[Intel-gfx] [PATCH 03/14] drm/i915: improve GEN7_ERR_INT clearing for fifo underrun reporting

[Daniel Vetter]

Same treatment as for SERR_INT: If we clear only the bit for the pipe
we're enabling (but unconditionally) then we can always check for
possible underruns after having disabled the interrupt. That way pipe
underruns won't be lost, but at worst only get reported in a delayed
fashion.

v2: The same logic bug as in the SERR handling change also existed
here. The same bugfix of only reporting missed underruns when the
error interrupt was masked applies, too.

Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/i915/i915_irq.c | 17 +++++++++++------
 drivers/gpu/drm/i915/i915_reg.h |  1 +
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index bbf4df8..88e6e47 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -154,21 +154,26 @@ static void ironlake_set_fifo_underrun_reporting(struct drm_device *dev,
 }
 
 static void ivybridge_set_fifo_underrun_reporting(struct drm_device *dev,
-						  bool enable)
+						  enum pipe pipe, bool enable)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
+	bool was_enabled = !(I915_READ(DEIMR) & DE_ERR_INT_IVB);
 
 	if (enable) {
+		I915_WRITE(GEN7_ERR_INT, ERR_INT_FIFO_UNDERRUN(pipe));
+
 		if (!ivb_can_enable_err_int(dev))
 			return;
 
-		I915_WRITE(GEN7_ERR_INT, ERR_INT_FIFO_UNDERRUN_A |
-					 ERR_INT_FIFO_UNDERRUN_B |
-					 ERR_INT_FIFO_UNDERRUN_C);
-
 		ironlake_enable_display_irq(dev_priv, DE_ERR_INT_IVB);
 	} else {
 		ironlake_disable_display_irq(dev_priv, DE_ERR_INT_IVB);
+
+		if (!was_enabled &&
+		    (I915_READ(GEN7_ERR_INT) & ERR_INT_FIFO_UNDERRUN(pipe))) {
+			DRM_DEBUG_KMS("uncleared fifo underrun on pipe %i\n",
+				      pipe_name(pipe));
+		}
 	}
 }
 
@@ -273,7 +278,7 @@ bool intel_set_cpu_fifo_underrun_reporting(struct drm_device *dev,
 	if (IS_GEN5(dev) || IS_GEN6(dev))
 		ironlake_set_fifo_underrun_reporting(dev, pipe, enable);
 	else if (IS_GEN7(dev))
-		ivybridge_set_fifo_underrun_reporting(dev, enable);
+		ivybridge_set_fifo_underrun_reporting(dev, pipe, enable);
 
 done:
 	spin_unlock_irqrestore(&dev_priv->irq_lock, flags);
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 5bba39a..58ca1d0 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -681,6 +681,7 @@
 #define   ERR_INT_FIFO_UNDERRUN_C	(1<<6)
 #define   ERR_INT_FIFO_UNDERRUN_B	(1<<3)
 #define   ERR_INT_FIFO_UNDERRUN_A	(1<<0)
+#define   ERR_INT_FIFO_UNDERRUN(pipe)	(1<< (pipe*3))
 
 #define FPGA_DBG		0x42300
 #define   FPGA_DBG_RM_NOCLAIM	(1<<31)
-- 
1.8.1.4