drm/i915: Squash repeated awaits on the same fence

Track the latest fence waited upon on each context, and only add a new
asynchronous wait if the new fence is more recent than the recorded
fence for that context. This requires us to filter out unordered
timelines, which are noted by DMA_FENCE_NO_CONTEXT. However, in the
absence of a universal identifier, we have to use our own
i915->mm.unordered_timeline token.

v2: Throw around the debug crutches
v3: Inline the likely case of the pre-allocation cache being full.
v4: Drop the pre-allocation support, we can lose the most recent fence
in case of allocation failure -- it just means we may emit more awaits
than strictly necessary but will not break.
v5: Trim allocation size for leaf nodes, they only need an array of u32
not pointers.
v6: Create mock_timeline to tidy selftest writing
v7: s/intel_timeline_sync_get/intel_timeline_sync_is_later/ (Tvrtko)
v8: Prune the stale sync points when we idle.
v9: Include a small benchmark in the kselftests
v10: Separate the idr implementation into its own compartment. (Tvrkto)
v11: Refactor igt_sync kselftests to avoid deep nesting (Tvrkto)
v12: __sync_leaf_idx() to assert that p->height is 0 when checking leaves
v13: kselftests to investigate struct i915_syncmap itself (Tvrtko)
v14: Foray into ascii art graphs
v15: Take into account that the random lookup/insert does 2 prng calls,
not 1, when benchmarking, and use for_each_set_bit() (Tvrtko)
v16: Improved ascii art

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170503093924.5320-4-chris@chris-wilson.co.uk

15 files changed, 1588 insertions, 18 deletions

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index 2cf0450..7b05fb8 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -16,6 +16,7 @@ i915-y := i915_drv.o \
 	  i915_params.o \
 	  i915_pci.o \
           i915_suspend.o \
+	  i915_syncmap.o \
 	  i915_sw_fence.o \
 	  i915_sysfs.o \
 	  intel_csr.o \
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index e91590d..f9c6b9b 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3196,6 +3196,7 @@ i915_gem_idle_work_handler(struct work_struct *work)
 		intel_engine_disarm_breadcrumbs(engine);
 		i915_gem_batch_pool_fini(&engine->batch_pool);
 	}
+	i915_gem_timelines_mark_idle(dev_priv);
 
 	GEM_BUG_ON(!dev_priv->gt.awake);
 	dev_priv->gt.awake = false;
diff --git a/drivers/gpu/drm/i915/i915_gem.h b/drivers/gpu/drm/i915/i915_gem.h
index 5a49487..ee54597 100644
--- a/drivers/gpu/drm/i915/i915_gem.h
+++ b/drivers/gpu/drm/i915/i915_gem.h
@@ -25,6 +25,8 @@
 #ifndef __I915_GEM_H__
 #define __I915_GEM_H__
 
+#include <linux/bug.h>
+
 #ifdef CONFIG_DRM_I915_DEBUG_GEM
 #define GEM_BUG_ON(expr) BUG_ON(expr)
 #define GEM_WARN_ON(expr) WARN_ON(expr)
diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index 022f558..637b8cd 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -773,6 +773,11 @@ i915_gem_request_await_dma_fence(struct drm_i915_gem_request *req,
 		if (fence->context == req->fence.context)
 			continue;
 
+		/* Squash repeated waits to the same timelines */
+		if (fence->context != req->i915->mm.unordered_timeline &&
+		    intel_timeline_sync_is_later(req->timeline, fence))
+			continue;
+
 		if (dma_fence_is_i915(fence))
 			ret = i915_gem_request_await_request(req,
 							     to_request(fence));
@@ -782,6 +787,10 @@ i915_gem_request_await_dma_fence(struct drm_i915_gem_request *req,
 							    GFP_KERNEL);
 		if (ret < 0)
 			return ret;
+
+		/* Record the latest fence used against each timeline */
+		if (fence->context != req->i915->mm.unordered_timeline)
+			intel_timeline_sync_set(req->timeline, fence);
 	} while (--nchild);
 
 	return 0;
diff --git a/drivers/gpu/drm/i915/i915_gem_timeline.c b/drivers/gpu/drm/i915/i915_gem_timeline.c
index b596ca7..c597ce2 100644
--- a/drivers/gpu/drm/i915/i915_gem_timeline.c
+++ b/drivers/gpu/drm/i915/i915_gem_timeline.c
@@ -23,6 +23,32 @@
  */
 
 #include "i915_drv.h"
+#include "i915_syncmap.h"
+
+static void __intel_timeline_init(struct intel_timeline *tl,
+				  struct i915_gem_timeline *parent,
+				  u64 context,
+				  struct lock_class_key *lockclass,
+				  const char *lockname)
+{
+	tl->fence_context = context;
+	tl->common = parent;
+#ifdef CONFIG_DEBUG_SPINLOCK
+	__raw_spin_lock_init(&tl->lock.rlock, lockname, lockclass);
+#else
+	spin_lock_init(&tl->lock);
+#endif
+	init_request_active(&tl->last_request, NULL);
+	INIT_LIST_HEAD(&tl->requests);
+	i915_syncmap_init(&tl->sync);
+}
+
+static void __intel_timeline_fini(struct intel_timeline *tl)
+{
+	GEM_BUG_ON(!list_empty(&tl->requests));
+
+	i915_syncmap_free(&tl->sync);
+}
 
 static int __i915_gem_timeline_init(struct drm_i915_private *i915,
 				    struct i915_gem_timeline *timeline,
@@ -35,6 +61,14 @@ static int __i915_gem_timeline_init(struct drm_i915_private *i915,
 
 	lockdep_assert_held(&i915->drm.struct_mutex);
 
+	/*
+	 * Ideally we want a set of engines on a single leaf as we expect
+	 * to mostly be tracking synchronisation between engines. It is not
+	 * a huge issue if this is not the case, but we may want to mitigate
+	 * any page crossing penalties if they become an issue.
+	 */
+	BUILD_BUG_ON(KSYNCMAP < I915_NUM_ENGINES);
+
 	timeline->i915 = i915;
 	timeline->name = kstrdup(name ?: "[kernel]", GFP_KERNEL);
 	if (!timeline->name)
@@ -44,19 +78,10 @@ static int __i915_gem_timeline_init(struct drm_i915_private *i915,
 
 	/* Called during early_init before we know how many engines there are */
 	fences = dma_fence_context_alloc(ARRAY_SIZE(timeline->engine));
-	for (i = 0; i < ARRAY_SIZE(timeline->engine); i++) {
-		struct intel_timeline *tl = &timeline->engine[i];
-
-		tl->fence_context = fences++;
-		tl->common = timeline;
-#ifdef CONFIG_DEBUG_SPINLOCK
-		__raw_spin_lock_init(&tl->lock.rlock, lockname, lockclass);
-#else
-		spin_lock_init(&tl->lock);
-#endif
-		init_request_active(&tl->last_request, NULL);
-		INIT_LIST_HEAD(&tl->requests);
-	}
+	for (i = 0; i < ARRAY_SIZE(timeline->engine); i++)
+		__intel_timeline_init(&timeline->engine[i],
+				      timeline, fences++,
+				      lockclass, lockname);
 
 	return 0;
 }
@@ -81,18 +106,52 @@ int i915_gem_timeline_init__global(struct drm_i915_private *i915)
 					&class, "&global_timeline->lock");
 }
 
