[PATCH 33/33] preempt-timeout

[Chris Wilson]

---
 drivers/gpu/drm/i915/Kconfig.profile |  4 +++
 drivers/gpu/drm/i915/gt/intel_lrc.c  | 50 ++++++++++++++++++++++++++--
 2 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/Kconfig.profile b/drivers/gpu/drm/i915/Kconfig.profile
index 0e5db98da8f3..807df2c25ed5 100644
--- a/drivers/gpu/drm/i915/Kconfig.profile
+++ b/drivers/gpu/drm/i915/Kconfig.profile
@@ -11,3 +11,7 @@ config DRM_I915_SPIN_REQUEST
 	  May be 0 to disable the initial spin. In practice, we estimate
 	  the cost of enabling the interrupt (if currently disabled) to be
 	  a few microseconds.
+
+config DRM_I915_PREEMPT_TIMEOUT
+	int
+	default 10 # microseconds
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index 109b32c6aead..b6d54a3a2897 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -1218,6 +1218,11 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
 		*port = execlists_schedule_in(last, port - execlists->pending);
 		memset(port + 1, 0, (last_port - port) * sizeof(*port));
 		execlists_submit_ports(engine);
+
+		if (CONFIG_DRM_I915_PREEMPT_TIMEOUT) {
+			mod_timer(&execlists->timer,
+				  jiffies + msecs_to_jiffies_timeout(CONFIG_DRM_I915_PREEMPT_TIMEOUT));
+		}
 	}
 }
 
@@ -1373,13 +1378,49 @@ static void process_csb(struct intel_engine_cs *engine)
 	invalidate_csb_entries(&buf[0], &buf[num_entries - 1]);
 }
 
-static void __execlists_submission_tasklet(struct intel_engine_cs *const engine)
+static bool __execlists_submission_tasklet(struct intel_engine_cs *const engine)
 {
 	lockdep_assert_held(&engine->active.lock);
 
 	process_csb(engine);
-	if (!engine->execlists.pending[0])
+	if (!engine->execlists.pending[0]) {
 		execlists_dequeue(engine);
+		return true;
+	}
+
+	return false;
+}
+
+static void preempt_reset(struct intel_engine_cs *engine)
+{
+	const unsigned int bit = I915_RESET_ENGINE + engine->id;
+	unsigned long *lock = &engine->i915->gpu_error.flags;
+	unsigned long flags;
+
+	if (test_and_set_bit(bit, lock))
+		return;
+
+	tasklet_disable_nosync(&engine->execlists.tasklet);
+	spin_unlock(&engine->active.lock);
+
+	i915_reset_engine(engine, "preemption timed out");
+
+	spin_lock_irqsave(&engine->active.lock, flags);
+	tasklet_enable(&engine->execlists.tasklet);
+
+	clear_bit(bit, lock);
+	wake_up_bit(lock, bit);
+}
+
+static bool preempt_timeout(struct intel_engine_cs *const engine)
+{
+	if (!CONFIG_DRM_I915_PREEMPT_TIMEOUT)
+		return false;
+
+	if (!intel_engine_has_preemption(engine))
+		return false;
+
+	return !timer_pending(&engine->execlists.timer);
 }
 
 /*
@@ -1392,7 +1433,10 @@ static void execlists_submission_tasklet(unsigned long data)
 	unsigned long flags;
 
 	spin_lock_irqsave(&engine->active.lock, flags);
-	__execlists_submission_tasklet(engine);
+
+	if (!__execlists_submission_tasklet(engine) && preempt_timeout(engine))
+		preempt_reset(engine);
+
 	spin_unlock_irqrestore(&engine->active.lock, flags);
 }
 
-- 
2.20.1