linux-kernel - [ 05/95] drm/i915: Prevent a machine hang by checking crtc->active before loading lut

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Date:	Fri, 09 Mar 2012 11:02:07 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Alban Browaeys <prahal@...oo.com>,
	Chris Wilson <chris@...is-wilson.co.uk>,
	Jesse Barnes <jbarnes@...tuousgeek.org>
Subject: [ 05/95] drm/i915: Prevent a machine hang by checking crtc->active before loading lut

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alban Browaeys <prahal@...oo.com>

commit aed3f09db39596e539f90b11a5016aea4d8442e1 upstream.

Before loading the lut (gamma), check the active state of intel_crtc,
otherwise at least on gen2 hang ensue.

This is reproducible in Xorg via:
  xset dpms force off
then
  xgamma -rgamma 2.0 # freeze.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=44505
Signed-off-by: Alban Browaeys <prahal@...oo.com>
Signed-off-by: Chris Wilson <chris@...is-wilson.co.uk>
Reviewed-by: Jesse Barnes <jbarnes@...tuousgeek.org>
Signed-off-by: Jesse Barnes <jbarnes@...tuousgeek.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/i915/intel_display.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -5965,7 +5965,7 @@ void intel_crtc_load_lut(struct drm_crtc
 	int i;
 
 	/* The clocks have to be on to load the palette. */
-	if (!crtc->enabled)
+	if (!crtc->enabled || !intel_crtc->active)
 		return;
 
 	/* use legacy palette for Ironlake */


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