+/**
+ * i915_gem_timelines_mark_idle -- called when the driver idles
+ * @i915 - the drm_i915_private device
+ *
+ * When the driver is completely idle, we know that all of our sync points
+ * have been signaled and our tracking is then entirely redundant. Any request
+ * to wait upon an older sync point will be completed instantly as we know
+ * the fence is signaled and therefore we will not even look them up in the
+ * sync point map.
+ */
+void i915_gem_timelines_mark_idle(struct drm_i915_private *i915)
+{
+	struct i915_gem_timeline *timeline;
+	int i;
+
+	lockdep_assert_held(&i915->drm.struct_mutex);
+
+	list_for_each_entry(timeline, &i915->gt.timelines, link) {
+		for (i = 0; i < ARRAY_SIZE(timeline->engine); i++) {
+			struct intel_timeline *tl = &timeline->engine[i];
+
+			/*
+			 * All known fences are completed so we can scrap
+			 * the current sync point tracking and start afresh,
+			 * any attempt to wait upon a previous sync point
+			 * will be skipped as the fence was signaled.
+			 */
+			i915_syncmap_free(&tl->sync);
+		}
+	}
+}
+
 void i915_gem_timeline_fini(struct i915_gem_timeline *timeline)
 {
 	int i;
 
 	lockdep_assert_held(&timeline->i915->drm.struct_mutex);
 
-	for (i = 0; i < ARRAY_SIZE(timeline->engine); i++) {
-		struct intel_timeline *tl = &timeline->engine[i];
-
-		GEM_BUG_ON(!list_empty(&tl->requests));
-	}
+	for (i = 0; i < ARRAY_SIZE(timeline->engine); i++)
+		__intel_timeline_fini(&timeline->engine[i]);
 
 	list_del(&timeline->link);
 	kfree(timeline->name);
 }
+
+#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
+#include "selftests/mock_timeline.c"
+#include "selftests/i915_gem_timeline.c"
+#endif
diff --git a/drivers/gpu/drm/i915/i915_gem_timeline.h b/drivers/gpu/drm/i915/i915_gem_timeline.h
index 6c53e14..ff65c64 100644
--- a/drivers/gpu/drm/i915/i915_gem_timeline.h
+++ b/drivers/gpu/drm/i915/i915_gem_timeline.h
@@ -27,7 +27,9 @@
 
 #include <linux/list.h>
 
+#include "i915_utils.h"
 #include "i915_gem_request.h"
+#include "i915_syncmap.h"
 
 struct i915_gem_timeline;
 
@@ -55,6 +57,17 @@ struct intel_timeline {
 	 * 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;
 	u32 sync_seqno[I915_NUM_ENGINES];
 
 	struct i915_gem_timeline *common;
@@ -73,6 +86,31 @@ int i915_gem_timeline_init(struct drm_i915_private *i915,
 			   struct i915_gem_timeline *tl,
 			   const char *name);
 int i915_gem_timeline_init__global(struct drm_i915_private *i915);
+void i915_gem_timelines_mark_idle(struct drm_i915_private *i915);
 void i915_gem_timeline_fini(struct i915_gem_timeline *tl);
 
