drm/i915: Allocate a status page for each timeline

Allocate a page for use as a status page by a group of timelines, as we
only need a dword of storage for each (rounded up to the cacheline for
safety) we can pack multiple timelines into the same page. Each timeline
will then be able to track its own HW seqno.

v2: Reuse the common per-engine HWSP for the solitary ringbuffer
timeline, so that we do not have to emit (using per-gen specialised
vfuncs) the breadcrumb into the distinct timeline HWSP and instead can
keep on using the common MI_STORE_DWORD_INDEX. However, to maintain the
sleight-of-hand for the global/per-context seqno switchover, we will
store both temporarily (and so use a custom offset for the shared timeline
HWSP until the switch over).

v3: Keep things simple and allocate a page for each timeline, page
sharing comes next.

v4: I was caught repeating the same MI_STORE_DWORD_IMM over and over
again in selftests.

v5: And caught red handed copying create timeline + check.

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/20190128181812.22804-3-chris@chris-wilson.co.uk

10 files changed, 543 insertions, 56 deletions

diff --git a/drivers/gpu/drm/i915/i915_timeline.c b/drivers/gpu/drm/i915/i915_timeline.c
index 84550f17d3df..8d5792311a8f 100644
--- a/drivers/gpu/drm/i915/i915_timeline.c
+++ b/drivers/gpu/drm/i915/i915_timeline.c
@@ -9,28 +9,78 @@
 #include "i915_timeline.h"
 #include "i915_syncmap.h"
 
-void i915_timeline_init(struct drm_i915_private *i915,
-			struct i915_timeline *timeline,
-			const char *name)
+static struct i915_vma *__hwsp_alloc(struct drm_i915_private *i915)
+{
+	struct drm_i915_gem_object *obj;
+	struct i915_vma *vma;
+
+	obj = i915_gem_object_create_internal(i915, PAGE_SIZE);
+	if (IS_ERR(obj))
+		return ERR_CAST(obj);
+
+	i915_gem_object_set_cache_coherency(obj, I915_CACHE_LLC);
+
+	vma = i915_vma_instance(obj, &i915->ggtt.vm, NULL);
+	if (IS_ERR(vma))
+		i915_gem_object_put(obj);
+
+	return vma;
+}
+
+static int hwsp_alloc(struct i915_timeline *timeline)
+{
+	struct i915_vma *vma;
+
+	vma = __hwsp_alloc(timeline->i915);
+	if (IS_ERR(vma))
+		return PTR_ERR(vma);
+
+	timeline->hwsp_ggtt = vma;
+	timeline->hwsp_offset = 0;
+
+	return 0;
+}
+
+int i915_timeline_init(struct drm_i915_private *i915,
+		       struct i915_timeline *timeline,
+		       const char *name,
+		       struct i915_vma *global_hwsp)
 {
 	struct i915_gt_timelines *gt = &i915->gt.timelines;
+	void *vaddr;
+	int err;
 
 	/*
 	 * 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.
+	 *
+	 * Called during early_init before we know how many engines there are.
 	 */
 	BUILD_BUG_ON(KSYNCMAP < I915_NUM_ENGINES);
 
 	timeline->i915 = i915;
 	timeline->name = name;
+	timeline->pin_count = 0;
+
+	if (global_hwsp) {
+		timeline->hwsp_ggtt = i915_vma_get(global_hwsp);
+		timeline->hwsp_offset = I915_GEM_HWS_SEQNO_ADDR;
+	} else {
+		err = hwsp_alloc(timeline);
+		if (err)
+			return err;
+	}
 
-	mutex_lock(&gt->mutex);
-	list_add(&timeline->link, &gt->list);
-	mutex_unlock(&gt->mutex);
+	vaddr = i915_gem_object_pin_map(timeline->hwsp_ggtt->obj, I915_MAP_WB);
+	if (IS_ERR(vaddr)) {
+		i915_vma_put(timeline->hwsp_ggtt);
+		return PTR_ERR(vaddr);
+	}
 
