[PATCH v.2 06/12] DRM/i915: Add HPD IRQ storm detection.

[Egbert Eich <eich@suse.de>]

Add a hotplug IRQ storm detection (triggered when a hotplug interrupt
fires more than 5 times / sec).
Mask out this specific interrupt and revert to polling on the associated
output.
Rationale:
Despite of the many attempts to fix the problem with noisy hotplug
interrupt lines we are still seeing systems which have issues:
Once cause of noise seems to be bad routing of the hotplug line
on the board: cross talk from other signals seems to cause erronous
hotplug interrupts. This has been documented as an erratum for the
the i945GM chipset and thus hotplug support was disabled for this
chipset model but others seem to have this problem, too.

We have seen this issue on a G35 motherboard for example:
Even different motherboards of the same model seem to behave
differently: while some only see only around 10-100 interrupts/s
others seem to see 5k or more.
We've also observed a dependency on the selected video mode.

Also on certain laptops interrupt noise seems to occur duing
battery charging when the battery is at a certain charge levels.

Thus we add a simple algorithm here that detects an 'interrupt storm'
condition.

Signed-off-by: Egbert Eich <eich@suse.de>
---
 drivers/gpu/drm/i915/i915_drv.h |    9 +++++
 drivers/gpu/drm/i915/i915_irq.c |   63 +++++++++++++++++++++++++++++++-------
 2 files changed, 60 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index d8604a6..6ca742d 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1059,6 +1059,15 @@ typedef struct drm_i915_private {
 	/* Old dri1 support infrastructure, beware the dragons ya fools entering
 	 * here! */
 	struct i915_dri1_state dri1;
+	struct {
+		unsigned long hpd_last_jiffies;
+		int hpd_cnt;
+		enum {
+			HPD_ENABLED = 0,
+			HPD_DISABLED = 1,
+			HPD_MARK_DISABLED = 2
+		} hpd_mark;
+	} hpd_stats[HPD_NUM_PINS];
 } drm_i915_private_t;
 
 /* Iterate over initialised rings */
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index c6ae7ae..08a0934 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -587,6 +587,34 @@ static void gen6_queue_rps_work(struct drm_i915_private *dev_priv,
 	queue_work(dev_priv->wq, &dev_priv->rps.work);
 }
 
+static inline void hotplug_irq_storm_detect(struct drm_device *dev,
+					    u32 hotplug_trigger,
+					    const u32 *hpd)
+{
+	drm_i915_private_t *dev_priv = dev->dev_private;
+	unsigned long irqflags;
+	int i;
+
+	spin_lock_irqsave(&dev_priv->irq_lock, irqflags);
+
+	for (i = 1; i < HPD_NUM_PINS; i++) {
+		if ((hpd[i] & hotplug_trigger) &&
+		    dev_priv->hpd_stats[i].hpd_mark == HPD_ENABLED) {
+			if (jiffies > (dev_priv->hpd_stats[i].hpd_last_jiffies + msecs_to_jiffies(1000)) ||
+			    jiffies < dev_priv->hpd_stats[i].hpd_last_jiffies) {
+				dev_priv->hpd_stats[i].hpd_last_jiffies = jiffies;
+				dev_priv->hpd_stats[i].hpd_cnt = 0;
+			} else if (dev_priv->hpd_stats[i].hpd_cnt > 5) {
+				dev_priv->hpd_stats[i].hpd_mark = HPD_MARK_DISABLED;
+				DRM_DEBUG_KMS("HPD interrupt storm detected on  PIN %d\n", i);
+			} else
+				dev_priv->hpd_stats[i].hpd_cnt++;
+		}
+	}
+
+	spin_unlock_irqrestore(&dev_priv->irq_lock, irqflags);
+}
+
 static void gmbus_irq_handler(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = (drm_i915_private_t *) dev->dev_private;
@@ -655,13 +683,15 @@ static irqreturn_t valleyview_irq_handler(int irq, void *arg)
 		/* Consume port.  Then clear IIR or we'll miss events */
 		if (iir & I915_DISPLAY_PORT_INTERRUPT) {
 			u32 hotplug_status = I915_READ(PORT_HOTPLUG_STAT);
+			u32 hotplug_trigger = hotplug_status & HOTPLUG_INT_STATUS_I915;
 