+static inline int __intel_timeline_sync_set(struct intel_timeline *tl,
+					    u64 context, u32 seqno)
+{
+	return i915_syncmap_set(&tl->sync, context, seqno);
+}
+
+static inline int intel_timeline_sync_set(struct intel_timeline *tl,
+					  const struct dma_fence *fence)
+{
+	return __intel_timeline_sync_set(tl, fence->context, fence->seqno);
+}
+
+static inline bool __intel_timeline_sync_is_later(struct intel_timeline *tl,
+						  u64 context, u32 seqno)
+{
+	return i915_syncmap_is_later(&tl->sync, context, seqno);
+}
+
+static inline bool intel_timeline_sync_is_later(struct intel_timeline *tl,
+						const struct dma_fence *fence)
+{
+	return __intel_timeline_sync_is_later(tl, fence->context, fence->seqno);
+}
+
 #endif
diff --git a/drivers/gpu/drm/i915/i915_syncmap.c b/drivers/gpu/drm/i915/i915_syncmap.c
new file mode 100644
index 0000000..0087acf
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_syncmap.c
@@ -0,0 +1,412 @@
+/*
+ * Copyright © 2017 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.
+ *
+ */
+
+#include <linux/slab.h>
+
+#include "i915_syncmap.h"
+
+#include "i915_gem.h" /* GEM_BUG_ON() */
+#include "i915_selftest.h"
+
+#define SHIFT ilog2(KSYNCMAP)
+#define MASK (KSYNCMAP - 1)
+
+/*
+ * struct i915_syncmap is a layer of a radixtree that maps a u64 fence
+ * context id to the last u32 fence seqno waited upon from that context.
+ * Unlike lib/radixtree it uses a parent pointer that allows traversal back to
+ * the root. This allows us to access the whole tree via a single pointer
+ * to the most recently used layer. We expect fence contexts to be dense
+ * and most reuse to be on the same i915_gem_context but on neighbouring
+ * engines (i.e. on adjacent contexts) and reuse the same leaf, a very
+ * effective lookup cache. If the new lookup is not on the same leaf, we
+ * expect it to be on the neighbouring branch.
+ *
+ * A leaf holds an array of u32 seqno, and has height 0. The bitmap field
+ * allows us to store whether a particular seqno is valid (i.e. allows us
+ * to distinguish unset from 0).
+ *
+ * A branch holds an array of layer pointers, and has height > 0, and always
+ * has at least 2 layers (either branches or leaves) below it.
+ *
+ * For example,
+ *	for x in
+ *	  0 1 2 0x10 0x11 0x200 0x201
+ *	  0x500000 0x500001 0x503000 0x503001
+ *	  0xE<<60:
+ *		i915_syncmap_set(&sync, x, lower_32_bits(x));
+ * will build a tree like:
+ *	0xXXXXXXXXXXXXXXXX
+ *	0-> 0x0000000000XXXXXX
+ *	|   0-> 0x0000000000000XXX
+ *	|   |   0-> 0x00000000000000XX
+ *	|   |   |   0-> 0x000000000000000X 0:0, 1:1, 2:2
+ *	|   |   |   1-> 0x000000000000001X 0:10, 1:11
+ *	|   |   2-> 0x000000000000020X 0:200, 1:201
+ *	|   5-> 0x000000000050XXXX
+ *	|       0-> 0x000000000050000X 0:500000, 1:500001
+ *	|       3-> 0x000000000050300X 0:503000, 1:503001
+ *	e-> 0xe00000000000000X e:e
+ */
+
+struct i915_syncmap {
+	u64 prefix;
+	unsigned int height;
+	unsigned int bitmap;
+	struct i915_syncmap *parent;
+	/*
+	 * Following this header is an array of either seqno or child pointers:
+	 * union {
+	 *	u32 seqno[KSYNCMAP];
+	 *	struct i915_syncmap *child[KSYNCMAP];
+	 * };
+	 */
+};
+
+/**
+ * i915_syncmap_init -- initialise the #i915_syncmap
+ * @root - pointer to the #i915_syncmap
+ */
+void i915_syncmap_init(struct i915_syncmap **root)
+{
+	BUILD_BUG_ON_NOT_POWER_OF_2(KSYNCMAP);
+	BUILD_BUG_ON_NOT_POWER_OF_2(SHIFT);
+	BUILD_BUG_ON(KSYNCMAP > BITS_PER_BYTE * sizeof((*root)->bitmap));
+	*root = NULL;
+}
+
+static inline u32 *__sync_seqno(struct i915_syncmap *p)
+{
+	GEM_BUG_ON(p->height);
+	return (u32 *)(p + 1);
+}
+
+static inline struct i915_syncmap **__sync_child(struct i915_syncmap *p)
+{
+	GEM_BUG_ON(!p->height);
+	return (struct i915_syncmap **)(p + 1);
+}
+
+static inline unsigned int
+__sync_branch_idx(const struct i915_syncmap *p, u64 id)
+{
+	return (id >> p->height) & MASK;
+}
+
+static inline unsigned int
+__sync_leaf_idx(const struct i915_syncmap *p, u64 id)
+{
+	GEM_BUG_ON(p->height);
+	return id & MASK;
+}
+
+static inline u64 __sync_branch_prefix(const struct i915_syncmap *p, u64 id)
+{
+	return id >> p->height >> SHIFT;
+}
+
+static inline u64 __sync_leaf_prefix(const struct i915_syncmap *p, u64 id)
+{
+	GEM_BUG_ON(p->height);
+	return id >> SHIFT;
+}
+
+static inline bool seqno_later(u32 a, u32 b)
+{
+	return (s32)(a - b) >= 0;
+}
+
+/**
+ * i915_syncmap_is_later -- compare against the last know sync point
+ * @root - pointer to the #i915_syncmap
+ * @id - the context id (other timeline) we are synchronising to
+ * @seqno - the sequence number along the other timeline
+ *
+ * If we have already synchronised this @root timeline with another (@id) then
+ * we can omit any repeated or earlier synchronisation requests. If the two
+ * timelines are already coupled, we can also omit the dependency between the
+ * two as that is already known via the timeline.
+ *
+ * Returns true if the two timelines are already synchronised wrt to @seqno,
+ * false if not and the synchronisation must be emitted.
+ */
+bool i915_syncmap_is_later(struct i915_syncmap **root, u64 id, u32 seqno)
+{
+	struct i915_syncmap *p;
+	unsigned int idx;
+
+	p = *root;
+	if (!p)
+		return false;
+
+	if (likely(__sync_leaf_prefix(p, id) == p->prefix))
+		goto found;
+
+	/* First climb the tree back to a parent branch */
+	do {
+		p = p->parent;
+		if (!p)
+			return false;
+
+		if (__sync_branch_prefix(p, id) == p->prefix)
+			break;
+	} while (1);
+
+	/* And then descend again until we find our leaf */
+	do {
+		if (!p->height)
+			break;
+
+		p = __sync_child(p)[__sync_branch_idx(p, id)];
+		if (!p)
+			return false;
+
+		if (__sync_branch_prefix(p, id) != p->prefix)
+			return false;
+	} while (1);
+
+	*root = p;
+found:
+	idx = __sync_leaf_idx(p, id);
+	if (!(p->bitmap & BIT(idx)))
+		return false;
+
+	return seqno_later(__sync_seqno(p)[idx], seqno);
+}
+
+static struct i915_syncmap *
+__sync_alloc_leaf(struct i915_syncmap *parent, u64 id)
+{
+	struct i915_syncmap *p;
+
+	p = kmalloc(sizeof(*p) + KSYNCMAP * sizeof(u32), GFP_KERNEL);
+	if (unlikely(!p))
+		return NULL;
+
+	p->parent = parent;
+	p->height = 0;
+	p->bitmap = 0;
+	p->prefix = __sync_leaf_prefix(p, id);
+	return p;
+}
+
+static inline void __sync_set_seqno(struct i915_syncmap *p, u64 id, u32 seqno)
+{
+	unsigned int idx = __sync_leaf_idx(p, id);
+
+	p->bitmap |= BIT(idx);
+	__sync_seqno(p)[idx] = seqno;
+}
+
+static inline void __sync_set_child(struct i915_syncmap *p,
+				    unsigned int idx,
+				    struct i915_syncmap *child)
+{
+	p->bitmap |= BIT(idx);
+	__sync_child(p)[idx] = child;
+}
+
+static noinline int __sync_set(struct i915_syncmap **root, u64 id, u32 seqno)
+{
+	struct i915_syncmap *p = *root;
+	unsigned int idx;
+
+	if (!p) {
+		p = __sync_alloc_leaf(NULL, id);
+		if (unlikely(!p))
+			return -ENOMEM;
+
+		goto found;
+	}
+
+	/* Caller handled the likely cached case */
+	GEM_BUG_ON(__sync_leaf_prefix(p, id) == p->prefix);
+
+	/* Climb back up the tree until we find a common prefix */
+	do {
+		if (!p->parent)
+			break;
+
