Re: [PATCH 2/6] drm: Add drm_atomic_helper_buffer_damage_{iter_init, merged}() helpers

[Thomas Zimmermann <tzimmermann@suse.de>]

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Hi

Am 09.11.23 um 18:24 schrieb Javier Martinez Canillas:
> To be used by drivers that do per-buffer (e.g: virtio-gpu) uploads (rather
> than per-plane uploads), since these type of drivers need to handle buffer
> damages instead of frame damages.
> 
> The drm_atomic_helper_buffer_damage_iter_init() has the same logic than
> drm_atomic_helper_damage_iter_init() but it also takes into account if the
> framebuffer attached to plane's state has changed since the last update.
> 
> And the drm_atomic_helper_buffer_damage_merged() is just a version of the
> drm_atomic_helper_damage_merged() helper, but it uses the iter_init helper
> that is mentioned above.
> 
> Fixes: 01f05940a9a7 ("drm/virtio: Enable fb damage clips property for the primary plane")
> Cc: <stable@vger.kernel.org> # v6.4+
> Reported-by: nerdopolis <bluescreen_avenger@verizon.net>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218115
> Suggested-by: Sima Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
> ---
> 
>   drivers/gpu/drm/drm_damage_helper.c | 79 ++++++++++++++++++++++++++---
>   include/drm/drm_damage_helper.h     |  7 +++
>   2 files changed, 80 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_damage_helper.c b/drivers/gpu/drm/drm_damage_helper.c
> index aa2325567918..b72062c9d31c 100644
> --- a/drivers/gpu/drm/drm_damage_helper.c
> +++ b/drivers/gpu/drm/drm_damage_helper.c
> @@ -204,7 +204,8 @@ EXPORT_SYMBOL(drm_atomic_helper_dirtyfb);
>   static void
>   __drm_atomic_helper_damage_iter_init(struct drm_atomic_helper_damage_iter *iter,
>   				     const struct drm_plane_state *old_state,
> -				     const struct drm_plane_state *state)
> +				     const struct drm_plane_state *state,
> +				     bool buffer_damage)
>   {
>   	struct drm_rect src;
>   	memset(iter, 0, sizeof(*iter));
> @@ -223,7 +224,8 @@ __drm_atomic_helper_damage_iter_init(struct drm_atomic_helper_damage_iter *iter,
>   	iter->plane_src.x2 = (src.x2 >> 16) + !!(src.x2 & 0xFFFF);
>   	iter->plane_src.y2 = (src.y2 >> 16) + !!(src.y2 & 0xFFFF);
>   
> -	if (!iter->clips || !drm_rect_equals(&state->src, &old_state->src)) {
> +	if (!iter->clips || !drm_rect_equals(&state->src, &old_state->src) ||
> +	    (buffer_damage && old_state->fb != state->fb)) {

I'd assume that this change effectivly disables damage handling. AFAICT 
user space often does a page flip with a new framebuffer plus damage 
data. Now, with each change of the framebuffer we ignore the damage 
information. It's not a blocker as that's the behavior before 6.4, but 
we should be aware of it.