-	/* Called during early_init before we know how many engines there are */
+	timeline->hwsp_seqno =
+		memset(vaddr + timeline->hwsp_offset, 0, CACHELINE_BYTES);
 
 	timeline->fence_context = dma_fence_context_alloc(1);
 
@@ -40,6 +90,12 @@ void i915_timeline_init(struct drm_i915_private *i915,
 	INIT_LIST_HEAD(&timeline->requests);
 
 	i915_syncmap_init(&timeline->sync);
+
+	mutex_lock(&gt->mutex);
+	list_add(&timeline->link, &gt->list);
+	mutex_unlock(&gt->mutex);
+
+	return 0;
 }
 
 void i915_timelines_init(struct drm_i915_private *i915)
@@ -85,6 +141,7 @@ void i915_timeline_fini(struct i915_timeline *timeline)
 {
 	struct i915_gt_timelines *gt = &timeline->i915->gt.timelines;
 
+	GEM_BUG_ON(timeline->pin_count);
 	GEM_BUG_ON(!list_empty(&timeline->requests));
 
 	i915_syncmap_free(&timeline->sync);
@@ -92,23 +149,69 @@ void i915_timeline_fini(struct i915_timeline *timeline)
 	mutex_lock(&gt->mutex);
 	list_del(&timeline->link);
 	mutex_unlock(&gt->mutex);
+
+	i915_gem_object_unpin_map(timeline->hwsp_ggtt->obj);
+	i915_vma_put(timeline->hwsp_ggtt);
 }
 
 struct i915_timeline *
-i915_timeline_create(struct drm_i915_private *i915, const char *name)
+i915_timeline_create(struct drm_i915_private *i915,
+		     const char *name,
+		     struct i915_vma *global_hwsp)
 {
 	struct i915_timeline *timeline;
+	int err;
 
 	timeline = kzalloc(sizeof(*timeline), GFP_KERNEL);
 	if (!timeline)
 		return ERR_PTR(-ENOMEM);
 
-	i915_timeline_init(i915, timeline, name);
+	err = i915_timeline_init(i915, timeline, name, global_hwsp);
+	if (err) {
+		kfree(timeline);
+		return ERR_PTR(err);
+	}
+
 	kref_init(&timeline->kref);
 
 	return timeline;
 }
 
+int i915_timeline_pin(struct i915_timeline *tl)
+{
+	int err;
+
+	if (tl->pin_count++)
+		return 0;
+	GEM_BUG_ON(!tl->pin_count);
+
+	err = i915_vma_pin(tl->hwsp_ggtt, 0, 0, PIN_GLOBAL | PIN_HIGH);
+	if (err)
+		goto unpin;
+
+	return 0;
+
+unpin:
+	tl->pin_count = 0;
+	return err;
+}
+
+void i915_timeline_unpin(struct i915_timeline *tl)
+{
+	GEM_BUG_ON(!tl->pin_count);
+	if (--tl->pin_count)
+		return;
+
+	/*
+	 * Since this timeline is idle, all bariers upon which we were waiting
+	 * must also be complete and so we can discard the last used barriers
+	 * without loss of information.
+	 */
+	i915_syncmap_free(&tl->sync);
+
+	__i915_vma_unpin(tl->hwsp_ggtt);
+}
+
 void __i915_timeline_free(struct kref *kref)
 {
 	struct i915_timeline *timeline =
diff --git a/drivers/gpu/drm/i915/i915_timeline.h b/drivers/gpu/drm/i915/i915_timeline.h
index 87ad2dd31c20..0c3739d53d79 100644
--- a/drivers/gpu/drm/i915/i915_timeline.h
+++ b/drivers/gpu/drm/i915/i915_timeline.h
@@ -32,6 +32,8 @@
 #include "i915_syncmap.h"
 #include "i915_utils.h"
 
+struct i915_vma;
+
 struct i915_timeline {
 	u64 fence_context;
 	u32 seqno;
@@ -40,6 +42,11 @@ struct i915_timeline {
 #define TIMELINE_CLIENT 0 /* default subclass */
 #define TIMELINE_ENGINE 1
 
