drm/i915: Split i915_gem_timeline into individual timelines

We need to move to a more flexible timeline that doesn't assume one
fence context per engine, and so allow for a single timeline to be used
across a combination of engines. This means that preallocating a fence
context per engine is now a hindrance, and so we want to introduce the
singular timeline. From the code perspective, this has the notable
advantage of clearing up a lot of mirky semantics and some clumsy
pointer chasing.

By splitting the timeline up into a single entity rather than an array
of per-engine timelines, we can realise the goal of the previous patch
of tracking the timeline alongside the ring.

v2: Tweak wait_for_idle to stop the compiling thinking that ret may be
uninitialised.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180502163839.3248-2-chris@chris-wilson.co.uk

1 files changed, 126 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_timeline.h b/drivers/gpu/drm/i915/i915_timeline.h
new file mode 100644
index 000000000000..dc2a4632faa7
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_timeline.h
@@ -0,0 +1,126 @@
+/*
+ * Copyright © 2016 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ */
+
+#ifndef I915_TIMELINE_H
+#define I915_TIMELINE_H
+
+#include <linux/list.h>
+#include <linux/kref.h>
+
+#include "i915_request.h"
+#include "i915_syncmap.h"
+#include "i915_utils.h"
+
+struct i915_timeline {
+	u64 fence_context;
+	u32 seqno;
+
+	spinlock_t lock;
+
+	/**
+	 * List of breadcrumbs associated with GPU requests currently
+	 * outstanding.
+	 */
+	struct list_head requests;
+
+	/* Contains an RCU guarded pointer to the last request. No reference is
+	 * held to the request, users must carefully acquire a reference to
+	 * the request using i915_gem_active_get_request_rcu(), or hold the
+	 * struct_mutex.
+	 */
+	struct i915_gem_active last_request;
+
+	/**
+	 * We track the most recent seqno that we wait on in every context so
+	 * that we only have to emit a new await and dependency on a more
+	 * recent sync point. As the contexts may be executed out-of-order, we
+	 * have to track each individually and can not rely on an absolute
+	 * global_seqno. When we know that all tracked fences are completed
+	 * (i.e. when the driver is idle), we know that the syncmap is
+	 * redundant and we can discard it without loss of generality.
+	 */
+	struct i915_syncmap *sync;
+	/**
+	 * Separately to the inter-context seqno map above, we track the last
+	 * barrier (e.g. semaphore wait) to the global engine timelines. Note
+	 * that this tracks global_seqno rather than the context.seqno, and
+	 * so it is subject to the limitations of hw wraparound and that we
+	 * may need to revoke global_seqno (on pre-emption).
+	 */
+	u32 global_sync[I915_NUM_ENGINES];
+
+	struct list_head link;
+	const char *name;
+
+	struct kref kref;
+};
+
+void i915_timeline_init(struct drm_i915_private *i915,
+			struct i915_timeline *tl,
+			const char *name);
+void i915_timeline_fini(struct i915_timeline *tl);
+
+struct i915_timeline *
+i915_timeline_create(struct drm_i915_private *i915, const char *name);
+
+static inline struct i915_timeline *
+i915_timeline_get(struct i915_timeline *timeline)
+{
+	kref_get(&timeline->kref);
+	return timeline;
+}
+
+void __i915_timeline_free(struct kref *kref);
+static inline void i915_timeline_put(struct i915_timeline *timeline)
+{
+	kref_put(&timeline->kref, __i915_timeline_free);
+}
+
+static inline int __i915_timeline_sync_set(struct i915_timeline *tl,
+					   u64 context, u32 seqno)
+{
+	return i915_syncmap_set(&tl->sync, context, seqno);
+}
+
+static inline int i915_timeline_sync_set(struct i915_timeline *tl,
+					 const struct dma_fence *fence)
+{
+	return __i915_timeline_sync_set(tl, fence->context, fence->seqno);
+}
+
+static inline bool __i915_timeline_sync_is_later(struct i915_timeline *tl,
+						 u64 context, u32 seqno)
+{
+	return i915_syncmap_is_later(&tl->sync, context, seqno);
+}
+
+static inline bool i915_timeline_sync_is_later(struct i915_timeline *tl,
+					       const struct dma_fence *fence)
+{
+	return __i915_timeline_sync_is_later(tl, fence->context, fence->seqno);
+}
+
+void i915_timelines_park(struct drm_i915_private *i915);
+
+#endif