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, 17 insertions, 2 deletions

diff --git a/drivers/gpu/drm/msm/disp/mdp4/mdp4_plane.c b/drivers/gpu/drm/msm/disp/mdp4/mdp4_plane.c
index 49bdabea8ed5..3e20f72d75ef 100644
--- a/drivers/gpu/drm/msm/disp/mdp4/mdp4_plane.c
+++ b/drivers/gpu/drm/msm/disp/mdp4/mdp4_plane.c
@@ -7,6 +7,7 @@
 #include <drm/drm_atomic.h>
 #include <drm/drm_damage_helper.h>
 #include <drm/drm_fourcc.h>
+#include <drm/drm_gem_atomic_helper.h>
 
 #include "mdp4_kms.h"
 
@@ -90,6 +91,20 @@ static const struct drm_plane_funcs mdp4_plane_funcs = {
 		.atomic_destroy_state = drm_atomic_helper_plane_destroy_state,
 };
 
+static int mdp4_plane_prepare_fb(struct drm_plane *plane,
+				 struct drm_plane_state *new_state)
+{
+	struct msm_drm_private *priv = plane->dev->dev_private;
+	struct msm_kms *kms = priv->kms;
+
+	if (!new_state->fb)
+		return 0;
+
+	drm_gem_plane_helper_prepare_fb(plane, new_state);
+
+	return msm_framebuffer_prepare(new_state->fb, kms->aspace, false);
+}
+
 static void mdp4_plane_cleanup_fb(struct drm_plane *plane,
 				  struct drm_plane_state *old_state)
 {
@@ -102,7 +117,7 @@ static void mdp4_plane_cleanup_fb(struct drm_plane *plane,
 		return;
 
 	DBG("%s: cleanup: FB[%u]", mdp4_plane->name, fb->base.id);
-	msm_framebuffer_cleanup(fb, kms->aspace);
+	msm_framebuffer_cleanup(fb, kms->aspace, false);
 }
 
 
@@ -130,7 +145,7 @@ static void mdp4_plane_atomic_update(struct drm_plane *plane,
 }
 
 static const struct drm_plane_helper_funcs mdp4_plane_helper_funcs = {
-		.prepare_fb = msm_atomic_prepare_fb,
+		.prepare_fb = mdp4_plane_prepare_fb,
 		.cleanup_fb = mdp4_plane_cleanup_fb,
 		.atomic_check = mdp4_plane_atomic_check,
 		.atomic_update = mdp4_plane_atomic_update,