From 27e78a2a1f92e79707b4fb18cff1276088ef9178 Mon Sep 17 00:00:00 2001
From: Daniel Vetter <daniel.vetter@ffwll.ch>
Date: Thu, 18 Jun 2015 10:30:21 +0200
Subject: [PATCH] drm/i915: Filter out no-op frontbuffer tracking flushes

Paulo noticed that the fbc frontbuffer tracking flush callback
occasionally gets a call without any bit set. This can happen when we
have to filter flush calls due to e.g. gpu rendering. Filter these
out.

Reported-by: Paulo Zanoni <przanoni@gmail.com>
Cc: Paulo Zanoni <przanoni@gmail.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/i915/intel_frontbuffer.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_frontbuffer.c b/drivers/gpu/drm/i915/intel_frontbuffer.c
index 3b0ac73ede8f..6a70a51332e9 100644
--- a/drivers/gpu/drm/i915/intel_frontbuffer.c
+++ b/drivers/gpu/drm/i915/intel_frontbuffer.c
@@ -175,6 +175,9 @@ void intel_frontbuffer_flush(struct drm_device *dev,
 	frontbuffer_bits &= ~dev_priv->fb_tracking.busy_bits;
 	mutex_unlock(&dev_priv->fb_tracking.lock);
 
+	if (!frontbuffer_bits)
+		return;
+
 	intel_mark_fb_busy(dev, frontbuffer_bits);
 
 	intel_edp_drrs_flush(dev, frontbuffer_bits);
-- 
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