drm/i915/hsw: Fix GPU hang during resume from S3-devices state
Currently resuming on HSW from S3 pm_test/devices state leads to an
unrecoverable GPU hang. Resetting the GPU during suspend fixes this. For
a full S3 cycle this change only means the reset happens earlier (before
reaching S3). For S4 the reset will happen now both during the freeze
and quiesce phases, which is a benefit since it will guarantee that the
GPU is idle before creating and loading the hibernation image.
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1476283597-580-1-git-send-email-imre.deak@intel.com
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index fdd496e..830df36 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4273,6 +4273,30 @@
*/
WARN_ON(dev_priv->gt.awake);
+ /*
+ * Neither the BIOS, ourselves or any other kernel
+ * expects the system to be in execlists mode on startup,
+ * so we need to reset the GPU back to legacy mode. And the only
+ * known way to disable logical contexts is through a GPU reset.
+ *
+ * So in order to leave the system in a known default configuration,
+ * always reset the GPU upon unload and suspend. Afterwards we then
+ * clean up the GEM state tracking, flushing off the requests and
+ * leaving the system in a known idle state.
+ *
+ * Note that is of the upmost importance that the GPU is idle and
+ * all stray writes are flushed *before* we dismantle the backing
+ * storage for the pinned objects.
+ *
+ * However, since we are uncertain that resetting the GPU on older
+ * machines is a good idea, we don't - just in case it leaves the
+ * machine in an unusable condition.
+ */
+ if (HAS_HW_CONTEXTS(dev)) {
+ int reset = intel_gpu_reset(dev_priv, ALL_ENGINES);
+ WARN_ON(reset && reset != -ENODEV);
+ }
+
return 0;
err:
