drm/i915: Defer final intel_wakeref_put to process context

As we need to acquire a mutex to serialise the final
intel_wakeref_put, we need to ensure that we are in process context at
that time. However, we want to allow operation on the intel_wakeref from
inside timer and other hardirq context, which means that need to defer
that final put to a workqueue.

Inside the final wakeref puts, we are safe to operate in any context, as
we are simply marking up the HW and state tracking for the potential
sleep. It's only the serialisation with the potential sleeping getting
that requires careful wait avoidance. This allows us to retain the
immediate processing as before (we only need to sleep over the same
races as the current mutex_lock).

v2: Add a selftest to ensure we exercise the code while lockdep watches.
v3: That test was extremely loud and complained about many things!
v4: Not a whale!

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111295
References: https://bugs.freedesktop.org/show_bug.cgi?id=111245
References: https://bugs.freedesktop.org/show_bug.cgi?id=111256
Fixes: 18398904ca9e ("drm/i915: Only recover active engines")
Fixes: 51fbd8de87dc ("drm/i915/pmu: Atomically acquire the gt_pm wakeref")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190808202758.10453-1-chris@chris-wilson.co.uk

1 files changed, 11 insertions, 27 deletions

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.c b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
index 0336204988d6..6b15e3335dd6 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_pm.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
@@ -37,28 +37,6 @@ static int __engine_unpark(struct intel_wakeref *wf)
 	return 0;
 }
 
-void intel_engine_pm_get(struct intel_engine_cs *engine)
-{
-	intel_wakeref_get(&engine->i915->runtime_pm, &engine->wakeref, __engine_unpark);
-}
-
-void intel_engine_park(struct intel_engine_cs *engine)
-{
-	/*
-	 * We are committed now to parking this engine, make sure there
-	 * will be no more interrupts arriving later and the engine
-	 * is truly idle.
-	 */
-	if (wait_for(intel_engine_is_idle(engine), 10)) {
-		struct drm_printer p = drm_debug_printer(__func__);
-
-		dev_err(engine->i915->drm.dev,
-			"%s is not idle before parking\n",
-			engine->name);
-		intel_engine_dump(engine, &p, NULL);
-	}
-}
-
 static bool switch_to_kernel_context(struct intel_engine_cs *engine)
 {
 	struct i915_request *rq;
@@ -136,12 +114,18 @@ static int __engine_park(struct intel_wakeref *wf)
 	return 0;
 }
 
-void intel_engine_pm_put(struct intel_engine_cs *engine)
-{
-	intel_wakeref_put(&engine->i915->runtime_pm, &engine->wakeref, __engine_park);
-}
+static const struct intel_wakeref_ops wf_ops = {
+	.get = __engine_unpark,
+	.put = __engine_park,
+};
 
 void intel_engine_init__pm(struct intel_engine_cs *engine)
 {
-	intel_wakeref_init(&engine->wakeref);
+	struct intel_runtime_pm *rpm = &engine->i915->runtime_pm;
+
+	intel_wakeref_init(&engine->wakeref, rpm, &wf_ops);
 }
+
+#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
+#include "selftest_engine_pm.c"
+#endif