Re: [PATCH v2 0/5] drm: Allow the damage helpers to handle buffer damage

[Thomas Zimmermann <tzimmermann@suse.de>]

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Hi Javier,

please take my

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>

for the whole patch set. Maybe consider my comment on patch 4.

Best regards
Thomas

Am 15.11.23 um 14:15 schrieb Javier Martinez Canillas:
> Hello,
> 
> This series is to fix an issue that surfaced after damage clipping was
> enabled for the virtio-gpu by commit 01f05940a9a7 ("drm/virtio: Enable
> fb damage clips property for the primary plane").
> 
> After that change, flickering artifacts was reported to be present with
> both weston and wlroots wayland compositors when running in a virtual
> machine. The cause was identified by Sima Vetter, who pointed out that
> virtio-gpu does per-buffer uploads and for this reason it needs to do
> a buffer damage handling, instead of frame damage handling.
> 
> Their suggestion was to extend the damage helpers to cover that case
> and given that there's isn't a buffer damage accumulation algorithm
> (e.g: buffer age), just do a full plane update if the framebuffer that
> is attached to a plane changed since the last plane update (page-flip).
> 
> It is a v2 that addresses issues pointed out by Thomas Zimmermann in v1:
> https://lists.freedesktop.org/archives/dri-devel/2023-November/430138.html
> 
> Patch #1 adds a ignore_damage_clips field to struct drm_plane_state to be
> set by drivers that want the damage helpers to ignore the damage clips.
> 
> Patch #2 fixes the virtio-gpu damage handling logic by asking the damage
> helper to ignore the damage clips if the framebuffer attached to a plane
> has changed since the last page-flip.
> 
> Patch #3 does the same but for the vmwgfx driver that also needs to handle
> buffer damage and should have the same issue (although I haven't tested it
> due not having a VMWare setup).
> 
> Patch #4 adds to the KMS damage tracking kernel-doc some paragraphs about
> damage tracking types and references to links that explain frame damage vs
> buffer damage.
> 
> Finally patch #5 adds an item to the DRM todo, about the need to implement
> some buffer damage accumulation algorithm instead of just doing full plane
> updates in this case.
> 
> Because commit 01f05940a9a7 landed in v6.4, the first 2 patches are marked
> as Fixes and Cc stable.
> 
> I've tested this on a VM with weston, was able to reproduce the issue
> reported and the patches did fix the problem.
> 
> Best regards,
> Javier
> 
> Changes in v2:
> - Add a struct drm_plane_state .ignore_damage_clips to set in the plane's
>    .atomic_check, instead of having different helpers (Thomas Zimmermann).
> - Set struct drm_plane_state .ignore_damage_clips in virtio-gpu plane's
>    .atomic_check instead of using a different helpers (Thomas Zimmermann).
> - Set struct drm_plane_state .ignore_damage_clips in vmwgfx plane's
>    .atomic_check instead of using a different helpers (Thomas Zimmermann).
> 
> Javier Martinez Canillas (5):
>    drm: Allow drivers to indicate the damage helpers to ignore damage
>      clips
>    drm/virtio: Disable damage clipping if FB changed since last page-flip
>    drm/vmwgfx: Disable damage clipping if FB changed since last page-flip
>    drm/plane: Extend damage tracking kernel-doc
>    drm/todo: Add entry about implementing buffer age for damage tracking
> 
>   Documentation/gpu/todo.rst             | 20 ++++++++++++++++++++
>   drivers/gpu/drm/drm_damage_helper.c    |  3 ++-
>   drivers/gpu/drm/drm_plane.c            | 20 ++++++++++++++++++++
>   drivers/gpu/drm/virtio/virtgpu_plane.c | 10 ++++++++++
>   drivers/gpu/drm/vmwgfx/vmwgfx_kms.c    | 11 +++++++++++
>   include/drm/drm_plane.h                |  8 ++++++++
>   6 files changed, 71 insertions(+), 1 deletion(-)
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

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