+	unsigned int pin_count;
+	const u32 *hwsp_seqno;
+	struct i915_vma *hwsp_ggtt;
+	u32 hwsp_offset;
+
 	/**
 	 * List of breadcrumbs associated with GPU requests currently
 	 * outstanding.
@@ -71,9 +78,10 @@ struct i915_timeline {
 	struct kref kref;
 };
 
-void i915_timeline_init(struct drm_i915_private *i915,
-			struct i915_timeline *tl,
-			const char *name);
+int i915_timeline_init(struct drm_i915_private *i915,
+		       struct i915_timeline *tl,
+		       const char *name,
+		       struct i915_vma *hwsp);
 void i915_timeline_fini(struct i915_timeline *tl);
 
 static inline void
@@ -96,7 +104,9 @@ i915_timeline_set_subclass(struct i915_timeline *timeline,
 }
 
 struct i915_timeline *
-i915_timeline_create(struct drm_i915_private *i915, const char *name);
+i915_timeline_create(struct drm_i915_private *i915,
+		     const char *name,
+		     struct i915_vma *global_hwsp);
 
 static inline struct i915_timeline *
 i915_timeline_get(struct i915_timeline *timeline)
@@ -135,6 +145,9 @@ static inline bool i915_timeline_sync_is_later(struct i915_timeline *tl,
 	return __i915_timeline_sync_is_later(tl, fence->context, fence->seqno);
 }
 
+int i915_timeline_pin(struct i915_timeline *tl);
+void i915_timeline_unpin(struct i915_timeline *tl);
+
 void i915_timelines_init(struct drm_i915_private *i915);
 void i915_timelines_park(struct drm_i915_private *i915);
 void i915_timelines_fini(struct drm_i915_private *i915);
diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index 2657eb6fd914..515e87846afd 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -484,26 +484,6 @@ static void intel_engine_init_execlist(struct intel_engine_cs *engine)
 	execlists->queue = RB_ROOT_CACHED;
 }
 
-/**
- * intel_engines_setup_common - setup engine state not requiring hw access
- * @engine: Engine to setup.
- *
- * Initializes @engine@ structure members shared between legacy and execlists
- * submission modes which do not require hardware access.
- *
- * Typically done early in the submission mode specific engine setup stage.
- */
-void intel_engine_setup_common(struct intel_engine_cs *engine)
-{
-	i915_timeline_init(engine->i915, &engine->timeline, engine->name);
-	i915_timeline_set_subclass(&engine->timeline, TIMELINE_ENGINE);
-
-	intel_engine_init_execlist(engine);
-	intel_engine_init_hangcheck(engine);
-	intel_engine_init_batch_pool(engine);
-	intel_engine_init_cmd_parser(engine);
-}
-
 static void cleanup_status_page(struct intel_engine_cs *engine)
 {
 	struct i915_vma *vma;
@@ -601,6 +581,44 @@ err:
 	return ret;
 }
 
+/**
+ * intel_engines_setup_common - setup engine state not requiring hw access
+ * @engine: Engine to setup.
+ *
+ * Initializes @engine@ structure members shared between legacy and execlists
+ * submission modes which do not require hardware access.
+ *
+ * Typically done early in the submission mode specific engine setup stage.
+ */
+int intel_engine_setup_common(struct intel_engine_cs *engine)
+{
+	int err;
+
+	err = init_status_page(engine);
+	if (err)
+		return err;
+
+	err = i915_timeline_init(engine->i915,
+				 &engine->timeline,
+				 engine->name,
+				 engine->status_page.vma);
+	if (err)
+		goto err_hwsp;
+
+	i915_timeline_set_subclass(&engine->timeline, TIMELINE_ENGINE);
+
+	intel_engine_init_execlist(engine);
+	intel_engine_init_hangcheck(engine);
+	intel_engine_init_batch_pool(engine);
+	intel_engine_init_cmd_parser(engine);
+
+	return 0;
+
+err_hwsp:
+	cleanup_status_page(engine);
+	return err;
+}
+
 static void __intel_context_unpin(struct i915_gem_context *ctx,
 				  struct intel_engine_cs *engine)
 {
@@ -617,7 +635,7 @@ struct measure_breadcrumb {
 static int measure_breadcrumb_dw(struct intel_engine_cs *engine)
 {
 	struct measure_breadcrumb *frame;
-	unsigned int dw;
+	int dw = -ENOMEM;
 