+		p = p->parent;
+
+		if (__sync_branch_prefix(p, id) == p->prefix)
+			break;
+	} while (1);
+
+	/*
+	 * No shortcut, we have to descend the tree to find the right layer
+	 * containing this fence.
+	 *
+	 * Each layer in the tree holds 16 (KSYNCMAP) pointers, either fences
+	 * or lower layers. Leaf nodes (height = 0) contain the fences, all
+	 * other nodes (height > 0) are internal layers that point to a lower
+	 * node. Each internal layer has at least 2 descendents.
+	 *
+	 * Starting at the top, we check whether the current prefix matches. If
+	 * it doesn't, we have gone past our target and need to insert a join
+	 * into the tree, and a new leaf node for the target as a descendent
+	 * of the join, as well as the original layer.
+	 *
+	 * The matching prefix means we are still following the right branch
+	 * of the tree. If it has height 0, we have found our leaf and just
+	 * need to replace the fence slot with ourselves. If the height is
+	 * not zero, our slot contains the next layer in the tree (unless
+	 * it is empty, in which case we can add ourselves as a new leaf).
+	 * As descend the tree the prefix grows (and height decreases).
+	 */
+	do {
+		struct i915_syncmap *next;
+
+		if (__sync_branch_prefix(p, id) != p->prefix) {
+			unsigned int above;
+
+			/* Insert a join above the current layer */
+			next = kzalloc(sizeof(*next) + KSYNCMAP * sizeof(next),
+				       GFP_KERNEL);
+			if (unlikely(!next))
+				return -ENOMEM;
+
+			/* Compute the height at which these two diverge */
+			above = fls64(__sync_branch_prefix(p, id) ^ p->prefix);
+			above = round_up(above, SHIFT);
+			next->height = above + p->height;
+			next->prefix = __sync_branch_prefix(next, id);
+
+			/* Insert the join into the parent */
+			if (p->parent) {
+				idx = __sync_branch_idx(p->parent, id);
+				__sync_child(p->parent)[idx] = next;
+				GEM_BUG_ON(!(p->parent->bitmap & BIT(idx)));
+			}
+			next->parent = p->parent;
+
+			/* Compute the idx of the other branch, not our id! */
+			idx = p->prefix >> (above - SHIFT) & MASK;
+			__sync_set_child(next, idx, p);
+			p->parent = next;
+
+			/* Ascend to the join */
+			p = next;
+		} else {
+			if (!p->height)
+				break;
+		}
+
+		/* Descend into the next layer */
+		GEM_BUG_ON(!p->height);
+		idx = __sync_branch_idx(p, id);
+		next = __sync_child(p)[idx];
+		if (!next) {
+			next = __sync_alloc_leaf(p, id);
+			if (unlikely(!next))
+				return -ENOMEM;
+
+			__sync_set_child(p, idx, next);
+			p = next;
+			break;
+		}
+
+		p = next;
+	} while (1);
+
+found:
+	GEM_BUG_ON(p->prefix != __sync_leaf_prefix(p, id));
+	__sync_set_seqno(p, id, seqno);
+	*root = p;
+	return 0;
+}
+
+/**
+ * i915_syncmap_set -- mark the most recent syncpoint between contexts
+ * @root - pointer to the #i915_syncmap
+ * @id - the context id (other timeline) we have synchronised to
+ * @seqno - the sequence number along the other timeline
+ *
+ * When we synchronise this @root timeline with another (@id), we also know
+ * that we have synchronized with all previous seqno along that timeline. If
+ * we then have a request to synchronise with the same seqno or older, we can
+ * omit it, see i915_syncmap_is_later()
+ *
+ * Returns 0 on success, or a negative error code.
+ */
+int i915_syncmap_set(struct i915_syncmap **root, u64 id, u32 seqno)
+{
+	struct i915_syncmap *p = *root;
+
+	/*
+	 * We expect to be called in sequence following is_later(id), which
+	 * should have preloaded the root for us.
+	 */
+	if (likely(p && __sync_leaf_prefix(p, id) == p->prefix)) {
+		__sync_set_seqno(p, id, seqno);
+		return 0;
+	}
+
+	return __sync_set(root, id, seqno);
+}
+
+static void __sync_free(struct i915_syncmap *p)
+{
+	if (p->height) {
+		unsigned int i;
+
+		while ((i = ffs(p->bitmap))) {
+			p->bitmap &= ~0u << i;
+			__sync_free(__sync_child(p)[i - 1]);
+		}
+	}
+
+	kfree(p);
+}
+
+/**
+ * i915_syncmap_free -- free all memory associated with the syncmap
+ * @root - pointer to the #i915_syncmap
+ *
+ * Either when the timeline is to be freed and we no longer need the sync
+ * point tracking, or when the fences are all known to be signaled and the
+ * sync point tracking is redundant, we can free the #i915_syncmap to recover
+ * its allocations.
+ *
+ * Will reinitialise the @root pointer so that the #i915_syncmap is ready for
+ * reuse.
+ */
+void i915_syncmap_free(struct i915_syncmap **root)
+{
+	struct i915_syncmap *p;
+
+	p = *root;
+	if (!p)
+		return;
+
+	while (p->parent)
+		p = p->parent;
+
+	__sync_free(p);
+	*root = NULL;
+}
+
+#if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
+#include "selftests/i915_syncmap.c"
+#endif
diff --git a/drivers/gpu/drm/i915/i915_syncmap.h b/drivers/gpu/drm/i915/i915_syncmap.h
new file mode 100644
index 0000000..0653f70
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_syncmap.h
@@ -0,0 +1,38 @@
+/*
+ * Copyright © 2017 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_SYNCMAP_H__
+#define __I915_SYNCMAP_H__
+
+#include <linux/types.h>
+
+struct i915_syncmap;
+#define KSYNCMAP 16 /* radix of the tree, how many slots in each layer */
+
+void i915_syncmap_init(struct i915_syncmap **root);
+int i915_syncmap_set(struct i915_syncmap **root, u64 id, u32 seqno);
+bool i915_syncmap_is_later(struct i915_syncmap **root, u64 id, u32 seqno);
+void i915_syncmap_free(struct i915_syncmap **root);
+
+#endif /* __I915_SYNCMAP_H__ */
diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_timeline.c b/drivers/gpu/drm/i915/selftests/i915_gem_timeline.c
new file mode 100644
index 0000000..6df00cc
--- /dev/null
+++ b/drivers/gpu/drm/i915/selftests/i915_gem_timeline.c
@@ -0,0 +1,301 @@
+/*
+ * Copyright © 2017 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.
+ *
+ */
+
+#include "../i915_selftest.h"
+#include "i915_random.h"
+
+#include "mock_gem_device.h"
+#include "mock_timeline.h"
+
+struct __igt_sync {
+	const char *name;
+	u32 seqno;
+	bool expected;
+	bool set;
+};
+
+static int __igt_sync(struct intel_timeline *tl,
+		      u64 ctx,
+		      const struct __igt_sync *p,
+		      const char *name)
+{
+	int ret;
+
+	if (__intel_timeline_sync_is_later(tl, ctx, p->seqno) != p->expected) {
+		pr_err("%s: %s(ctx=%llu, seqno=%u) expected passed %s but failed\n",
+		       name, p->name, ctx, p->seqno, yesno(p->expected));
+		return -EINVAL;
+	}
+
+	if (p->set) {
+		ret = __intel_timeline_sync_set(tl, ctx, p->seqno);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int igt_sync(void *arg)
+{
+	const struct __igt_sync pass[] = {
+		{ "unset", 0, false, false },
+		{ "new", 0, false, true },
+		{ "0a", 0, true, true },
+		{ "1a", 1, false, true },
+		{ "1b", 1, true, true },
+		{ "0b", 0, true, false },
+		{ "2a", 2, false, true },
+		{ "4", 4, false, true },
+		{ "INT_MAX", INT_MAX, false, true },
+		{ "INT_MAX-1", INT_MAX-1, true, false },
+		{ "INT_MAX+1", (u32)INT_MAX+1, false, true },
+		{ "INT_MAX", INT_MAX, true, false },
+		{ "UINT_MAX", UINT_MAX, false, true },
+		{ "wrap", 0, false, true },
+		{ "unwrap", UINT_MAX, true, false },
+		{},
+	}, *p;
