[Intel-gfx] [PATCH 4/5] drm/i915: Wait for pending page flips before enabling/disabling the primary plane

[ville.syrjala at linux.intel.com]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

We have to write to the primary plane base address registrer when we
enable/disable the primary plane in response to sprite coverage. Those
writes will cause the flip counter to increment which could interfere
with the detection of CS flip completion. We could end up completing
CS flips before the CS has even executed the commands from the ring.

To avoid such issues, wait for CS flips to finish before we toggle the
primary plane on/off.

Testcase: igt/kms_mmio_vs_cs_flip/setplane_vs_cs_flip
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_display.c | 2 +-
 drivers/gpu/drm/i915/intel_drv.h     | 1 +
 drivers/gpu/drm/i915/intel_sprite.c  | 4 ++++
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 9b181fc..c0fe5dd 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -3096,7 +3096,7 @@ bool intel_has_pending_fb_unpin(struct drm_device *dev)
 	return false;
 }
 
-static void intel_crtc_wait_for_pending_flips(struct drm_crtc *crtc)
+void intel_crtc_wait_for_pending_flips(struct drm_crtc *crtc)
 {
 	struct drm_device *dev = crtc->dev;
 	struct drm_i915_private *dev_priv = dev->dev_private;
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index edef34e..f578e42 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -775,6 +775,7 @@ int valleyview_get_vco(struct drm_i915_private *dev_priv);
 void intel_mode_from_pipe_config(struct drm_display_mode *mode,
 				 struct intel_crtc_config *pipe_config);
 int intel_format_to_fourcc(int format);
+void intel_crtc_wait_for_pending_flips(struct drm_crtc *crtc);
 
 /* intel_dp.c */
 void intel_dp_init(struct drm_device *dev, int output_reg, enum port port);
diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
index 4df7245..36a8f5e 100644
--- a/drivers/gpu/drm/i915/intel_sprite.c
+++ b/drivers/gpu/drm/i915/intel_sprite.c
@@ -529,6 +529,8 @@ intel_enable_primary(struct drm_crtc *crtc)
 	if (intel_crtc->primary_enabled)
 		return;
 
+	intel_crtc_wait_for_pending_flips(crtc);
+
 	intel_crtc->primary_enabled = true;
 
 	I915_WRITE(reg, I915_READ(reg) | DISPLAY_PLANE_ENABLE);
@@ -558,6 +560,8 @@ intel_disable_primary(struct drm_crtc *crtc)
 	if (!intel_crtc->primary_enabled)
 		return;
 
+	intel_crtc_wait_for_pending_flips(crtc);
+
 	intel_crtc->primary_enabled = false;
 
 	mutex_lock(&dev->struct_mutex);
-- 
1.8.3.2