[Intel-gfx] i915 irq storm mitigation in 3.10

[Egbert Eich]

Hi Jan -

Jan Niggemann writes:
 > 
 > As to the log: I messed up the kernel parameters this morning... was 
 > out of coffee this morning and my 1,5y daughter played around me :-)
 > 
 > Here's my kernel log with drm.debug and printk.time enabled:
 > Uncompressed (22M): http://files.hz6.de/kern_20130722.log
 > bzip2'd (some 600 KB): http://files.hz6.de/kern_20130722.log.bz2

I've looked at the logs a bit more. Here's a patch adding some more
debug information. Would you please apply this to your 3.10 kernel
and generate a log file the same way as you did before.
The driver will be even more chatty - but I don't expect any problems
from this.

Cheers,
	Egbert.

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index e43d809..46bb77c 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -919,6 +919,11 @@ static inline void intel_hpd_irq_handler(struct drm_device *dev,
 	spin_lock(&dev_priv->irq_lock);
 	for (i = 1; i < HPD_NUM_PINS; i++) {
 
+		if (IS_G4X(dev) && (hpd[i] & hotplug_trigger) &&
+		    dev_priv->hpd_stats[i].hpd_mark != HPD_ENABLED)
+			DRM_DEBUG_KMS("Received HPD intterupt although disabled\n",
+				      I915_READ(PORT_HOTPLUG_EN));
+
 		if (!(hpd[i] & hotplug_trigger) ||
 		    dev_priv->hpd_stats[i].hpd_mark != HPD_ENABLED)
 			continue;
@@ -929,6 +934,8 @@ static inline void intel_hpd_irq_handler(struct drm_device *dev,
 				   + msecs_to_jiffies(HPD_STORM_DETECT_PERIOD))) {
 			dev_priv->hpd_stats[i].hpd_last_jiffies = jiffies;
 			dev_priv->hpd_stats[i].hpd_cnt = 0;
+			DRM_DEBUG_KMS("Received HPD interrupt on PIN %d - jiffies: %d\n", i,
+				      dev_priv->hpd_stats[i].hpd_last_jiffies);
 		} else if (dev_priv->hpd_stats[i].hpd_cnt > HPD_STORM_THRESHOLD) {
 			dev_priv->hpd_stats[i].hpd_mark = HPD_MARK_DISABLED;
 			dev_priv->hpd_event_bits &= ~(1 << i);
@@ -936,6 +943,8 @@ static inline void intel_hpd_irq_handler(struct drm_device *dev,
 			storm_detected = true;
 		} else {
 			dev_priv->hpd_stats[i].hpd_cnt++;
+			DRM_DEBUG_KMS("Received HPD interrupt on PIN %d - cnt: %d\n", i,
+				      dev_priv->hpd_stats[i].hpd_cnt);
 		}
 	}