diff options
Diffstat (limited to 'drivers/gpu/drm/drm_plane.c')
| -rw-r--r-- | drivers/gpu/drm/drm_plane.c | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c index f3f2eae83cca..9e8e4c60983d 100644 --- a/drivers/gpu/drm/drm_plane.c +++ b/drivers/gpu/drm/drm_plane.c @@ -1558,6 +1558,36 @@ out: * Drivers implementing damage can use drm_atomic_helper_damage_iter_init() and * drm_atomic_helper_damage_iter_next() helper iterator function to get damage * rectangles clipped to &drm_plane_state.src. + * + * Note that there are two types of damage handling: frame damage and buffer + * damage, the type of damage handling implemented depends on a driver's upload + * target. Drivers implementing a per-plane or per-CRTC upload target need to + * handle frame damage, while drivers implementing a per-buffer upload target + * need to handle buffer damage. + * + * The existing damage helpers only support the frame damage type, there is no + * buffer age support or similar damage accumulation algorithm implemented yet. + * + * Only drivers handling frame damage can use the mentioned damage helpers to + * iterate over the damaged regions. Drivers that handle buffer damage, must set + * &drm_plane_state.ignore_damage_clips for drm_atomic_helper_damage_iter_init() + * to know that damage clips should be ignored and return &drm_plane_state.src + * as the damage rectangle, to force a full plane update. + * + * Drivers with a per-buffer upload target could compare the &drm_plane_state.fb + * of the old and new plane states to determine if the framebuffer attached to a + * plane has changed or not since the last plane update. If &drm_plane_state.fb + * has changed, then &drm_plane_state.ignore_damage_clips must be set to true. + * + * That is because drivers with a per-plane upload target, expect the backing + * storage buffer to not change for a given plane. If the upload buffer changes + * between page flips, the new upload buffer has to be updated as a whole. This + * can be improved in the future if support for frame damage is added to the DRM + * damage helpers, similarly to how user-space already handle this case as it is + * explained in the following documents: + * + * https://registry.khronos.org/EGL/extensions/KHR/EGL_KHR_swap_buffers_with_damage.txt + * https://emersion.fr/blog/2019/intro-to-damage-tracking/ */ /** |