[Intel-gfx] i915 irq storm mitigation in 3.10

[Egbert Eich]

Jan Niggemann writes:
 > Egbert, Daniel, others,
 > It's a Lenovo ThinkPad T400, the model is 7434-AG2.
 > root at muretop:~# lspci -n
 > 00:00.0 0600: 8086:2a40 (rev 07)
 > 00:02.0 0300: 8086:2a42 (rev 07)

Ok, this is a gm45.

 > 
 > 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

These logs show that interrupts are still coming thru although they
should be disabled.

Could you try if the patch below makes any difference?

Cheers,
	Egbert.

>From 70dae32e99799d15ddcedd5853514215624a8289 Mon Sep 17 00:00:00 2001
From: Egbert Eich <eich at suse.de>
Date: Mon, 22 Jul 2013 22:33:36 +0200
Subject: [PATCH] drm/i915: Make sure PORT_HOTPLUG_EN is written

Add posting read to make sure PORT_HOTPLUG_EN is written in
i915_hpd_irq_setup().

Signed-off-by: Egbert Eich <eich at suse.de>
---
 drivers/gpu/drm/i915/i915_irq.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index f708e4e..e43d809 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -2802,6 +2802,7 @@ static void i915_hpd_irq_setup(struct drm_device *dev)
 
 		/* Ignore TV since it's buggy */
 		I915_WRITE(PORT_HOTPLUG_EN, hotplug_en);
+		POSTING_READ(PORT_HOTPLUG_EN);
 	}
 }
 
-- 
1.8.1.4