[Intel-gfx] [PATCH] drm/i915: Disable execlists by default for gen8

[Chris Wilson]

Bug reports are still coming in for late 4.0-rcX that indicate that
execlists causes GPU hangs following resume.

Fixes regression from
commit d7f621e50704306c348ccb192f17047f1499f9bc
Author: Oscar Mateo <oscar.mateo at intel.com>
Date:   Thu Jul 24 17:04:49 2014 +0100

    drm/i915/bdw: Enable Logical Ring Contexts (hence, Execlists)

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89308
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Oscar Mateo <oscar.mateo at intel.com>
Cc: Damien Lespiau <damien.lespiau at intel.com>
Cc: Nick Hoath <nicholas.hoath at intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Cc: Michel Thierry <michel.thierry at intel.com>
Cc: Arun Siluvery <arun.siluvery at linux.intel.com>
Cc: John Harrison <John.C.Harrison at Intel.com>
Cc: Thomas Daniel <thomas.daniel at intel.com>
Cc: stable at vger.linux.kernel
---
 drivers/gpu/drm/i915/intel_lrc.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index a3ad95b6ea51..1b289481a9b3 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -232,9 +232,15 @@ int intel_sanitize_enable_execlists(struct drm_device *dev, int enable_execlists
 	if (enable_execlists == 0)
 		return 0;
 
+#if 0
+	/* Disable execlists by default for 4.0, since we still have
+	 * issues upon resume in the wild, e.g.
+	 * https://bugs.freedesktop.org/show_bug.cgi?id=89308
+	 */
 	if (HAS_LOGICAL_RING_CONTEXTS(dev) && USES_PPGTT(dev) &&
 	    i915.use_mmio_flip >= 0)
 		return 1;
+#endif
 
 	return 0;
 }
-- 
2.1.4