[PATCH v3 3/3] drm/i915/gt: Timeout when waiting for idle in suspending

[Alan Previn]

When suspending, add a timeout when calling
intel_gt_pm_wait_for_idle else if we have a lost
G2H event that holds a wakeref (which would be
indicative of a bug elsewhere in the driver),
driver will at least complete the suspend-resume
cycle, (albeit not hitting all the targets for
low power hw counters), instead of hanging in the kernel.

Signed-off-by: Alan Previn <alan.previn.teres.alexis at intel.com>
Tested-by: Mousumi Jana <mousumi.jana at intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
---
 drivers/gpu/drm/i915/gt/intel_engine_cs.c |  2 +-
 drivers/gpu/drm/i915/gt/intel_gt_pm.c     |  7 ++++++-
 drivers/gpu/drm/i915/gt/intel_gt_pm.h     |  7 ++++++-
 drivers/gpu/drm/i915/intel_wakeref.c      | 14 ++++++++++----
 drivers/gpu/drm/i915/intel_wakeref.h      |  6 ++++--
 5 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index dfb69fc977a0..4811f3be0332 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -688,7 +688,7 @@ void intel_engines_release(struct intel_gt *gt)
 		if (!engine->release)
 			continue;
 
-		intel_wakeref_wait_for_idle(&engine->wakeref);
+		intel_wakeref_wait_for_idle(&engine->wakeref, 0);
 		GEM_BUG_ON(intel_engine_pm_is_awake(engine));
 
 		engine->release(engine);
diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.c b/drivers/gpu/drm/i915/gt/intel_gt_pm.c
index 5a942af0a14e..ca46aee72573 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_pm.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.c
@@ -289,6 +289,8 @@ int intel_gt_resume(struct intel_gt *gt)
 
 static void wait_for_suspend(struct intel_gt *gt)
 {
+	int timeout_ms = CONFIG_DRM_I915_MAX_REQUEST_BUSYWAIT ? : 10000;
+
 	if (!intel_gt_pm_is_awake(gt))
 		return;
 
@@ -301,7 +303,10 @@ static void wait_for_suspend(struct intel_gt *gt)
 		intel_gt_retire_requests(gt);
 	}
 
-	intel_gt_pm_wait_for_idle(gt);
+	/* we are suspending, so we shouldn't be waiting forever */
+	if (intel_gt_pm_wait_timeout_for_idle(gt, timeout_ms) == -ETIMEDOUT)
+		gt_warn(gt, "bailing from %s after %d milisec timeout\n",
+			__func__, timeout_ms);
 }
 
 void intel_gt_suspend_prepare(struct intel_gt *gt)
diff --git a/drivers/gpu/drm/i915/gt/intel_gt_pm.h b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
index 6c9a46452364..5358acc2b5b1 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_pm.h
+++ b/drivers/gpu/drm/i915/gt/intel_gt_pm.h
@@ -68,7 +68,12 @@ static inline void intel_gt_pm_might_put(struct intel_gt *gt)
 
 static inline int intel_gt_pm_wait_for_idle(struct intel_gt *gt)
 {
-	return intel_wakeref_wait_for_idle(&gt->wakeref);
+	return intel_wakeref_wait_for_idle(&gt->wakeref, 0);
+}
+
+static inline int intel_gt_pm_wait_timeout_for_idle(struct intel_gt *gt, int timeout_ms)
+{
+	return intel_wakeref_wait_for_idle(&gt->wakeref, timeout_ms);
 }
 
 void intel_gt_pm_init_early(struct intel_gt *gt);
diff --git a/drivers/gpu/drm/i915/intel_wakeref.c b/drivers/gpu/drm/i915/intel_wakeref.c
index 718f2f1b6174..383a37521415 100644
--- a/drivers/gpu/drm/i915/intel_wakeref.c
+++ b/drivers/gpu/drm/i915/intel_wakeref.c
@@ -111,14 +111,20 @@ void __intel_wakeref_init(struct intel_wakeref *wf,
 			 "wakeref.work", &key->work, 0);
 }
 
-int intel_wakeref_wait_for_idle(struct intel_wakeref *wf)
+int intel_wakeref_wait_for_idle(struct intel_wakeref *wf, int timeout_ms)
 {
-	int err;
+	int err = 0;
 
 	might_sleep();
 
-	err = wait_var_event_killable(&wf->wakeref,
-				      !intel_wakeref_is_active(wf));
+	if (!timeout_ms)
+		err = wait_var_event_killable(&wf->wakeref,
+					      !intel_wakeref_is_active(wf));
+	else if (wait_var_event_timeout(&wf->wakeref,
+					!intel_wakeref_is_active(wf),
+					msecs_to_jiffies(timeout_ms)) < 1)
+		err = -ETIMEDOUT;
+
 	if (err)
 		return err;
 
diff --git a/drivers/gpu/drm/i915/intel_wakeref.h b/drivers/gpu/drm/i915/intel_wakeref.h
index ec881b097368..302694a780d2 100644
--- a/drivers/gpu/drm/i915/intel_wakeref.h
+++ b/drivers/gpu/drm/i915/intel_wakeref.h
@@ -251,15 +251,17 @@ __intel_wakeref_defer_park(struct intel_wakeref *wf)
 /**
  * intel_wakeref_wait_for_idle: Wait until the wakeref is idle
  * @wf: the wakeref
+ * @timeout_ms: Timeout in ms, 0 means never timeout.
  *
  * Wait for the earlier asynchronous release of the wakeref. Note
  * this will wait for any third party as well, so make sure you only wait
  * when you have control over the wakeref and trust no one else is acquiring
  * it.
  *
- * Return: 0 on success, error code if killed.
+ * Returns 0 on success, -ETIMEDOUT upon a timeout, or the unlikely
+ * error propagation from wait_var_event_killable if timeout_ms is 0.
  */
-int intel_wakeref_wait_for_idle(struct intel_wakeref *wf);
+int intel_wakeref_wait_for_idle(struct intel_wakeref *wf, int timeout_ms);
 
 struct intel_wakeref_auto {
 	struct drm_i915_private *i915;
-- 
2.39.0