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>
 
> 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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-- 
Rodrigo Siqueira
https://siqueira.tech