[Intel-gfx] [PATCH] drm/i915: Prevent a machine hang by checking crtc->active before loading lut

[Chris Wilson]

From: Alban Browaeys <prahal at yahoo.com>

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 at yahoo.com>
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: stable at kernel.org
---
 drivers/gpu/drm/i915/intel_display.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index cdcf99b..4b48de5 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6268,7 +6268,7 @@ void intel_crtc_load_lut(struct drm_crtc *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 */
-- 
1.7.9.1