drm/msm: Avoid dirtyfb stalls on video mode displays (v2)

Someone on IRC once asked an innocent enough sounding question:  Why
with xf86-video-modesetting is es2gears limited at 120fps.

So I broke out the perfetto tracing mesa MR and took a look.  It turns
out the problem was drm_atomic_helper_dirtyfb(), which would end up
waiting for vblank.. es2gears would rapidly push two frames to Xorg,
which would blit them to screen and in idle hook (I assume) call the
DIRTYFB ioctl.  Which in turn would do an atomic update to flush the
dirty rects, which would stall until the next vblank.  And then the
whole process would repeat.

But this is a bit silly, we only need dirtyfb for command mode DSI
panels.  So track in plane state whether dirtyfb is required, and
track in the fb how many attached planes require dirtyfb so that we
can skip it when not required.  (Note, mdp4 does not actually have
cmd mode support.)

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20220223191118.881321-1-robdclark@gmail.com
Signed-off-by: Rob Clark <robdclark@chromium.org>

1 files changed, 2 insertions, 4 deletions

diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
index 57b0cd6f917e..9f68aa685ed7 100644
--- a/drivers/gpu/drm/msm/msm_drv.h
+++ b/drivers/gpu/drm/msm/msm_drv.h
@@ -239,8 +239,6 @@ struct msm_format {
 
 struct msm_pending_timer;
 
-int msm_atomic_prepare_fb(struct drm_plane *plane,
-			  struct drm_plane_state *new_state);
 int msm_atomic_init_pending_timer(struct msm_pending_timer *timer,
 		struct msm_kms *kms, int crtc_idx);
 void msm_atomic_destroy_pending_timer(struct msm_pending_timer *timer);
@@ -299,9 +297,9 @@ int msm_gem_prime_pin(struct drm_gem_object *obj);
 void msm_gem_prime_unpin(struct drm_gem_object *obj);
 
 int msm_framebuffer_prepare(struct drm_framebuffer *fb,
-		struct msm_gem_address_space *aspace);
+		struct msm_gem_address_space *aspace, bool needs_dirtyfb);
 void msm_framebuffer_cleanup(struct drm_framebuffer *fb,
-		struct msm_gem_address_space *aspace);
+		struct msm_gem_address_space *aspace, bool needed_dirtyfb);
 uint32_t msm_framebuffer_iova(struct drm_framebuffer *fb,
 		struct msm_gem_address_space *aspace, int plane);
 struct drm_gem_object *msm_framebuffer_bo(struct drm_framebuffer *fb, int plane);