 	GEM_BUG_ON(!engine->i915->gt.scratch);
 
@@ -625,7 +643,10 @@ static int measure_breadcrumb_dw(struct intel_engine_cs *engine)
 	if (!frame)
 		return -ENOMEM;
 
-	i915_timeline_init(engine->i915, &frame->timeline, "measure");
+	if (i915_timeline_init(engine->i915,
+			       &frame->timeline, "measure",
+			       engine->status_page.vma))
+		goto out_frame;
 
 	INIT_LIST_HEAD(&frame->ring.request_list);
 	frame->ring.timeline = &frame->timeline;
@@ -642,8 +663,9 @@ static int measure_breadcrumb_dw(struct intel_engine_cs *engine)
 	dw = engine->emit_breadcrumb(&frame->rq, frame->cs) - frame->cs;
 
 	i915_timeline_fini(&frame->timeline);
-	kfree(frame);
 
+out_frame:
+	kfree(frame);
 	return dw;
 }
 
@@ -693,20 +715,14 @@ int intel_engine_init_common(struct intel_engine_cs *engine)
 	if (ret)
 		goto err_unpin_preempt;
 
-	ret = init_status_page(engine);
-	if (ret)
-		goto err_breadcrumbs;
-
 	ret = measure_breadcrumb_dw(engine);
 	if (ret < 0)
-		goto err_status_page;
+		goto err_breadcrumbs;
 
 	engine->emit_breadcrumb_dw = ret;
 
 	return 0;
 
-err_status_page:
-	cleanup_status_page(engine);
 err_breadcrumbs:
 	intel_engine_fini_breadcrumbs(engine);
 err_unpin_preempt:
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 9ae7f77293a0..e388f37743a2 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -2206,10 +2206,14 @@ logical_ring_default_irqs(struct intel_engine_cs *engine)
 	engine->irq_keep_mask = GT_CONTEXT_SWITCH_INTERRUPT << shift;
 }
 
-static void
+static int
 logical_ring_setup(struct intel_engine_cs *engine)
 {
-	intel_engine_setup_common(engine);
+	int err;
+
+	err = intel_engine_setup_common(engine);
+	if (err)
+		return err;
 
 	/* Intentionally left blank. */
 	engine->buffer = NULL;
@@ -2219,6 +2223,8 @@ logical_ring_setup(struct intel_engine_cs *engine)
 
 	logical_ring_default_vfuncs(engine);
 	logical_ring_default_irqs(engine);
+
+	return 0;
 }
 
 static int logical_ring_init(struct intel_engine_cs *engine)
@@ -2267,7 +2273,9 @@ int logical_render_ring_init(struct intel_engine_cs *engine)
 {
 	int ret;
 
-	logical_ring_setup(engine);
+	ret = logical_ring_setup(engine);
+	if (ret)
+		return ret;
 
 	/* Override some for render ring. */
 	engine->init_context = gen8_init_rcs_context;
@@ -2296,7 +2304,11 @@ int logical_render_ring_init(struct intel_engine_cs *engine)
 
 int logical_xcs_ring_init(struct intel_engine_cs *engine)
 {
-	logical_ring_setup(engine);
+	int err;
+
+	err = logical_ring_setup(engine);
+	if (err)
+		return err;
 
 	return logical_ring_init(engine);
 }
@@ -2629,7 +2641,7 @@ static int execlists_context_deferred_alloc(struct i915_gem_context *ctx,
 		goto error_deref_obj;
 	}
 
-	timeline = i915_timeline_create(ctx->i915, ctx->name);
+	timeline = i915_timeline_create(ctx->i915, ctx->name, NULL);
 	if (IS_ERR(timeline)) {
 		ret = PTR_ERR(timeline);
 		goto error_deref_obj;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index cb6d2aa2a829..174795622eb1 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1545,9 +1545,13 @@ static int intel_init_ring_buffer(struct intel_engine_cs *engine)
 	struct intel_ring *ring;
 	int err;
 
