Re: [PATCH] drm/gud: Merge damage clips in full update mode

[Thomas Zimmermann]

Hi

Am 08.09.26 um 01:08 schrieb Sophie D:
> When running in full update mode, previously small updates (such as
> moving the mouse across the screen) would cause many full frames to be
> generated. This would bog down the bus and lower the effective framerate
> significantly - I was seeing a drop from 60 FPS to 2 FPS.
>
> This patch fixes the bug by merging damage clips together.
>
> Fixes: 73cfd166e045 ("drm/gud: Replace simple display pipe with DRM atomic helpers")
> Cc: <stable@xxxxxxxxxxxxxxx> # 6.18.x
> Signed-off-by: Sophie D <patches@xxxxxxxxx>
> ---
>   drivers/gpu/drm/gud/gud_pipe.c | 11 ++++++++---
>   1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/gud/gud_pipe.c b/drivers/gpu/drm/gud/gud_pipe.c
> index 5ef887d84..20418bf81 100644
> --- a/drivers/gpu/drm/gud/gud_pipe.c
> +++ b/drivers/gpu/drm/gud/gud_pipe.c
> @@ -647,9 +647,14 @@ void gud_plane_atomic_update(struct drm_plane *plane,
>   	if (ret)
>   		goto out;
>   
> -	drm_atomic_helper_damage_iter_init(&iter, old_state, new_state);
> -	drm_atomic_for_each_plane_damage(&iter, &damage)
> -		gud_fb_handle_damage(gdrm, fb, &shadow_plane_state->data[0], &damage);
> +	if (gdrm->flags & GUD_DISPLAY_FLAG_FULL_UPDATE) {
> +		if (drm_atomic_helper_damage_merged(old_state, new_state, &damage))
> +			gud_fb_handle_damage(gdrm, fb, &shadow_plane_state->data[0], &damage);
> +	} else {
> +		drm_atomic_helper_damage_iter_init(&iter, old_state, new_state);
> +		drm_atomic_for_each_plane_damage(&iter, &damage)
> +			gud_fb_handle_damage(gdrm, fb, &shadow_plane_state->data[0], &damage);
> +	}

Such state needs to be checked much earlier. Please set 
plane_state->ignore_damage_clips [1] at the end of 
gud_plane_atomic_check [2] if in full-update mode.  The damage iterator 
will then do the right thing.

[1] 
https://elixir.bootlin.com/linux/v7.2.2/source/include/drm/drm_plane.h#L207
[2] 
https://elixir.bootlin.com/linux/v7.2.2/source/drivers/gpu/drm/gud/gud_pipe.c#L569

Best regards
Thomas

>   
>   	drm_gem_fb_end_cpu_access(fb, DMA_FROM_DEVICE);
>   

--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, (HRB 36809, AG Nürnberg)