drm/i915/execlists: Clear user-active flag on preemption completion

When cancelling the requests and clearing out the ports following a
successful preemption completion, also clear the active flag. I had
assumed that all preemptions would be followed by an immediate dequeue
(preserving the active user flag), but under rare circumstances we may
be triggering a preemption for the second port only for it to have
completed before the preemotion kicks in; leaving execlists->active set
even though the system is now idle.

We can clear the flag inside the common execlists_cancel_port_requests()
as the other users also expect the semantics of active being cleared.

Fixes: f6322eddaff7 ("drm/i915/preemption: Allow preemption between submission ports")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180324125829.27026-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index b4ab06b05e583c2f020c5c363cadf1ad56d6fa33..9c84af53db948841a8c3eee19f51c46869381e46 100644 (file)
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -577,6 +577,8 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
                 * know the next preemption status we see corresponds
                 * to this ELSP update.
                 */
+               GEM_BUG_ON(!execlists_is_active(execlists,
+                                               EXECLISTS_ACTIVE_USER));
                GEM_BUG_ON(!port_count(&port[0]));
                if (port_count(&port[0]) > 1)
                        goto unlock;
@@ -738,6 +740,8 @@ execlists_cancel_port_requests(struct intel_engine_execlists * const execlists)
                memset(port, 0, sizeof(*port));
                port++;
        }
+
+       execlists_clear_active(execlists, EXECLISTS_ACTIVE_USER);
 }
 
 static void clear_gtiir(struct intel_engine_cs *engine)
@@ -1042,6 +1046,11 @@ static void execlists_submission_tasklet(unsigned long data)
 
        if (fw)
                intel_uncore_forcewake_put(dev_priv, execlists->fw_domains);
+
+       /* If the engine is now idle, so should be the flag; and vice versa. */
+       GEM_BUG_ON(execlists_is_active(&engine->execlists,
+                                      EXECLISTS_ACTIVE_USER) ==
+                  !port_isset(engine->execlists.port));
 }
 
 static void queue_request(struct intel_engine_cs *engine,