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

Web:        https://git.kernel.org/torvalds/c/7292b9e6586534fb43e4316ad8b508bf3d1212f7
Commit:     7292b9e6586534fb43e4316ad8b508bf3d1212f7
Parent:     33afe065b66f226ee5f90ab24ff55799c896e381
Refname:    refs/heads/master
Author:     Chris Wilson <[email protected]>
AuthorDate: Mon Feb 12 09:39:28 2018 +0000
Committer:  Rodrigo Vivi <[email protected]>
CommitDate: Mon Feb 12 23:35:03 2018 -0800

    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 <[email protected]>
    Fixes: a091d4ee931b ("drm/i915: Hold a wakeref for probing the ring registers")
    Signed-off-by: Chris Wilson <[email protected]>
    Cc: Tvrtko Ursulin <[email protected]>
    Cc: Mika Kuoppala <[email protected]>
    Reviewed-by: Mika Kuoppala <[email protected]>
    Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
    (cherry picked from commit 74d00d28a15c8452f65de0a9477b52d95639cc63)
    Signed-off-by: Rodrigo Vivi <[email protected]>
---
 drivers/gpu/drm/i915/intel_engine_cs.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index d790bdc227ff..acc661aa9c0c 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -1458,7 +1458,9 @@ 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) !=
--
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