+	struct intel_timeline *tl;
+	int order, offset;
+	int ret;
+
+	tl = mock_timeline(0);
+	if (!tl)
+		return -ENOMEM;
+
+	for (p = pass; p->name; p++) {
+		for (order = 1; order < 64; order++) {
+			for (offset = -1; offset <= (order > 1); offset++) {
+				u64 ctx = BIT_ULL(order) + offset;
+
+				ret = __igt_sync(tl, ctx, p, "1");
+				if (ret)
+					goto out;
+			}
+		}
+	}
+	mock_timeline_destroy(tl);
+
+	tl = mock_timeline(0);
+	if (!tl)
+		return -ENOMEM;
+
+	for (order = 1; order < 64; order++) {
+		for (offset = -1; offset <= (order > 1); offset++) {
+			u64 ctx = BIT_ULL(order) + offset;
+
+			for (p = pass; p->name; p++) {
+				ret = __igt_sync(tl, ctx, p, "2");
+				if (ret)
+					goto out;
+			}
+		}
+	}
+
+out:
+	mock_timeline_destroy(tl);
+	return ret;
+}
+
+static unsigned int random_engine(struct rnd_state *rnd)
+{
+	return ((u64)prandom_u32_state(rnd) * I915_NUM_ENGINES) >> 32;
+}
+
+static int bench_sync(void *arg)
+{
+#define M (1 << 20)
+	struct rnd_state prng;
+	struct intel_timeline *tl;
+	unsigned long end_time, count;
+	u64 prng32_1M;
+	ktime_t kt;
+	int order, last_order;
+
+	tl = mock_timeline(0);
+	if (!tl)
+		return -ENOMEM;
+
+	/* Lookups from cache are very fast and so the random number generation
+	 * and the loop itself becomes a significant factor in the per-iteration
+	 * timings. We try to compensate the results by measuring the overhead
+	 * of the prng and subtract it from the reported results.
+	 */
+	prandom_seed_state(&prng, i915_selftest.random_seed);
+	count = 0;
+	kt = ktime_get();
+	end_time = jiffies + HZ/10;
+	do {
+		u32 x;
+
+		/* Make sure the compiler doesn't optimise away the prng call */
+		WRITE_ONCE(x, prandom_u32_state(&prng));
+
+		count++;
+	} while (!time_after(jiffies, end_time));
+	kt = ktime_sub(ktime_get(), kt);
+	pr_debug("%s: %lu random evaluations, %lluns/prng\n",
+		 __func__, count, (long long)div64_ul(ktime_to_ns(kt), count));
+	prng32_1M = ktime_to_ns(kt) * M / count;
+
+	/* Benchmark (only) setting random context ids */
+	prandom_seed_state(&prng, i915_selftest.random_seed);
+	count = 0;
+	kt = ktime_get();
+	end_time = jiffies + HZ/10;
+	do {
+		u64 id = i915_prandom_u64_state(&prng);
+
+		__intel_timeline_sync_set(tl, id, 0);
+		count++;
+	} while (!time_after(jiffies, end_time));
+	kt = ktime_sub(ktime_get(), kt);
+	kt = ktime_sub_ns(kt, count * prng32_1M * 2 / M);
+	pr_info("%s: %lu random insertions, %lluns/insert\n",
+		__func__, count, (long long)div64_ul(ktime_to_ns(kt), count));
+
+	/* Benchmark looking up the exact same context ids as we just set */
+	prandom_seed_state(&prng, i915_selftest.random_seed);
+	end_time = count;
+	kt = ktime_get();
+	while (end_time--) {
+		u64 id = i915_prandom_u64_state(&prng);
+
+		if (!__intel_timeline_sync_is_later(tl, id, 0)) {
+			mock_timeline_destroy(tl);
+			pr_err("Lookup of %llu failed\n", id);
+			return -EINVAL;
+		}
+	}
+	kt = ktime_sub(ktime_get(), kt);
+	kt = ktime_sub_ns(kt, count * prng32_1M * 2 / M);
+	pr_info("%s: %lu random lookups, %lluns/lookup\n",
+		__func__, count, (long long)div64_ul(ktime_to_ns(kt), count));
+
+	mock_timeline_destroy(tl);
+	cond_resched();
+
+	tl = mock_timeline(0);
+	if (!tl)
+		return -ENOMEM;
+
+	/* Benchmark setting the first N (in order) contexts */
+	count = 0;
+	kt = ktime_get();
+	end_time = jiffies + HZ/10;
+	do {
+		__intel_timeline_sync_set(tl, count++, 0);
+	} while (!time_after(jiffies, end_time));
+	kt = ktime_sub(ktime_get(), kt);
+	pr_info("%s: %lu in-order insertions, %lluns/insert\n",
+		__func__, count, (long long)div64_ul(ktime_to_ns(kt), count));
+
+	/* Benchmark looking up the exact same context ids as we just set */
+	end_time = count;
+	kt = ktime_get();
+	while (end_time--) {
+		if (!__intel_timeline_sync_is_later(tl, end_time, 0)) {
+			pr_err("Lookup of %lu failed\n", end_time);
+			mock_timeline_destroy(tl);
+			return -EINVAL;
+		}
+	}
+	kt = ktime_sub(ktime_get(), kt);
+	pr_info("%s: %lu in-order lookups, %lluns/lookup\n",
+		__func__, count, (long long)div64_ul(ktime_to_ns(kt), count));
+
+	mock_timeline_destroy(tl);
+	cond_resched();
+
+	tl = mock_timeline(0);
+	if (!tl)
+		return -ENOMEM;
+
+	/* Benchmark searching for a random context id and maybe changing it */
+	prandom_seed_state(&prng, i915_selftest.random_seed);
+	count = 0;
+	kt = ktime_get();
+	end_time = jiffies + HZ/10;
+	do {
+		u32 id = random_engine(&prng);
+		u32 seqno = prandom_u32_state(&prng);
+
+		if (!__intel_timeline_sync_is_later(tl, id, seqno))
+			__intel_timeline_sync_set(tl, id, seqno);
+
+		count++;
+	} while (!time_after(jiffies, end_time));
+	kt = ktime_sub(ktime_get(), kt);
+	kt = ktime_sub_ns(kt, count * prng32_1M * 2 / M);
+	pr_info("%s: %lu repeated insert/lookups, %lluns/op\n",
+		__func__, count, (long long)div64_ul(ktime_to_ns(kt), count));
+	mock_timeline_destroy(tl);
+	cond_resched();
+
+	/* Benchmark searching for a known context id and changing the seqno */
+	for (last_order = 1, order = 1; order < 32;
+	     ({ int tmp = last_order; last_order = order; order += tmp; })) {
+		unsigned int mask = BIT(order) - 1;
+
+		tl = mock_timeline(0);
+		if (!tl)
+			return -ENOMEM;
+
+		count = 0;
+		kt = ktime_get();
+		end_time = jiffies + HZ/10;
+		do {
+			/* Without assuming too many details of the underlying
+			 * implementation, try to identify its phase-changes
+			 * (if any)!
+			 */
+			u64 id = (u64)(count & mask) << order;
+
+			__intel_timeline_sync_is_later(tl, id, 0);
+			__intel_timeline_sync_set(tl, id, 0);
+
+			count++;
+		} while (!time_after(jiffies, end_time));
+		kt = ktime_sub(ktime_get(), kt);
+		pr_info("%s: %lu cyclic/%d insert/lookups, %lluns/op\n",
+			__func__, count, order,
+			(long long)div64_ul(ktime_to_ns(kt), count));
+		mock_timeline_destroy(tl);
+		cond_resched();
+	}
+
+	return 0;
+#undef M
+}
+
+int i915_gem_timeline_mock_selftests(void)
+{
+	static const struct i915_subtest tests[] = {
+		SUBTEST(igt_sync),
+		SUBTEST(bench_sync),
+	};
+
+	return i915_subtests(tests, NULL);
+}
diff --git a/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h b/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
index be9a9eb..76c1f14 100644
--- a/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
+++ b/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
@@ -10,8 +10,10 @@
  */
 selftest(sanitycheck, i915_mock_sanitycheck) /* keep first (igt selfcheck) */
 selftest(scatterlist, scatterlist_mock_selftests)
+selftest(syncmap, i915_syncmap_mock_selftests)
 selftest(uncore, intel_uncore_mock_selftests)
 selftest(breadcrumbs, intel_breadcrumbs_mock_selftests)
+selftest(timelines, i915_gem_timeline_mock_selftests)
 selftest(requests, i915_gem_request_mock_selftests)
 selftest(objects, i915_gem_object_mock_selftests)
 selftest(dmabuf, i915_gem_dmabuf_mock_selftests)
diff --git a/drivers/gpu/drm/i915/selftests/i915_random.c b/drivers/gpu/drm/i915/selftests/i915_random.c
index c17c83c..d044bf9 100644
--- a/drivers/gpu/drm/i915/selftests/i915_random.c
+++ b/drivers/gpu/drm/i915/selftests/i915_random.c
@@ -30,6 +30,17 @@
 
