drm/i915: Mark concurrent submissions with a weak-dependency

We recorded the dependencies for WAIT_FOR_SUBMIT in order that we could
correctly perform priority inheritance from the parallel branches to the
common trunk. However, for the purpose of timeslicing and reset
handling, the dependency is weak -- as we the pair of requests are
allowed to run in parallel and not in strict succession.

The real significance though is that this allows us to rearrange
groups of WAIT_FOR_SUBMIT linked requests along the single engine, and
so can resolve user level inter-batch scheduling dependencies from user
semaphores.

Fixes: c81471f5e95c ("drm/i915: Copy across scheduler behaviour flags across submit fences")
Testcase: igt/gem_exec_fence/submit
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: <stable@vger.kernel.org> # v5.6+
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200507155109.8892-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index bbdb0e2a45718e526ca500f1e96a634a853f56a3..dd0fd4c4cf3220088e91044867112d16f398c96c 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -1880,6 +1880,9 @@ static void defer_request(struct i915_request *rq, struct list_head * const pl)
                        struct i915_request *w =
                                container_of(p->waiter, typeof(*w), sched);
 
+                       if (p->flags & I915_DEPENDENCY_WEAK)
+                               continue;
+
                        /* Leave semaphores spinning on the other engines */
                        if (w->engine != rq->engine)
                                continue;

diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index 4d18f808fda29356e5b0c9ffff137e518b0e560e..3c38d61c90f824c66e64ade3d34c08772828df20 100644 (file)
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -1040,7 +1040,9 @@ i915_request_await_request(struct i915_request *to, struct i915_request *from)
        }
 
        if (to->engine->schedule) {
-               ret = i915_sched_node_add_dependency(&to->sched, &from->sched);
+               ret = i915_sched_node_add_dependency(&to->sched,
+                                                    &from->sched,
+                                                    I915_DEPENDENCY_EXTERNAL);
                if (ret < 0)
                        return ret;
        }
@@ -1202,7 +1204,9 @@ __i915_request_await_execution(struct i915_request *to,
 
        /* Couple the dependency tree for PI on this exposed to->fence */
        if (to->engine->schedule) {
-               err = i915_sched_node_add_dependency(&to->sched, &from->sched);
+               err = i915_sched_node_add_dependency(&to->sched,
+                                                    &from->sched,
+                                                    I915_DEPENDENCY_WEAK);
                if (err < 0)
                        return err;
        }

diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
index 37cfcf5b321b7003ea49c2239fb5e5008c1c510e..6e2d4190099fb401df5a53885befe6a534d7bebe 100644 (file)
--- a/drivers/gpu/drm/i915/i915_scheduler.c
+++ b/drivers/gpu/drm/i915/i915_scheduler.c
@@ -462,7 +462,8 @@ bool __i915_sched_node_add_dependency(struct i915_sched_node *node,
 }
 
 int i915_sched_node_add_dependency(struct i915_sched_node *node,
-                                  struct i915_sched_node *signal)
+                                  struct i915_sched_node *signal,
+                                  unsigned long flags)
 {
        struct i915_dependency *dep;
 
@@ -473,8 +474,7 @@ int i915_sched_node_add_dependency(struct i915_sched_node *node,
        local_bh_disable();
 
        if (!__i915_sched_node_add_dependency(node, signal, dep,
-                                             I915_DEPENDENCY_EXTERNAL |
-                                             I915_DEPENDENCY_ALLOC))
+                                             flags | I915_DEPENDENCY_ALLOC))
                i915_dependency_free(dep);
 
        local_bh_enable(); /* kick submission tasklet */

diff --git a/drivers/gpu/drm/i915/i915_scheduler.h b/drivers/gpu/drm/i915/i915_scheduler.h
index d1dc4efef77b562f3b044050ddab332ed64ab2fe..6f0bf00fc5690d361800454029bbea703b393790 100644 (file)
--- a/drivers/gpu/drm/i915/i915_scheduler.h
+++ b/drivers/gpu/drm/i915/i915_scheduler.h
@@ -34,7 +34,8 @@ bool __i915_sched_node_add_dependency(struct i915_sched_node *node,
                                      unsigned long flags);
 
 int i915_sched_node_add_dependency(struct i915_sched_node *node,
-                                  struct i915_sched_node *signal);
+                                  struct i915_sched_node *signal,
+                                  unsigned long flags);
 
 void i915_sched_node_fini(struct i915_sched_node *node);
 

diff --git a/drivers/gpu/drm/i915/i915_scheduler_types.h b/drivers/gpu/drm/i915/i915_scheduler_types.h
index d18e7055005424e67516e59f6a8a214a6978abf0..7186875088a0a285c1f05a13df5846db478f4162 100644 (file)
--- a/drivers/gpu/drm/i915/i915_scheduler_types.h
+++ b/drivers/gpu/drm/i915/i915_scheduler_types.h
@@ -78,6 +78,7 @@ struct i915_dependency {
        unsigned long flags;
 #define I915_DEPENDENCY_ALLOC          BIT(0)
 #define I915_DEPENDENCY_EXTERNAL       BIT(1)
+#define I915_DEPENDENCY_WEAK           BIT(2)
 };
 
 #endif /* _I915_SCHEDULER_TYPES_H_ */