[PATCH 7/7] drm/i915: print Gen 7 error interrupts

[Paulo Zanoni <przanoni@gmail.com>]

From: Paulo Zanoni <paulo.r.zanoni@intel.com>

If we get one of these messages it means we did something wrong, and
the first step to fix wrong things is to detect them and recognize
they exist.

For now, leave most messages as DRM_DEBUG_KMS. After we conclude that
a certain message should not be print since our code is correct, then
we can promote that specific message to DRM_ERROR.

Also notice that on Haswell the only interrupt I ever get is for
"unclaimed registers", so it looks like at least on Haswell we're in a
good shape.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
---
 drivers/gpu/drm/i915/i915_irq.c |   28 +++++++++++++++++++++++++++-
 drivers/gpu/drm/i915/i915_reg.h |    2 +-
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 943db10..c2136cd 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -697,6 +697,17 @@ static void cpt_irq_handler(struct drm_device *dev, u32 pch_iir)
 					 I915_READ(FDI_RX_IIR(pipe)));
 }
 
+static void ivb_err_int_handler(struct drm_device *dev)
+{
+	drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
+	u32 err_int = I915_READ(GEN7_ERR_INT);
+
+	if (err_int)
+		DRM_DEBUG_KMS("Error interrupt: 0x%08x\n", err_int);
+
+	I915_WRITE(GEN7_ERR_INT, err_int);
+}
+
 static irqreturn_t ivybridge_irq_handler(int irq, void *arg)
 {
 	struct drm_device *dev = (struct drm_device *) arg;
@@ -707,6 +718,14 @@ static irqreturn_t ivybridge_irq_handler(int irq, void *arg)
 
 	atomic_inc(&dev_priv->irq_received);
 
+	/* We get interrupts on unclaimed registers, so check this before we do
+	 * any I915_{READ,WRITE}. */
+	if (drm_debug && IS_HASWELL(dev) &&
+	    (I915_READ_NOTRACE(FPGA_DBG) & FPGA_DBG_RM_NOCLAIM)) {
+		DRM_ERROR("Unclaimed register before interrupt\n");
+		I915_WRITE_NOTRACE(FPGA_DBG, FPGA_DBG_RM_NOCLAIM);
+	}
+
 	/* disable master interrupt before clearing iir  */
 	de_ier = I915_READ(DEIER);
 	I915_WRITE(DEIER, de_ier & ~DE_MASTER_IRQ_CONTROL);
@@ -720,6 +739,9 @@ static irqreturn_t ivybridge_irq_handler(int irq, void *arg)
 
 	de_iir = I915_READ(DEIIR);
 	if (de_iir) {
+		if (de_iir & DE_ERR_INT_IVB)
+			ivb_err_int_handler(dev);
+
 		if (de_iir & DE_AUX_CHANNEL_A_IVB)
 			dp_aux_irq_handler(dev);
 
@@ -2006,7 +2028,8 @@ static int ivybridge_irq_postinstall(struct drm_device *dev)
 		DE_PLANEC_FLIP_DONE_IVB |
 		DE_PLANEB_FLIP_DONE_IVB |
 		DE_PLANEA_FLIP_DONE_IVB |
-		DE_AUX_CHANNEL_A_IVB;
+		DE_AUX_CHANNEL_A_IVB |
+		DE_ERR_INT_IVB;
 	u32 render_irqs;
 	u32 hotplug_mask;
 	u32 pch_irq_mask;
@@ -2014,6 +2037,7 @@ static int ivybridge_irq_postinstall(struct drm_device *dev)
 	dev_priv->irq_mask = ~display_mask;
 
 	/* should always can generate irq */
+	I915_WRITE(GEN7_ERR_INT, I915_READ(GEN7_ERR_INT));
 	I915_WRITE(DEIIR, I915_READ(DEIIR));
 	I915_WRITE(DEIMR, dev_priv->irq_mask);
 	I915_WRITE(DEIER,
@@ -2177,6 +2201,8 @@ static void ironlake_irq_uninstall(struct drm_device *dev)
 	I915_WRITE(DEIMR, 0xffffffff);
 	I915_WRITE(DEIER, 0x0);
 	I915_WRITE(DEIIR, I915_READ(DEIIR));
+	if (IS_GEN7(dev))
+		I915_WRITE(GEN7_ERR_INT, I915_READ(GEN7_ERR_INT));
 
 	I915_WRITE(GTIMR, 0xffffffff);
 	I915_WRITE(GTIER, 0x0);
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index ee30fb9..86cace1 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -3379,7 +3379,7 @@
 #define DE_PIPEA_FIFO_UNDERRUN  (1 << 0)
 
 /* More Ivybridge lolz */
-#define DE_ERR_DEBUG_IVB		(1<<30)
+#define DE_ERR_INT_IVB			(1<<30)
 #define DE_GSE_IVB			(1<<29)
 #define DE_PCH_EVENT_IVB		(1<<28)
 #define DE_DP_A_HOTPLUG_IVB		(1<<27)
-- 
1.7.10.4