 #include "i915_random.h"
 
+u64 i915_prandom_u64_state(struct rnd_state *rnd)
+{
+	u64 x;
+
+	x = prandom_u32_state(rnd);
+	x <<= 32;
+	x |= prandom_u32_state(rnd);
+
+	return x;
+}
+
 static inline u32 i915_prandom_u32_max_state(u32 ep_ro, struct rnd_state *state)
 {
 	return upper_32_bits((u64)prandom_u32_state(state) * ep_ro);
diff --git a/drivers/gpu/drm/i915/selftests/i915_random.h b/drivers/gpu/drm/i915/selftests/i915_random.h
index b9c334c..6c93798 100644
--- a/drivers/gpu/drm/i915/selftests/i915_random.h
+++ b/drivers/gpu/drm/i915/selftests/i915_random.h
@@ -41,6 +41,8 @@
 #define I915_RND_SUBSTATE(name__, parent__) \
 	struct rnd_state name__ = I915_RND_STATE_INITIALIZER(prandom_u32_state(&(parent__)))
 
+u64 i915_prandom_u64_state(struct rnd_state *rnd);
+
 unsigned int *i915_random_order(unsigned int count,
 				struct rnd_state *state);
 void i915_random_reorder(unsigned int *order,
diff --git a/drivers/gpu/drm/i915/selftests/i915_syncmap.c b/drivers/gpu/drm/i915/selftests/i915_syncmap.c
new file mode 100644
index 0000000..bcab3d0
--- /dev/null
+++ b/drivers/gpu/drm/i915/selftests/i915_syncmap.c
@@ -0,0 +1,616 @@
+/*
+ * Copyright © 2017 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.
+ *
+ */
+
+#include "../i915_selftest.h"
+#include "i915_random.h"
+
+static char *
+__sync_print(struct i915_syncmap *p,
+	     char *buf, unsigned long *sz,
+	     unsigned int depth,
+	     unsigned int last,
+	     unsigned int idx)
+{
+	unsigned long len;
+	unsigned int i, X;
+
+	if (depth) {
+		unsigned int d;
+
+		for (d = 0; d < depth - 1; d++) {
+			if (last & BIT(depth - d - 1))
+				len = scnprintf(buf, *sz, "|   ");
+			else
+				len = scnprintf(buf, *sz, "    ");
+			buf += len;
+			*sz -= len;
+		}
+		len = scnprintf(buf, *sz, "%x-> ", idx);
+		buf += len;
+		*sz -= len;
+	}
+
+	/* We mark bits after the prefix as "X" */
+	len = scnprintf(buf, *sz, "0x%016llx", p->prefix << p->height << SHIFT);
+	buf += len;
+	*sz -= len;
+	X = (p->height + SHIFT) / 4;
+	scnprintf(buf - X, *sz + X, "%*s", X, "XXXXXXXXXXXXXXXXX");
+
+	if (!p->height) {
+		for_each_set_bit(i, (unsigned long *)&p->bitmap, KSYNCMAP) {
+			len = scnprintf(buf, *sz, " %x:%x,",
+					i, __sync_seqno(p)[i]);
+			buf += len;
+			*sz -= len;
+		}
+		buf -= 1;
+		*sz += 1;
+	}
+
+	len = scnprintf(buf, *sz, "\n");
+	buf += len;
+	*sz -= len;
+
+	if (p->height) {
+		for_each_set_bit(i, (unsigned long *)&p->bitmap, KSYNCMAP) {
+			buf = __sync_print(__sync_child(p)[i], buf, sz,
+					   depth + 1,
+					   last << 1 | !!(p->bitmap >> (i + 1)),
+					   i);
+		}
+	}
+
+	return buf;
+}
+
+static bool
+i915_syncmap_print_to_buf(struct i915_syncmap *p, char *buf, unsigned long sz)
+{
+	if (!p)
+		return false;
+
+	while (p->parent)
+		p = p->parent;
+
+	__sync_print(p, buf, &sz, 0, 1, 0);
+	return true;
+}
+
+static int check_syncmap_free(struct i915_syncmap **sync)
+{
+	i915_syncmap_free(sync);
+	if (*sync) {
+		pr_err("sync not cleared after free\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int dump_syncmap(struct i915_syncmap *sync, int err)
+{
+	char *buf;
+
+	if (!err)
+		return check_syncmap_free(&sync);
+
+	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!buf)
+		goto skip;
+
+	if (i915_syncmap_print_to_buf(sync, buf, PAGE_SIZE))
+		pr_err("%s", buf);
+
+	kfree(buf);
+
+skip:
+	i915_syncmap_free(&sync);
+	return err;
+}
+
+static int igt_syncmap_init(void *arg)
+{
+	struct i915_syncmap *sync = (void *)~0ul;
+
+	/*
+	 * Cursory check that we can initialise a random pointer and transform
+	 * it into the root pointer of a syncmap.
+	 */
+
+	i915_syncmap_init(&sync);
+	return check_syncmap_free(&sync);
+}
+
+static int check_seqno(struct i915_syncmap *leaf, unsigned int idx, u32 seqno)
+{
+	if (leaf->height) {
+		pr_err("%s: not a leaf, height is %d\n",
+		       __func__, leaf->height);
+		return -EINVAL;
+	}
+
+	if (__sync_seqno(leaf)[idx] != seqno) {
+		pr_err("%s: seqno[%d], found %x, expected %x\n",
+		       __func__, idx, __sync_seqno(leaf)[idx], seqno);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int check_one(struct i915_syncmap **sync, u64 context, u32 seqno)
+{
+	int err;
+
+	err = i915_syncmap_set(sync, context, seqno);
+	if (err)
+		return err;
+
+	if ((*sync)->height) {
+		pr_err("Inserting first context=%llx did not return leaf (height=%d, prefix=%llx\n",
+		       context, (*sync)->height, (*sync)->prefix);
+		return -EINVAL;
+	}
+
+	if ((*sync)->parent) {
+		pr_err("Inserting first context=%llx created branches!\n",
+		       context);
+		return -EINVAL;
+	}
+
+	if (hweight32((*sync)->bitmap) != 1) {
+		pr_err("First bitmap does not contain a single entry, found %x (count=%d)!\n",
+		       (*sync)->bitmap, hweight32((*sync)->bitmap));
+		return -EINVAL;
+	}
+
+	err = check_seqno((*sync), ilog2((*sync)->bitmap), seqno);
+	if (err)
+		return err;
+
+	if (!i915_syncmap_is_later(sync, context, seqno)) {
+		pr_err("Lookup of first context=%llx/seqno=%x failed!\n",
+		       context, seqno);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int igt_syncmap_one(void *arg)
+{
+	I915_RND_STATE(prng);
+	IGT_TIMEOUT(end_time);
+	struct i915_syncmap *sync;
+	unsigned long max = 1;
+	int err;
+
+	/*
+	 * Check that inserting a new id, creates a leaf and only that leaf.
+	 */
+
+	i915_syncmap_init(&sync);
+
+	do {
+		u64 context = i915_prandom_u64_state(&prng);
+		unsigned long loop;
+
+		err = check_syncmap_free(&sync);
+		if (err)
+			goto out;
+
+		for (loop = 0; loop <= max; loop++) {
+			err = check_one(&sync, context,
