drm/i915: Don't wake the device up to check if the engine is asleep

If the entire device is powered off, we can safely assume that the
engine is also asleep (and idle).

Reported-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Fixes: a091d4ee931b ("drm/i915: Hold a wakeref for probing the ring registers")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180212093928.6005-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index 0ad9184eba978d32377596aae437b51f43ecabb5..3efc589a7f37f6d46a5221bd9e16f15f6c71a076 100644 (file)
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -1464,7 +1464,9 @@ static bool ring_is_idle(struct intel_engine_cs *engine)
        struct drm_i915_private *dev_priv = engine->i915;
        bool idle = true;
 
-       intel_runtime_pm_get(dev_priv);
+       /* If the whole device is asleep, the engine must be idle */
+       if (!intel_runtime_pm_get_if_in_use(dev_priv))
+               return true;
 
        /* First check that no commands are left in the ring */
        if ((I915_READ_HEAD(engine) & HEAD_ADDR) !=