[Intel-gfx] [PATCH 1/5] drm/i915: Check for FIFO underuns when disabling reporting on gmch platforms

[ville.syrjala at linux.intel.com]

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

FIFO underruns don't generate an interrupt on gmch platforms, so we
should check whether there were any that we failed to notice when
we're disabling FIFO underrun reporting.

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/i915_irq.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index b10fbde..8bb564b 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -266,16 +266,22 @@ static bool cpt_can_enable_serr_int(struct drm_device *dev)
 	return true;
 }
 
-static void i9xx_clear_fifo_underrun(struct drm_device *dev, enum pipe pipe)
+static void i9xx_set_fifo_underrun_reporting(struct drm_device *dev,
+					     enum pipe pipe, bool enable)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	u32 reg = PIPESTAT(pipe);
-	u32 pipestat = I915_READ(reg) & 0x7fff0000;
+	u32 pipestat = I915_READ(reg) & 0xffff0000;
 
 	assert_spin_locked(&dev_priv->irq_lock);
 
-	I915_WRITE(reg, pipestat | PIPE_FIFO_UNDERRUN_STATUS);
-	POSTING_READ(reg);
+	if (enable) {
+		I915_WRITE(reg, pipestat | PIPE_FIFO_UNDERRUN_STATUS);
+		POSTING_READ(reg);
+	} else {
+		if (pipestat & PIPE_FIFO_UNDERRUN_STATUS)
+			DRM_ERROR("pipe %c underrun\n", pipe_name(pipe));
+	}
 }
 
 static void ironlake_set_fifo_underrun_reporting(struct drm_device *dev,
@@ -432,8 +438,8 @@ bool __intel_set_cpu_fifo_underrun_reporting(struct drm_device *dev,
 
 	intel_crtc->cpu_fifo_underrun_disabled = !enable;
 
-	if (enable && (INTEL_INFO(dev)->gen < 5 || IS_VALLEYVIEW(dev)))
-		i9xx_clear_fifo_underrun(dev, pipe);
+	if (INTEL_INFO(dev)->gen < 5 || IS_VALLEYVIEW(dev))
+		i9xx_set_fifo_underrun_reporting(dev, pipe, enable);
 	else if (IS_GEN5(dev) || IS_GEN6(dev))
 		ironlake_set_fifo_underrun_reporting(dev, pipe, enable);
 	else if (IS_GEN7(dev))
-- 
1.8.5.5