drm/i915: Mark intel_wakeref_get() as a sleeper

Assume that intel_wakeref_get() may take the mutex, and perform other
sleeping actions in the course of its callbacks and so use might_sleep()
to ensure that all callers abide. Anything that cannot sleep has to use
e.g. intel_wakeref_get_if_active() to guarantee its avoidance of the
non-atomic paths.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191121130528.309474-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/intel_gt_pm.h

@@ -22,6 +22,11 @@ static inline void intel_gt_pm_get(struct intel_gt *gt)
 	intel_wakeref_get(&gt->wakeref);
 }
 
+static inline void __intel_gt_pm_get(struct intel_gt *gt)
+{
+	__intel_wakeref_get(&gt->wakeref);
+}
+
 static inline bool intel_gt_pm_get_if_awake(struct intel_gt *gt)
 {
 	return intel_wakeref_get_if_active(&gt->wakeref);

drivers/gpu/drm/i915/gt/intel_lrc.c

@@ -1121,7 +1121,7 @@ __execlists_schedule_in(struct i915_request *rq)
 		BUILD_BUG_ON(NUM_CONTEXT_TAG > GEN12_MAX_CONTEXT_HW_ID);
 	}
 
-	intel_gt_pm_get(engine->gt);
+	__intel_gt_pm_get(engine->gt);
 	execlists_context_status_change(rq, INTEL_CONTEXT_SCHEDULE_IN);
 	intel_engine_context_in(engine);
 

drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c

@@ -529,7 +529,7 @@ static struct i915_request *schedule_in(struct i915_request *rq, int idx)
 	 * required if we generalise the inflight tracking.
 	 */
 
-	intel_gt_pm_get(rq->engine->gt);
+	__intel_gt_pm_get(rq->engine->gt);
 	return i915_request_get(rq);
 }
 

drivers/gpu/drm/i915/intel_wakeref.h

@@ -59,9 +59,7 @@ void __intel_wakeref_put_last(struct intel_wakeref *wf, unsigned long flags);
 
 /**
  * intel_wakeref_get: Acquire the wakeref
- * @i915: the drm_i915_private device
  * @wf: the wakeref
- * @fn: callback for acquired the wakeref, called only on first acquire.
  *
  * Acquire a hold on the wakeref. The first user to do so, will acquire
  * the runtime pm wakeref and then call the @fn underneath the wakeref
@@ -76,12 +74,29 @@ void __intel_wakeref_put_last(struct intel_wakeref *wf, unsigned long flags);
 static inline int
 intel_wakeref_get(struct intel_wakeref *wf)
 {
+	might_sleep();
 	if (unlikely(!atomic_inc_not_zero(&wf->count)))
 		return __intel_wakeref_get_first(wf);
 
 	return 0;
 }
 
+/**
+ * __intel_wakeref_get: Acquire the wakeref, again
+ * @wf: the wakeref
+ *
+ * Increment the wakeref counter, only valid if it is already held by
+ * the caller.
+ *
+ * See intel_wakeref_get().
+ */
+static inline void
+__intel_wakeref_get(struct intel_wakeref *wf)
+{
+	INTEL_WAKEREF_BUG_ON(atomic_read(&wf->count) <= 0);
+	atomic_inc(&wf->count);
+}
+
 /**
  * intel_wakeref_get_if_in_use: Acquire the wakeref
  * @wf: the wakeref