[Intel-gfx] [PATCH 2/2] 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 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.

v2: Rebase

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/display/intel_fbc.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_fbc.c b/drivers/gpu/drm/i915/display/intel_fbc.c
index ef2f1ece4a89..d909402bd151 100644
--- a/drivers/gpu/drm/i915/display/intel_fbc.c
+++ b/drivers/gpu/drm/i915/display/intel_fbc.c
@@ -458,11 +458,13 @@ static void intel_fbc_activate(struct drm_i915_private *dev_priv)
 
 	trace_intel_fbc_activate(fbc->crtc);
 
+	intel_fbc_hw_activate(dev_priv);
+
+	if (!fbc->active)
+		intel_fbc_recompress(dev_priv);
+
 	fbc->active = true;
 	fbc->activated = true;
-
-	intel_fbc_hw_activate(dev_priv);
-	intel_fbc_recompress(dev_priv);
 }
 
 static void intel_fbc_deactivate(struct drm_i915_private *dev_priv,
-- 
2.32.0