_h ||
>> +		    old_other_state->crtc_w != new_other_state->crtc_w ||
>> +		    old_other_state->crtc_h != new_other_state->crtc_h)
>> +			return true;
>> +
>> +		/* Rotation / mirroring updates. */
>> +		if (old_other_state->rotation != new_other_state->rotation)
>> +			return true;
>> +
>> +		/* Blending updates. */
>> +		if (old_other_state->pixel_blend_mode !=
>> +		    new_other_state->pixel_blend_mode)
>> +			return true;
>> +
>> +		/* Alpha updates. */
>> +		if (old_other_state->alpha != new_other_state->alpha)
>> +			return true;
>> +
>> +		/* Colorspace changes. */
>> +		if (old_other_state->color_range != new_other_state->color_range ||
>> +		    old_other_state->color_encoding != new_other_state->color_encoding)
>> +			return true;
>> +
>>   		/* Framebuffer checks fall at the end. */
>>   		if (!old_other_state->fb || !new_other_state->fb)
>>   			continue;
>> -- 
>> 2.25.1
>>
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