 			DRM_DEBUG_DRIVER("hotplug event received, stat 0x%08x\n",
 					 hotplug_status);
-			if (hotplug_status & HOTPLUG_INT_STATUS_I915)
+			if (hotplug_trigger) {
+				hotplug_irq_storm_detect(dev, hotplug_trigger, hpd_status_i915);
 				queue_work(dev_priv->wq,
 					   &dev_priv->hotplug_work);
-
+			}
 			I915_WRITE(PORT_HOTPLUG_STAT, hotplug_status);
 			I915_READ(PORT_HOTPLUG_STAT);
 		}
@@ -685,10 +715,12 @@ static void ibx_irq_handler(struct drm_device *dev, u32 pch_iir)
 {
 	drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
 	int pipe;
+	u32 hotplug_trigger = pch_iir & SDE_HOTPLUG_MASK;
 
-	if (pch_iir & SDE_HOTPLUG_MASK)
+	if (hotplug_trigger) {
+		hotplug_irq_storm_detect(dev, hotplug_trigger, hpd_ibx);
 		queue_work(dev_priv->wq, &dev_priv->hotplug_work);
-
+	}
 	if (pch_iir & SDE_AUDIO_POWER_MASK)
 		DRM_DEBUG_DRIVER("PCH audio power change on port %d\n",
 				 (pch_iir & SDE_AUDIO_POWER_MASK) >>
@@ -731,10 +763,12 @@ static void cpt_irq_handler(struct drm_device *dev, u32 pch_iir)
 {
 	drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
 	int pipe;
+	u32 hotplug_trigger = pch_iir & SDE_HOTPLUG_MASK_CPT;
 
-	if (pch_iir & SDE_HOTPLUG_MASK_CPT)
+	if (hotplug_trigger) {
+		hotplug_irq_storm_detect(dev, hotplug_trigger, hpd_cpt);
 		queue_work(dev_priv->wq, &dev_priv->hotplug_work);
-
+	}
 	if (pch_iir & SDE_AUDIO_POWER_MASK_CPT)
 		DRM_DEBUG_DRIVER("PCH audio power change on port %d\n",
 				 (pch_iir & SDE_AUDIO_POWER_MASK_CPT) >>
@@ -2477,13 +2511,15 @@ static irqreturn_t i915_irq_handler(int irq, void *arg)
 		if ((I915_HAS_HOTPLUG(dev)) &&
 		    (iir & I915_DISPLAY_PORT_INTERRUPT)) {
 			u32 hotplug_status = I915_READ(PORT_HOTPLUG_STAT);
+			u32 hotplug_trigger = hotplug_status & HOTPLUG_INT_STATUS_I915;
 
 			DRM_DEBUG_DRIVER("hotplug event received, stat 0x%08x\n",
 				  hotplug_status);
-			if (hotplug_status & HOTPLUG_INT_STATUS_I915)
+			if (hotplug_trigger) {
+				hotplug_irq_storm_detect(dev, hotplug_trigger, hpd_status_i915);
 				queue_work(dev_priv->wq,
 					   &dev_priv->hotplug_work);
-
+			}
 			I915_WRITE(PORT_HOTPLUG_STAT, hotplug_status);
 			POSTING_READ(PORT_HOTPLUG_STAT);
 		}
@@ -2710,15 +2746,18 @@ static irqreturn_t i965_irq_handler(int irq, void *arg)
 		/* Consume port.  Then clear IIR or we'll miss events */
 		if (iir & I915_DISPLAY_PORT_INTERRUPT) {
 			u32 hotplug_status = I915_READ(PORT_HOTPLUG_STAT);
+			u32 hotplug_trigger = hotplug_status & (IS_G4X(dev) ?
+								  HOTPLUG_INT_STATUS_G4X :
+								  HOTPLUG_INT_STATUS_I965);
 
 			DRM_DEBUG_DRIVER("hotplug event received, stat 0x%08x\n",
 				  hotplug_status);
-			if (hotplug_status & (IS_G4X(dev) ?
-					      HOTPLUG_INT_STATUS_G4X :
-					      HOTPLUG_INT_STATUS_I965))
+			if (hotplug_trigger) {
+				hotplug_irq_storm_detect(dev, hotplug_trigger,
+							 IS_G4X(dev) ? hpd_status_gen4 : hpd_status_i965);
 				queue_work(dev_priv->wq,
 					   &dev_priv->hotplug_work);
-
+			}
 			I915_WRITE(PORT_HOTPLUG_STAT, hotplug_status);
 			I915_READ(PORT_HOTPLUG_STAT);
 		}
-- 
1.7.7