[Intel-gfx] [PATCH 4/4] drm/i915/execlists: Use direct submission to restart HW after reset

[Chris Wilson]

We can bypass ksoftirqd for restarting our submission queue after a GPU
reset and so avoid any inscrutable delays.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_guc_submission.c | 24 +++++++++++++++++++++
 drivers/gpu/drm/i915/intel_lrc.c            |  2 +-
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_guc_submission.c b/drivers/gpu/drm/i915/intel_guc_submission.c
index 8f43c2fe90ca..d9f9b12a0213 100644
--- a/drivers/gpu/drm/i915/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/intel_guc_submission.c
@@ -842,6 +842,29 @@ guc_reset_prepare(struct intel_engine_cs *engine)
 	return i915_gem_find_active_request(engine);
 }
 
+static void guc_reset_finish(struct intel_engine_cs *engine)
+{
+	struct intel_engine_execlists * const execlists = &engine->execlists;
+
+	/* After a GPU reset, we may have requests to replay */
+	if (!RB_EMPTY_ROOT(&execlists->queue.rb_root))
+		tasklet_schedule(&execlists->tasklet);
+
+	/*
+	 * Flush the tasklet while we still have the forcewake to be sure
+	 * that it is not allowed to sleep before we restart and reload a
+	 * context.
+	 *
+	 * As before (with execlists_reset_prepare) we rely on the caller
+	 * serialising multiple attempts to reset so that we know that we
+	 * are the only one manipulating tasklet state.
+	 */
+	__tasklet_enable_sync_once(&execlists->tasklet);
+
+	GEM_TRACE("%s: depth->%d\n", engine->name,
+		  atomic_read(&execlists->tasklet.count));
+}
+
 /*
  * Everything below here is concerned with setup & teardown, and is
  * therefore not part of the somewhat time-critical batch-submission
@@ -1289,6 +1312,7 @@ static void guc_set_default_submission(struct intel_engine_cs *engine)
 	engine->unpark = guc_submission_unpark;
 
 	engine->reset.prepare = guc_reset_prepare;
+	engine->reset.finish = guc_reset_finish;
 
 	engine->flags &= ~I915_ENGINE_SUPPORTS_STATS;
 }
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 257d6f5f44d1..4631d38f0b6e 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1970,7 +1970,7 @@ static void execlists_reset_finish(struct intel_engine_cs *engine)
 
 	/* After a GPU reset, we may have requests to replay */
 	if (!RB_EMPTY_ROOT(&execlists->queue.rb_root))
-		tasklet_schedule(&execlists->tasklet);
+		execlists_submission_tasklet(execlists->tasklet.data);
 
 	/*
 	 * Flush the tasklet while we still have the forcewake to be sure
-- 
2.18.0