drm/imx: add deferred plane disabling

The DP (display processor) channel disable code tried to busy wait for
the DP sync flow end interrupt status bit when disabling the partial
plane without a full modeset. That never worked reliably, and it was
disabled completely by the recent "gpu: ipu-v3: remove IRQ dance on DC
channel disable" patch, causing ipu_wait_interrupt to always time out
after 50 ms, which in turn would trigger a timeout in
drm_atomic_helper_wait_for_vblanks.

This patch changes ipu_plane_atomic_disable to only queue a DP channel
register update at the next frame boundary and set a flag, which can be
done without any waiting whatsoever. The imx_drm_atomic_commit_tail then
calls a new ipu_plane_disable_deferred function that does the actual
IDMAC teardown of the planes that are flagged for deferred disabling,
after waiting for the vblank.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>

1 files changed, 18 insertions, 0 deletions

diff --git a/drivers/gpu/drm/imx/imx-drm-core.c b/drivers/gpu/drm/imx/imx-drm-core.c
index 2566e4dbe92e..cd3c2013ea70 100644
--- a/drivers/gpu/drm/imx/imx-drm-core.c
+++ b/drivers/gpu/drm/imx/imx-drm-core.c
@@ -30,6 +30,7 @@
 #include <video/imx-ipu-v3.h>
 
 #include "imx-drm.h"
+#include "ipuv3-plane.h"
 
 #define MAX_CRTC	4
 
@@ -122,6 +123,10 @@ static const struct drm_mode_config_funcs imx_drm_mode_config_funcs = {
 static void imx_drm_atomic_commit_tail(struct drm_atomic_state *state)
 {
 	struct drm_device *dev = state->dev;
+	struct drm_plane *plane;
+	struct drm_plane_state *old_plane_state;
+	bool plane_disabling = false;
+	int i;
 
 	drm_atomic_helper_commit_modeset_disables(dev, state);
 
@@ -131,6 +136,19 @@ static void imx_drm_atomic_commit_tail(struct drm_atomic_state *state)
 
 	drm_atomic_helper_commit_modeset_enables(dev, state);
 
+	for_each_plane_in_state(state, plane, old_plane_state, i) {
+		if (drm_atomic_plane_disabling(old_plane_state, plane->state))
+			plane_disabling = true;
+	}
+
+	if (plane_disabling) {
+		drm_atomic_helper_wait_for_vblanks(dev, state);
+
+		for_each_plane_in_state(state, plane, old_plane_state, i)
+			ipu_plane_disable_deferred(plane);
+
+	}
+
 	drm_atomic_helper_commit_hw_done(state);
 }