[Intel-gfx] [PATCH] drm/i915: Don't WARN nor handle unexpected hpd interrupts on gmch platforms

[Daniel Vetter]

The status bits are unconditionally set, the control bits only enable
the actual interrupt generation. Which means if we get some random
other interrupts we'll bogusly complain about them.

So restrict the WARN to platforms with a sane hotplug interrupt
handling scheme. And even more important also don't attempt to process
the hpd bit since we've detected a storm already. Instead just clear
the bit silently.

This WARN has been introduced in

commit b8f102e8bf71cacf33326360fdf9dcfd1a63925b
Author: Egbert Eich <eich at suse.de>
Date:   Fri Jul 26 14:14:24 2013 +0200

    drm/i915: Add messages useful for HPD storm detection debugging (v2)

before that we silently handled the hpd event and so partially
defeated the storm detection.

v2: Pimp commit message (Jani)

Cc: Jani Nikula <jani.nikula at linux.intel.com>
Cc: Egbert Eich <eich at suse.de>
Cc: bitlord <bitlord0xff at gmail.com>
Reported-by: bitlord <bitlord0xff at gmail.com>
Cc: stable at vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/i915/i915_irq.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 7753249b3a95..f98ba4e6e70b 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1362,10 +1362,20 @@ 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++) {
 
-		WARN_ONCE(hpd[i] & hotplug_trigger &&
-			  dev_priv->hpd_stats[i].hpd_mark == HPD_DISABLED,
-			  "Received HPD interrupt (0x%08x) on pin %d (0x%08x) although disabled\n",
-			  hotplug_trigger, i, hpd[i]);
+		if (hpd[i] & hotplug_trigger &&
+		    dev_priv->hpd_stats[i].hpd_mark == HPD_DISABLED) {
+			/*
+			 * On GMCH platforms the interrupt mask bits only
+			 * prevent irq generation, not the setting of the
+			 * hotplug bits itself. So only WARN about unexpected
+			 * interrupts on saner platforms.
+			 */
+			WARN_ONCE(INTEL_INFO(dev)->gen >= 5 && !IS_VALLEYVIEW(dev),
+				  "Received HPD interrupt (0x%08x) on pin %d (0x%08x) although disabled\n",
+				  hotplug_trigger, i, hpd[i]);
+
+			continue;
+		}
 
 		if (!(hpd[i] & hotplug_trigger) ||
 		    dev_priv->hpd_stats[i].hpd_mark != HPD_ENABLED)
-- 
1.9.2