[PATCH 2/3] drm/i915/fbc: Don't nuke manually around flips

[Ville Syrjala]

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

Apparently we have discovered another way to hit the dreaded
top of screen FBC corruption on GLK. Previously we thought it
was limited to some combination of FBC nuke+disable+plane update
during the same frame, for which we have the extra vblank wait
as a workaround. But looks like it can somehow be hit even
without the FBC disable.

Skipping the extra manual nuke immediately after page flips seems
to cure this. The manual nuke shouldn't be needed anyway since the
flip itself will already cause a nuke. I suppose this means it might
still be possible to hit this if you mix page flips and frontbuffer
rendering in clever ways, but at least it's a bit less likely now.
---
 drivers/gpu/drm/i915/display/intel_fbc.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_fbc.c b/drivers/gpu/drm/i915/display/intel_fbc.c
index 1847a161cb37..a65239c1c25f 100644
--- a/drivers/gpu/drm/i915/display/intel_fbc.c
+++ b/drivers/gpu/drm/i915/display/intel_fbc.c
@@ -233,7 +233,8 @@ static void intel_fbc_recompress(struct drm_i915_private *dev_priv)
 
 static void ilk_fbc_activate(struct drm_i915_private *dev_priv)
 {
-	struct intel_fbc_reg_params *params = &dev_priv->fbc.params;
+	struct intel_fbc *fbc = &dev_priv->fbc;
+	struct intel_fbc_reg_params *params = &fbc->params;
 	u32 dpfc_ctl;
 	int threshold = dev_priv->fbc.threshold;
 
@@ -276,7 +277,8 @@ static void ilk_fbc_activate(struct drm_i915_private *dev_priv)
 	/* enable it... */
 	intel_de_write(dev_priv, ILK_DPFC_CONTROL, dpfc_ctl | DPFC_CTL_EN);
 
-	intel_fbc_recompress(dev_priv);
+	if (!fbc->active)
+		intel_fbc_recompress(dev_priv);
 }
 
 static void ilk_fbc_deactivate(struct drm_i915_private *dev_priv)
@@ -298,7 +300,8 @@ static bool ilk_fbc_is_active(struct drm_i915_private *dev_priv)
 
 static void gen7_fbc_activate(struct drm_i915_private *dev_priv)
 {
-	struct intel_fbc_reg_params *params = &dev_priv->fbc.params;
+	struct intel_fbc *fbc = &dev_priv->fbc;
+	struct intel_fbc_reg_params *params = &fbc->params;
 	u32 dpfc_ctl;
 	int threshold = dev_priv->fbc.threshold;
 
@@ -350,7 +353,8 @@ static void gen7_fbc_activate(struct drm_i915_private *dev_priv)
 
 	intel_de_write(dev_priv, ILK_DPFC_CONTROL, dpfc_ctl | DPFC_CTL_EN);
 
-	intel_fbc_recompress(dev_priv);
+	if (!fbc->active)
+		intel_fbc_recompress(dev_priv);
 }
 
 static bool intel_fbc_hw_is_active(struct drm_i915_private *dev_priv)
@@ -369,9 +373,6 @@ static void intel_fbc_hw_activate(struct drm_i915_private *dev_priv)
 
 	trace_intel_fbc_activate(fbc->crtc);
 
-	fbc->active = true;
-	fbc->activated = true;
-
 	if (DISPLAY_VER(dev_priv) >= 7)
 		gen7_fbc_activate(dev_priv);
 	else if (DISPLAY_VER(dev_priv) >= 5)
@@ -380,6 +381,9 @@ static void intel_fbc_hw_activate(struct drm_i915_private *dev_priv)
 		g4x_fbc_activate(dev_priv);
 	else
 		i8xx_fbc_activate(dev_priv);
+
+	fbc->active = true;
+	fbc->activated = true;
 }
 
 static void intel_fbc_hw_deactivate(struct drm_i915_private *dev_priv)
-- 
2.26.3