drm/i915: Generalise GPU activity tracking

We currently track GPU memory usage inside VMA, such that we never
release memory used by the GPU until after it has finished accessing it.
However, we may want to track other resources aside from VMA, or we may
want to split a VMA into multiple independent regions and track each
separately. For this purpose, generalise our request tracking (akin to
struct reservation_object) so that we can embed it into other objects.

v2: Tweak error handling during selftest setup.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190205130005.2807-2-chris@chris-wilson.co.uk

1 files changed, 69 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_active.h b/drivers/gpu/drm/i915/i915_active.h
new file mode 100644
index 000000000000..0aa2628ea734
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_active.h
@@ -0,0 +1,69 @@
+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * Copyright © 2019 Intel Corporation
+ */
+
+#ifndef _I915_ACTIVE_H_
+#define _I915_ACTIVE_H_
+
+#include "i915_active_types.h"
+
+/*
+ * GPU activity tracking
+ *
+ * Each set of commands submitted to the GPU compromises a single request that
+ * signals a fence upon completion. struct i915_request combines the
+ * command submission, scheduling and fence signaling roles. If we want to see
+ * if a particular task is complete, we need to grab the fence (struct
+ * i915_request) for that task and check or wait for it to be signaled. More
+ * often though we want to track the status of a bunch of tasks, for example
+ * to wait for the GPU to finish accessing some memory across a variety of
+ * different command pipelines from different clients. We could choose to
+ * track every single request associated with the task, but knowing that
+ * each request belongs to an ordered timeline (later requests within a
+ * timeline must wait for earlier requests), we need only track the
+ * latest request in each timeline to determine the overall status of the
+ * task.
+ *
+ * struct i915_active provides this tracking across timelines. It builds a
+ * composite shared-fence, and is updated as new work is submitted to the task,
+ * forming a snapshot of the current status. It should be embedded into the
+ * different resources that need to track their associated GPU activity to
+ * provide a callback when that GPU activity has ceased, or otherwise to
+ * provide a serialisation point either for request submission or for CPU
+ * synchronisation.
+ */
+
+void i915_active_init(struct drm_i915_private *i915,
+		      struct i915_active *ref,
+		      void (*retire)(struct i915_active *ref));
+
+int i915_active_ref(struct i915_active *ref,
+		    u64 timeline,
+		    struct i915_request *rq);
+
+int i915_active_wait(struct i915_active *ref);
+
+int i915_request_await_active(struct i915_request *rq,
+			      struct i915_active *ref);
+
+bool i915_active_acquire(struct i915_active *ref);
+
+static inline void i915_active_cancel(struct i915_active *ref)
+{
+	GEM_BUG_ON(ref->count != 1);
+	ref->count = 0;
+}
+
+void i915_active_release(struct i915_active *ref);
+
+static inline bool
+i915_active_is_idle(const struct i915_active *ref)
+{
+	return !ref->count;
+}
+
+void i915_active_fini(struct i915_active *ref);
+
+#endif /* _I915_ACTIVE_H_ */