drm/i915/execlists: Flush the tasklet on parking

Tidy up the cleanup sequence by always ensure that the tasklet is
flushed on parking (before we cleanup). The parking provides a
convenient point to ensure that the backend is truly idle.

v2: Do the full check for idleness before parking, to be sure we flush
any residual interrupt.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190503080942.30151-1-chris@chris-wilson.co.uk

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

@@ -1094,6 +1094,8 @@ bool intel_engine_is_idle(struct intel_engine_cs *engine)
 	if (READ_ONCE(engine->execlists.active)) {
 		struct tasklet_struct *t = &engine->execlists.tasklet;
 
+		synchronize_hardirq(engine->i915->drm.irq);
+
 		local_bh_disable();
 		if (tasklet_trylock(t)) {
 			/* Must wait for any GPU reset in progress. */

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

@@ -10,7 +10,7 @@
 #include "intel_engine_pm.h"
 #include "intel_gt_pm.h"
 
-static int intel_engine_unpark(struct intel_wakeref *wf)
+static int __engine_unpark(struct intel_wakeref *wf)
 {
 	struct intel_engine_cs *engine =
 		container_of(wf, typeof(*engine), wakeref);
@@ -37,7 +37,24 @@ static int intel_engine_unpark(struct intel_wakeref *wf)
 
 void intel_engine_pm_get(struct intel_engine_cs *engine)
 {
-	intel_wakeref_get(engine->i915, &engine->wakeref, intel_engine_unpark);
+	intel_wakeref_get(engine->i915, &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)
@@ -56,7 +73,7 @@ static bool switch_to_kernel_context(struct intel_engine_cs *engine)
 	 * Note, we do this without taking the timeline->mutex. We cannot
 	 * as we may be called while retiring the kernel context and so
 	 * already underneath the timeline->mutex. Instead we rely on the
-	 * exclusive property of the intel_engine_park that prevents anyone
+	 * exclusive property of the __engine_park that prevents anyone
 	 * else from creating a request on this engine. This also requires
 	 * that the ring is empty and we avoid any waits while constructing
 	 * the context, as they assume protection by the timeline->mutex.
@@ -76,7 +93,7 @@ static bool switch_to_kernel_context(struct intel_engine_cs *engine)
 	return false;
 }
 
-static int intel_engine_park(struct intel_wakeref *wf)
+static int __engine_park(struct intel_wakeref *wf)
 {
 	struct intel_engine_cs *engine =
 		container_of(wf, typeof(*engine), wakeref);
@@ -114,7 +131,7 @@ static int intel_engine_park(struct intel_wakeref *wf)
 
 void intel_engine_pm_put(struct intel_engine_cs *engine)
 {
-	intel_wakeref_put(engine->i915, &engine->wakeref, intel_engine_park);
+	intel_wakeref_put(engine->i915, &engine->wakeref, __engine_park);
 }
 
 void intel_engine_init__pm(struct intel_engine_cs *engine)

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

@@ -13,6 +13,8 @@ struct intel_engine_cs;
 void intel_engine_pm_get(struct intel_engine_cs *engine);
 void intel_engine_pm_put(struct intel_engine_cs *engine);
 
+void intel_engine_park(struct intel_engine_cs *engine);
+
 void intel_engine_init__pm(struct intel_engine_cs *engine);
 
 int intel_engines_resume(struct drm_i915_private *i915);

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

@@ -136,6 +136,7 @@
 #include "i915_drv.h"
 #include "i915_gem_render_state.h"
 #include "i915_vgpu.h"
+#include "intel_engine_pm.h"
 #include "intel_lrc_reg.h"
 #include "intel_mocs.h"
 #include "intel_reset.h"
@@ -2331,6 +2332,11 @@ static int gen8_init_rcs_context(struct i915_request *rq)
 	return i915_gem_render_state_emit(rq);
 }
 
+static void execlists_park(struct intel_engine_cs *engine)
+{
+	intel_engine_park(engine);
+}
+
 void intel_execlists_set_default_submission(struct intel_engine_cs *engine)
 {
 	engine->submit_request = execlists_submit_request;
@@ -2342,7 +2348,7 @@ void intel_execlists_set_default_submission(struct intel_engine_cs *engine)
 	engine->reset.reset = execlists_reset;
 	engine->reset.finish = execlists_reset_finish;
 
-	engine->park = NULL;
+	engine->park = execlists_park;
 	engine->unpark = NULL;
 
 	engine->flags |= I915_ENGINE_SUPPORTS_STATS;
@@ -2355,14 +2361,6 @@ void intel_execlists_set_default_submission(struct intel_engine_cs *engine)
 
 static void execlists_destroy(struct intel_engine_cs *engine)
 {
-	/*
-	 * Tasklet cannot be active at this point due intel_mark_active/idle
-	 * so this is just for documentation.
-	 */
-	if (GEM_DEBUG_WARN_ON(test_bit(TASKLET_STATE_SCHED,
-				       &engine->execlists.tasklet.state)))
-		tasklet_kill(&engine->execlists.tasklet);
-
 	intel_engine_cleanup_common(engine);
 	lrc_destroy_wa_ctx(engine);
 	kfree(engine);

drivers/gpu/drm/i915/intel_guc_submission.c

@@ -25,6 +25,7 @@
 #include <linux/circ_buf.h>
 #include <trace/events/dma_fence.h>
 
+#include "gt/intel_engine_pm.h"
 #include "gt/intel_lrc_reg.h"
 
 #include "intel_guc_submission.h"
@@ -1363,6 +1364,7 @@ static void guc_interrupts_release(struct drm_i915_private *dev_priv)
 
 static void guc_submission_park(struct intel_engine_cs *engine)
 {
+	intel_engine_park(engine);
 	intel_engine_unpin_breadcrumbs_irq(engine);
 	engine->flags &= ~I915_ENGINE_NEEDS_BREADCRUMB_TASKLET;
 }