+					prandom_u32_state(&prng));
+			if (err)
+				goto out;
+		}
+		max++;
+	} while (!__igt_timeout(end_time, NULL));
+	pr_debug("%s: Completed %lu single insertions\n",
+		 __func__, max * (max - 1) / 2);
+out:
+	return dump_syncmap(sync, err);
+}
+
+static int check_leaf(struct i915_syncmap **sync, u64 context, u32 seqno)
+{
+	int err;
+
+	err = i915_syncmap_set(sync, context, seqno);
+	if (err)
+		return err;
+
+	if ((*sync)->height) {
+		pr_err("Inserting context=%llx did not return leaf (height=%d, prefix=%llx\n",
+		       context, (*sync)->height, (*sync)->prefix);
+		return -EINVAL;
+	}
+
+	if (hweight32((*sync)->bitmap) != 1) {
+		pr_err("First entry into leaf (context=%llx) does not contain a single entry, found %x (count=%d)!\n",
+		       context, (*sync)->bitmap, hweight32((*sync)->bitmap));
+		return -EINVAL;
+	}
+
+	err = check_seqno((*sync), ilog2((*sync)->bitmap), seqno);
+	if (err)
+		return err;
+
+	if (!i915_syncmap_is_later(sync, context, seqno)) {
+		pr_err("Lookup of first entry context=%llx/seqno=%x failed!\n",
+		       context, seqno);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int igt_syncmap_join_above(void *arg)
+{
+	struct i915_syncmap *sync;
+	unsigned int pass, order;
+	int err;
+
+	i915_syncmap_init(&sync);
+
+	/*
+	 * When we have a new id that doesn't fit inside the existing tree,
+	 * we need to add a new layer above.
+	 *
+	 * 1: 0x00000001
+	 * 2: 0x00000010
+	 * 3: 0x00000100
+	 * 4: 0x00001000
+	 * ...
+	 * Each pass the common prefix shrinks and we have to insert a join.
+	 * Each join will only contain two branches, the latest of which
+	 * is always a leaf.
+	 *
+	 * If we then reuse the same set of contexts, we expect to build an
+	 * identical tree.
+	 */
+	for (pass = 0; pass < 3; pass++) {
+		for (order = 0; order < 64; order += SHIFT) {
+			u64 context = BIT_ULL(order);
+			struct i915_syncmap *join;
+
+			err = check_leaf(&sync, context, 0);
+			if (err)
+				goto out;
+
+			join = sync->parent;
+			if (!join) /* very first insert will have no parents */
+				continue;
+
+			if (!join->height) {
+				pr_err("Parent with no height!\n");
+				err = -EINVAL;
+				goto out;
+			}
+
+			if (hweight32(join->bitmap) != 2) {
+				pr_err("Join does not have 2 children: %x (%d)\n",
+				       join->bitmap, hweight32(join->bitmap));
+				err = -EINVAL;
+				goto out;
+			}
+
+			if (__sync_child(join)[__sync_branch_idx(join, context)] != sync) {
+				pr_err("Leaf misplaced in parent!\n");
+				err = -EINVAL;
+				goto out;
+			}
+		}
+	}
+out:
+	return dump_syncmap(sync, err);
+}
+
+static int igt_syncmap_join_below(void *arg)
+{
+	struct i915_syncmap *sync;
+	unsigned int step, order, idx;
+	int err;
+
+	i915_syncmap_init(&sync);
+
+	/*
+	 * Check that we can split a compacted branch by replacing it with
+	 * a join.
+	 */
+	for (step = 0; step < KSYNCMAP; step++) {
+		for (order = 64 - SHIFT; order > 0; order -= SHIFT) {
+			u64 context = step * BIT_ULL(order);
+
+			err = i915_syncmap_set(&sync, context, 0);
+			if (err)
+				goto out;
+
+			if (sync->height) {
+				pr_err("Inserting context=%llx (order=%d, step=%d) did not return leaf (height=%d, prefix=%llx\n",
+				       context, order, step, sync->height, sync->prefix);
+				err = -EINVAL;
+				goto out;
+			}
+		}
+	}
+
+	for (step = 0; step < KSYNCMAP; step++) {
+		for (order = SHIFT; order < 64; order += SHIFT) {
+			u64 context = step * BIT_ULL(order);
+
+			if (!i915_syncmap_is_later(&sync, context, 0)) {
+				pr_err("1: context %llx (order=%d, step=%d) not found\n",
+				       context, order, step);
+				err = -EINVAL;
+				goto out;
+			}
+
+			for (idx = 1; idx < KSYNCMAP; idx++) {
+				if (i915_syncmap_is_later(&sync, context + idx, 0)) {
+					pr_err("1: context %llx (order=%d, step=%d) should not exist\n",
+					       context + idx, order, step);
+					err = -EINVAL;
+					goto out;
+				}
+			}
+		}
+	}
+
+	for (order = SHIFT; order < 64; order += SHIFT) {
+		for (step = 0; step < KSYNCMAP; step++) {
+			u64 context = step * BIT_ULL(order);
+
+			if (!i915_syncmap_is_later(&sync, context, 0)) {
+				pr_err("2: context %llx (order=%d, step=%d) not found\n",
+				       context, order, step);
+				err = -EINVAL;
+				goto out;
+			}
+		}
+	}
+
+out:
+	return dump_syncmap(sync, err);
+}
+
+static int igt_syncmap_neighbours(void *arg)
+{
+	I915_RND_STATE(prng);
+	IGT_TIMEOUT(end_time);
+	struct i915_syncmap *sync;
+	int err;
+
+	/*
+	 * Each leaf holds KSYNCMAP seqno. Check that when we create KSYNCMAP
+	 * neighbouring ids, they all fit into the same leaf.
+	 */
+
+	i915_syncmap_init(&sync);
+	do {
+		u64 context = i915_prandom_u64_state(&prng) & ~MASK;
+		unsigned int idx;
+
+		if (i915_syncmap_is_later(&sync, context, 0)) /* Skip repeats */
+			continue;
+
+		for (idx = 0; idx < KSYNCMAP; idx++) {
+			err = i915_syncmap_set(&sync, context + idx, 0);
+			if (err)
+				goto out;
+
+			if (sync->height) {
+				pr_err("Inserting context=%llx did not return leaf (height=%d, prefix=%llx\n",
+				       context, sync->height, sync->prefix);
+				err = -EINVAL;
+				goto out;
+			}
+
+			if (sync->bitmap != BIT(idx + 1) - 1) {
+				pr_err("Inserting neighbouring context=0x%llx+%d, did not fit into the same leaf bitmap=%x (%d), expected %lx (%d)\n",
+				       context, idx,
+				       sync->bitmap, hweight32(sync->bitmap),
+				       BIT(idx + 1) - 1, idx + 1);
+				err = -EINVAL;
+				goto out;
+			}
+		}
+	} while (!__igt_timeout(end_time, NULL));
+out:
+	return dump_syncmap(sync, err);
