linux-kernel - [PATCH 1/2] drm/i915: Disable semaphores by default on SNB

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Date:	Mon, 26 Dec 2011 17:02:10 -0800
From:	Keith Packard <keithp@...thp.com>
To:	intel-gfx@...ts.freedesktop.org, torvalds@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	Keith Packard <keithp@...thp.com>,
	Daniel Vetter <daniel@...ll.ch>,
	Eugeni Dodonov <eugeni@...onov.net>
Subject: [PATCH 1/2] drm/i915: Disable semaphores by default on SNB

Semaphores still cause problems on some machines:

> From Udo Steinberg:
>
> With Linux-3.2-rc6 I'm frequently seeing GPU hangs when large amounts of
> text scroll in an xterm, such as when extracting a tar archive. Such as this
> one (note the timestamps):
>
>  I can reproduce it fairly easily with something
>  as simple as:
>
>	  while true; do dmesg; done

This patch turns them off on SNB while leaving them on for IVB.

Reported-by: Udo Steinberg <udo@...ervisor.org>
Cc: Daniel Vetter <daniel@...ll.ch>
Cc: Eugeni Dodonov <eugeni@...onov.net>
Signed-off-by: Keith Packard <keithp@...thp.com>
---
 drivers/gpu/drm/i915/i915_gem_execbuffer.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index c681dc1..b9da890 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -756,9 +756,9 @@ intel_enable_semaphores(struct drm_device *dev)
 	if (i915_semaphores >= 0)
 		return i915_semaphores;
 
-	/* Enable semaphores on SNB when IO remapping is off */
+	/* Disable semaphores on SNB */
 	if (INTEL_INFO(dev)->gen == 6)
-		return !intel_iommu_enabled;
+		return 0;
 
 	return 1;
 }
-- 
1.7.7.3

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