[Intel-gfx] [PATCH 1/2] 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 be hit even if the plane
update happens during a different frame.

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.

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 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 91dad8004c34..4fc3633eb614 100644
--- a/drivers/gpu/drm/i915/display/intel_fbc.c
+++ b/drivers/gpu/drm/i915/display/intel_fbc.c
@@ -232,7 +232,8 @@ 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;
 
@@ -275,7 +276,8 @@ 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)
@@ -297,7 +299,8 @@ 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;
 
@@ -349,7 +352,8 @@ 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)
@@ -368,9 +372,6 @@ 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)
@@ -379,6 +380,9 @@ 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