Best regards
Thomas

>   		iter->clips = NULL;
>   		iter->num_clips = 0;
>   		iter->full_update = true;
> @@ -243,6 +245,10 @@ __drm_atomic_helper_damage_iter_init(struct drm_atomic_helper_damage_iter *iter,
>    * update). Currently this iterator returns full plane src in case plane src
>    * changed but that can be changed in future to return damage.
>    *
> + * Note that this helper is for drivers that do per-plane uploads and expect
> + * to handle frame damages. Drivers that do per-buffer uploads instead should
> + * use @drm_atomic_helper_buffer_damage_iter_init() that handles buffer damages.
> + *
>    * For the case when plane is not visible or plane update should not happen the
>    * first call to iter_next will return false. Note that this helper use clipped
>    * &drm_plane_state.src, so driver calling this helper should have called
> @@ -253,10 +259,37 @@ drm_atomic_helper_damage_iter_init(struct drm_atomic_helper_damage_iter *iter,
>   				   const struct drm_plane_state *old_state,
>   				   const struct drm_plane_state *state)
>   {
> -	__drm_atomic_helper_damage_iter_init(iter, old_state, state);
> +	__drm_atomic_helper_damage_iter_init(iter, old_state, state, false);
>   }
>   EXPORT_SYMBOL(drm_atomic_helper_damage_iter_init);
>   
> +/**
> + * drm_atomic_helper_buffer_damage_iter_init - Initialize the buffer damage iterator.
> + * @iter: The iterator to initialize.
> + * @old_state: Old plane state for validation.
> + * @state: Plane state from which to iterate the damage clips.
> + *
> + * Initialize an iterator, which clips buffer damage
> + * &drm_plane_state.fb_damage_clips to plane &drm_plane_state.src. This iterator
> + * returns full plane src in case buffer damage is not present because user-space
> + * didn't sent, driver discarded it (it want to do full plane update) or the plane
> + * @state has an attached framebuffer that is different than the one in @state (it
> + * has changed since the last plane update).
> + *
> + * For the case when plane is not visible or plane update should not happen the
> + * first call to iter_next will return false. Note that this helper use clipped
> + * &drm_plane_state.src, so driver calling this helper should have called
> + * drm_atomic_helper_check_plane_state() earlier.
> + */
> +void
> +drm_atomic_helper_buffer_damage_iter_init(struct drm_atomic_helper_damage_iter *iter,
> +					  const struct drm_plane_state *old_state,
> +					  const struct drm_plane_state *state)
> +{
> +	__drm_atomic_helper_damage_iter_init(iter, old_state, state, true);
> +}
> +EXPORT_SYMBOL(drm_atomic_helper_buffer_damage_iter_init);
> +
>   /**
>    * drm_atomic_helper_damage_iter_next - Advance the damage iterator.
>    * @iter: The iterator to advance.
> @@ -301,7 +334,8 @@ EXPORT_SYMBOL(drm_atomic_helper_damage_iter_next);
>   
>   static bool __drm_atomic_helper_damage_merged(const struct drm_plane_state *old_state,
>   					      struct drm_plane_state *state,
> -					      struct drm_rect *rect)
> +					      struct drm_rect *rect,
> +					      bool buffer_damage)
>   {
>   	struct drm_atomic_helper_damage_iter iter;
>   	struct drm_rect clip;
> @@ -312,7 +346,7 @@ static bool __drm_atomic_helper_damage_merged(const struct drm_plane_state *old_
>   	rect->x2 = 0;
>   	rect->y2 = 0;
>   
> -	drm_atomic_helper_damage_iter_init(&iter, old_state, state);
> +	__drm_atomic_helper_damage_iter_init(&iter, old_state, state, buffer_damage);
>   	drm_atomic_for_each_plane_damage(&iter, &clip) {
>   		rect->x1 = min(rect->x1, clip.x1);
>   		rect->y1 = min(rect->y1, clip.y1);
> @@ -336,6 +370,10 @@ static bool __drm_atomic_helper_damage_merged(const struct drm_plane_state *old_
>    * For details see: drm_atomic_helper_damage_iter_init() and
>    * drm_atomic_helper_damage_iter_next().
>    *
> + * Note that this helper is for drivers that do per-plane uploads and expect
> + * to handle frame damages. Drivers that do per-buffer uploads instead should
> + * use @drm_atomic_helper_buffer_damage_merged() that handles buffer damages.
> + *
>    * Returns:
>    * True if there is valid plane damage otherwise false.
>    */
> @@ -343,6 +381,35 @@ bool drm_atomic_helper_damage_merged(const struct drm_plane_state *old_state,
>   				     struct drm_plane_state *state,
>   				     struct drm_rect *rect)
>   {
> -	return __drm_atomic_helper_damage_merged(old_state, state, rect);
> +	return __drm_atomic_helper_damage_merged(old_state, state, rect, false);
>   }
>   EXPORT_SYMBOL(drm_atomic_helper_damage_merged);
> +
> +/**
> + * drm_atomic_helper_buffer_damage_merged - Merged buffer damage
> + * @old_state: Old plane state for validation.
> + * @state: Plane state from which to iterate the damage clips.
> + * @rect: Returns the merged buffer damage rectangle
> + *
> + * This function merges any valid buffer damage clips into one rectangle and
> + * returns it in @rect. It checks if the framebuffers attached to @old_state
> + * and @state are the same. If that is not the case then the returned damage
> + * rectangle is the &drm_plane_state.src, since a full update should happen.
> + *
> + * Note that &drm_plane_state.fb_damage_clips == NULL in plane state means that
> + * full plane update should happen. It also ensure helper iterator will return
> + * &drm_plane_state.src as damage.
> + *
> + * For details see: drm_atomic_helper_buffer_damage_iter_init() and
> + * drm_atomic_helper_damage_iter_next().
> + *
> + * Returns:
> + * True if there is valid buffer damage otherwise false.
> + */
> +bool drm_atomic_helper_buffer_damage_merged(const struct drm_plane_state *old_state,
> +					    struct drm_plane_state *state,
> +					    struct drm_rect *rect)
> +{
> +	return __drm_atomic_helper_damage_merged(old_state, state, rect, true);
> +}
> +EXPORT_SYMBOL(drm_atomic_helper_buffer_damage_merged);
> diff --git a/include/drm/drm_damage_helper.h b/include/drm/drm_damage_helper.h
> index effda42cce31..328bb249d68f 100644
> --- a/include/drm/drm_damage_helper.h
> +++ b/include/drm/drm_damage_helper.h
> @@ -74,11 +74,18 @@ void
>   drm_atomic_helper_damage_iter_init(struct drm_atomic_helper_damage_iter *iter,
>   				   const struct drm_plane_state *old_state,
>   				   const struct drm_plane_state *new_state);
> +void
> +drm_atomic_helper_buffer_damage_iter_init(struct drm_atomic_helper_damage_iter *iter,
> +					  const struct drm_plane_state *old_state,
> +					  const struct drm_plane_state *new_state);
>   bool
>   drm_atomic_helper_damage_iter_next(struct drm_atomic_helper_damage_iter *iter,
>   				   struct drm_rect *rect);
>   bool drm_atomic_helper_damage_merged(const struct drm_plane_state *old_state,
>   				     struct drm_plane_state *state,
>   				     struct drm_rect *rect);
> +bool drm_atomic_helper_buffer_damage_merged(const struct drm_plane_state *old_state,
> +					    struct drm_plane_state *state,
> +					    struct drm_rect *rect);
>   
>   #endif

-- 
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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