+}
+
+static int igt_syncmap_compact(void *arg)
+{
+	struct i915_syncmap *sync;
+	unsigned int idx, order;
+	int err;
+
+	i915_syncmap_init(&sync);
+
+	/*
+	 * The syncmap are "space efficient" compressed radix trees - any
+	 * branch with only one child is skipped and replaced by the child.
+	 *
+	 * If we construct a tree with ids that are neighbouring at a non-zero
+	 * height, we form a join but each child of that join is directly a
+	 * leaf holding the single id.
+	 */
+	for (order = SHIFT; order < 64; order += SHIFT) {
+		err = check_syncmap_free(&sync);
+		if (err)
+			goto out;
+
+		/* Create neighbours in the parent */
+		for (idx = 0; idx < KSYNCMAP; idx++) {
+			u64 context = idx * BIT_ULL(order) + idx;
+
+			err = i915_syncmap_set(&sync, context, 0);
+			if (err)
+				goto out;
+
+			if (sync->height) {
+				pr_err("Inserting context=%llx (order=%d, idx=%d) did not return leaf (height=%d, prefix=%llx\n",
+				       context, order, idx,
+				       sync->height, sync->prefix);
+				err = -EINVAL;
+				goto out;
+			}
+		}
+
+		sync = sync->parent;
+		if (sync->parent) {
+			pr_err("Parent (join) of last leaf was not the sync!\n");
+			err = -EINVAL;
+			goto out;
+		}
+
+		if (sync->height != order) {
+			pr_err("Join does not have the expected height, found %d, expected %d\n",
+			       sync->height, order);
+			err = -EINVAL;
+			goto out;
+		}
+
+		if (sync->bitmap != BIT(KSYNCMAP) - 1) {
+			pr_err("Join is not full!, found %x (%d) expected %lx (%d)\n",
+			       sync->bitmap, hweight32(sync->bitmap),
+			       BIT(KSYNCMAP) - 1, KSYNCMAP);
+			err = -EINVAL;
+			goto out;
+		}
+
+		/* Each of our children should be a leaf */
+		for (idx = 0; idx < KSYNCMAP; idx++) {
+			struct i915_syncmap *leaf = __sync_child(sync)[idx];
+
+			if (leaf->height) {
+				pr_err("Child %d is a not leaf!\n", idx);
+				err = -EINVAL;
+				goto out;
+			}
+
+			if (leaf->parent != sync) {
+				pr_err("Child %d is not attached to us!\n",
+				       idx);
+				err = -EINVAL;
+				goto out;
+			}
+
+			if (!is_power_of_2(leaf->bitmap)) {
+				pr_err("Child %d holds more than one id, found %x (%d)\n",
+				       idx, leaf->bitmap, hweight32(leaf->bitmap));
+				err = -EINVAL;
+				goto out;
+			}
+
+			if (leaf->bitmap != BIT(idx)) {
+				pr_err("Child %d has wrong seqno idx, found %d, expected %d\n",
+				       idx, ilog2(leaf->bitmap), idx);
+				err = -EINVAL;
+				goto out;
+			}
+		}
+	}
+out:
+	return dump_syncmap(sync, err);
+}
+
+static int igt_syncmap_random(void *arg)
+{
+	I915_RND_STATE(prng);
+	IGT_TIMEOUT(end_time);
+	struct i915_syncmap *sync;
+	unsigned long count, phase, i;
+	u32 seqno;
+	int err;
+
+	i915_syncmap_init(&sync);
+
+	/*
+	 * Having tried to test the individual operations within i915_syncmap,
+	 * run a smoketest exploring the entire u64 space with random
+	 * insertions.
+	 */
+
+	count = 0;
+	phase = jiffies + HZ/100 + 1;
+	do {
+		u64 context = i915_prandom_u64_state(&prng);
+
+		err = i915_syncmap_set(&sync, context, 0);
+		if (err)
+			goto out;
+
+		count++;
+	} while (!time_after(jiffies, phase));
+	seqno = 0;
+
+	phase = 0;
+	do {
+		I915_RND_STATE(ctx);
+		u32 last_seqno = seqno;
+		bool expect;
+
+		seqno = prandom_u32_state(&prng);
+		expect = seqno_later(last_seqno, seqno);
+
+		for (i = 0; i < count; i++) {
+			u64 context = i915_prandom_u64_state(&ctx);
+
+			if (i915_syncmap_is_later(&sync, context, seqno) != expect) {
+				pr_err("context=%llu, last=%u this=%u did not match expectation (%d)\n",
+				       context, last_seqno, seqno, expect);
+				err = -EINVAL;
+				goto out;
+			}
+
+			err = i915_syncmap_set(&sync, context, seqno);
+			if (err)
+				goto out;
+		}
+
+		phase++;
+	} while (!__igt_timeout(end_time, NULL));
+	pr_debug("Completed %lu passes, each of %lu contexts\n", phase, count);
+out:
+	return dump_syncmap(sync, err);
+}
+
+int i915_syncmap_mock_selftests(void)
+{
+	static const struct i915_subtest tests[] = {
+		SUBTEST(igt_syncmap_init),
+		SUBTEST(igt_syncmap_one),
+		SUBTEST(igt_syncmap_join_above),
+		SUBTEST(igt_syncmap_join_below),
+		SUBTEST(igt_syncmap_neighbours),
+		SUBTEST(igt_syncmap_compact),
+		SUBTEST(igt_syncmap_random),
+	};
+
+	return i915_subtests(tests, NULL);
+}
diff --git a/drivers/gpu/drm/i915/selftests/mock_timeline.c b/drivers/gpu/drm/i915/selftests/mock_timeline.c
new file mode 100644
index 0000000..47b1f47
--- /dev/null
+++ b/drivers/gpu/drm/i915/selftests/mock_timeline.c
@@ -0,0 +1,45 @@
+/*
+ * Copyright © 2017 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.
+ *
+ */
+
+#include "mock_timeline.h"
+
+struct intel_timeline *mock_timeline(u64 context)
+{
+	static struct lock_class_key class;
+	struct intel_timeline *tl;
+
+	tl = kzalloc(sizeof(*tl), GFP_KERNEL);
+	if (!tl)
+		return NULL;
+
+	__intel_timeline_init(tl, NULL, context, &class, "mock");
+
+	return tl;
+}
+
+void mock_timeline_destroy(struct intel_timeline *tl)
+{
+	__intel_timeline_fini(tl);
+	kfree(tl);
+}
diff --git a/drivers/gpu/drm/i915/selftests/mock_timeline.h b/drivers/gpu/drm/i915/selftests/mock_timeline.h
new file mode 100644
index 0000000..c27ff46
--- /dev/null
+++ b/drivers/gpu/drm/i915/selftests/mock_timeline.h
@@ -0,0 +1,33 @@
+/*
+ * Copyright © 2017 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 __MOCK_TIMELINE__
+#define __MOCK_TIMELINE__
+
+#include "../i915_gem_timeline.h"
+
+struct intel_timeline *mock_timeline(u64 context);
+void mock_timeline_destroy(struct intel_timeline *tl);
+
+#endif /* !__MOCK_TIMELINE__ */