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 <[e-mail]>
Reviewed-by: Lucas Stach <[e-mail]>

drivers/gpu/drm/imx/imx-drm-core.c

···
 #include <video/imx-ipu-v3.h>
 
 #include "imx-drm.h"
+#include "ipuv3-plane.h"
 
 #define MAX_CRTC	4
 
···
 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);
 
···
 				DRM_PLANE_COMMIT_NO_DISABLE_AFTER_MODESET);
 
 	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);
 }

drivers/gpu/drm/imx/ipuv3-crtc.c

···
 	ipu_di_enable(ipu_crtc->di);
 }
 
+static void ipu_crtc_disable_planes(struct ipu_crtc *ipu_crtc,
+				    struct drm_crtc_state *old_crtc_state)
+{
+	bool disable_partial = false;
+	bool disable_full = false;
+	struct drm_plane *plane;
+
+	drm_atomic_crtc_state_for_each_plane(plane, old_crtc_state) {
+		if (plane == &ipu_crtc->plane[0]->base)
+			disable_full = true;
+		if (&ipu_crtc->plane[1] && plane == &ipu_crtc->plane[1]->base)
+			disable_partial = true;
+	}
+
+	if (disable_partial)
+		ipu_plane_disable(ipu_crtc->plane[1], true);
+	if (disable_full)
+		ipu_plane_disable(ipu_crtc->plane[0], false);
+}
+
 static void ipu_crtc_atomic_disable(struct drm_crtc *crtc,
 				    struct drm_crtc_state *old_crtc_state)
 {
···
 	 * attached IDMACs will be left in undefined state, possibly hanging
 	 * the IPU or even system.
 	 */
-	drm_atomic_helper_disable_planes_on_crtc(old_crtc_state, false);
+	ipu_crtc_disable_planes(ipu_crtc, old_crtc_state);
 	ipu_dc_disable(ipu);
 
 	spin_lock_irq(&crtc->dev->event_lock);

drivers/gpu/drm/imx/ipuv3-plane.c

···
 		ipu_dp_enable_channel(ipu_plane->dp);
 }
 
-static int ipu_disable_plane(struct drm_plane *plane)
+void ipu_plane_disable(struct ipu_plane *ipu_plane, bool disable_dp_channel)
 {
-	struct ipu_plane *ipu_plane = to_ipu_plane(plane);
-
 	DRM_DEBUG_KMS("[%d] %s\n", __LINE__, __func__);
 
 	ipu_idmac_wait_busy(ipu_plane->ipu_ch, 50);
 
-	if (ipu_plane->dp)
-		ipu_dp_disable_channel(ipu_plane->dp, true);
+	if (ipu_plane->dp && disable_dp_channel)
+		ipu_dp_disable_channel(ipu_plane->dp, false);
 	ipu_idmac_disable_channel(ipu_plane->ipu_ch);
 	ipu_dmfc_disable_channel(ipu_plane->dmfc);
 	if (ipu_plane->dp)
 		ipu_dp_disable(ipu_plane->ipu);
-
-	return 0;
 }
+
+void ipu_plane_disable_deferred(struct drm_plane *plane)
+{
+	struct ipu_plane *ipu_plane = to_ipu_plane(plane);
+
+	if (ipu_plane->disabling) {
+		ipu_plane->disabling = false;
+		ipu_plane_disable(ipu_plane, false);
+	}
+}
+EXPORT_SYMBOL_GPL(ipu_plane_disable_deferred);
 
 static void ipu_plane_destroy(struct drm_plane *plane)
 {
···
 static void ipu_plane_atomic_disable(struct drm_plane *plane,
 				     struct drm_plane_state *old_state)
 {
-	ipu_disable_plane(plane);
+	struct ipu_plane *ipu_plane = to_ipu_plane(plane);
+
+	if (ipu_plane->dp)
+		ipu_dp_disable_channel(ipu_plane->dp, true);
+	ipu_plane->disabling = true;
 }
 
 static void ipu_plane_atomic_update(struct drm_plane *plane,

drivers/gpu/drm/imx/ipuv3-plane.h

···
 
 	int			dma;
 	int			dp_flow;
+
+	bool			disabling;
 };
 
 struct ipu_plane *ipu_plane_init(struct drm_device *dev, struct ipu_soc *ipu,
···
 void ipu_plane_put_resources(struct ipu_plane *plane);
 
 int ipu_plane_irq(struct ipu_plane *plane);
+
+void ipu_plane_disable(struct ipu_plane *ipu_plane, bool disable_dp_channel);
+void ipu_plane_disable_deferred(struct drm_plane *plane);
 
 #endif

drivers/gpu/ipu-v3/ipu-dp.c

···
 	writel(0, flow->base + DP_FG_POS);
 	ipu_srm_dp_update(priv->ipu, sync);
 
-	if (ipu_idmac_channel_busy(priv->ipu, IPUV3_CHANNEL_MEM_BG_SYNC))
-		ipu_wait_interrupt(priv->ipu, IPU_IRQ_DP_SF_END, 50);
-
 	mutex_unlock(&priv->mutex);
 }
 EXPORT_SYMBOL_GPL(ipu_dp_disable_channel);