[PATCH weston v11 11/13] compositor-drm: Don't repaint if no damage

[Pekka Paalanen]

On Tue, 18 Jul 2017 14:14:33 +0100
Daniel Stone <daniels at collabora.com> wrote:

> If we don't have any damage for the primary plane, then don't force a
> repaint; simply reuse the old buffer we already have.
> 
> Signed-off-by: Daniel Stone <daniels at collabora.com>
> ---
>  libweston/compositor-drm.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/libweston/compositor-drm.c b/libweston/compositor-drm.c
> index bf3273ba..ca4146a5 100644
> --- a/libweston/compositor-drm.c
> +++ b/libweston/compositor-drm.c
> @@ -1507,6 +1507,7 @@ drm_output_render(struct drm_output_state *state, pixman_region32_t *damage)
>  	struct drm_output *output = state->output;
>  	struct weston_compositor *c = output->base.compositor;
>  	struct drm_plane_state *scanout_state;
> +	struct drm_plane *scanout_plane = output->scanout_plane;
>  	struct drm_backend *b = to_drm_backend(c);
>  	struct drm_fb *fb;
>  
> @@ -1517,10 +1518,20 @@ drm_output_render(struct drm_output_state *state, pixman_region32_t *damage)
>  	if (scanout_state->fb)
>  		return;
>  
> -	if (b->use_pixman)
> +	if (!pixman_region32_not_empty(damage) &&
> +	    scanout_plane->state_cur->fb &&
> +	    (scanout_plane->state_cur->fb->type == BUFFER_GBM_SURFACE ||
> +	     scanout_plane->state_cur->fb->type == BUFFER_PIXMAN_DUMB) &&
> +	    scanout_plane->state_cur->fb->width ==
> +		output->base.current_mode->width &&
> +	    scanout_plane->state_cur->fb->height ==
> +		output->base.current_mode->height) {
> +		fb = drm_fb_ref(scanout_plane->state_cur->fb);
> +	} else if (b->use_pixman) {
>  		fb = drm_output_render_pixman(state, damage);
> -	else
> +	} else {
>  		fb = drm_output_render_gl(state, damage);
> +	}
>  
>  	if (!fb) {
>  		drm_plane_state_put_back(scanout_state);

Hi,

is there a reason to check the buffer type at all? You want to be sure
the previous buffer came from the renderer? But if there is no damage
and state_cur has a BUFFER_CLIENT, is there any harm in re-using that?
OTOH, if there is no damage, one would assume the BUFFER_CLIENT would
have been kept promoted to scanout...

Shrug? :-)

Reviewed-by: Pekka Paalanen <pekka.paalanen at collabora.co.uk>


Thanks,
pq
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