drm/i915: Prevent a machine hang by checking crtc->active before loading lut

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@yahoo.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index fed87d6..e4b2586 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -5265,7 +5265,7 @@ 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 */