-	intel_engine_setup_common(engine);
+	err = intel_engine_setup_common(engine);
+	if (err)
+		return err;
 
-	timeline = i915_timeline_create(engine->i915, engine->name);
+	timeline = i915_timeline_create(engine->i915,
+					engine->name,
+					engine->status_page.vma);
 	if (IS_ERR(timeline)) {
 		err = PTR_ERR(timeline);
 		goto err;
@@ -1571,6 +1575,8 @@ static int intel_init_ring_buffer(struct intel_engine_cs *engine)
 	if (err)
 		goto err_unpin;
 
+	GEM_BUG_ON(ring->timeline->hwsp_ggtt != engine->status_page.vma);
+
 	return 0;
 
 err_unpin:
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 32371ae67f24..2927b712b973 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -712,7 +712,9 @@ intel_write_status_page(struct intel_engine_cs *engine, int reg, u32 value)
 #define I915_GEM_HWS_INDEX_ADDR		(I915_GEM_HWS_INDEX * sizeof(u32))
 #define I915_GEM_HWS_PREEMPT		0x32
 #define I915_GEM_HWS_PREEMPT_ADDR	(I915_GEM_HWS_PREEMPT * sizeof(u32))
-#define I915_GEM_HWS_SCRATCH		0x40
+#define I915_GEM_HWS_SEQNO		0x40
+#define I915_GEM_HWS_SEQNO_ADDR		(I915_GEM_HWS_SEQNO * sizeof(u32))
+#define I915_GEM_HWS_SCRATCH		0x80
 #define I915_GEM_HWS_SCRATCH_ADDR	(I915_GEM_HWS_SCRATCH * sizeof(u32))
 
 #define I915_HWS_CSB_BUF0_INDEX		0x10
@@ -818,7 +820,7 @@ intel_ring_set_tail(struct intel_ring *ring, unsigned int tail)
 
 void intel_engine_write_global_seqno(struct intel_engine_cs *engine, u32 seqno);
 
-void intel_engine_setup_common(struct intel_engine_cs *engine);
+int intel_engine_setup_common(struct intel_engine_cs *engine);
 int intel_engine_init_common(struct intel_engine_cs *engine);
 void intel_engine_cleanup_common(struct intel_engine_cs *engine);
 
diff --git a/drivers/gpu/drm/i915/selftests/i915_live_selftests.h b/drivers/gpu/drm/i915/selftests/i915_live_selftests.h
index a15713cae3b3..76b4f87fc853 100644
--- a/drivers/gpu/drm/i915/selftests/i915_live_selftests.h
+++ b/drivers/gpu/drm/i915/selftests/i915_live_selftests.h
@@ -13,6 +13,7 @@ selftest(sanitycheck, i915_live_sanitycheck) /* keep first (igt selfcheck) */
 selftest(uncore, intel_uncore_live_selftests)
 selftest(workarounds, intel_workarounds_live_selftests)
 selftest(requests, i915_request_live_selftests)
+selftest(timelines, i915_timeline_live_selftests)
 selftest(objects, i915_gem_object_live_selftests)
 selftest(dmabuf, i915_gem_dmabuf_live_selftests)
 selftest(coherency, i915_gem_coherency_live_selftests)
diff --git a/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h b/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
index 1b70208eeea7..4a83a1c6c406 100644
--- a/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
+++ b/drivers/gpu/drm/i915/selftests/i915_mock_selftests.h
@@ -16,7 +16,7 @@ selftest(syncmap, i915_syncmap_mock_selftests)
 selftest(uncore, intel_uncore_mock_selftests)
 selftest(engine, intel_engine_cs_mock_selftests)
 selftest(breadcrumbs, intel_breadcrumbs_mock_selftests)
-selftest(timelines, i915_gem_timeline_mock_selftests)
+selftest(timelines, i915_timeline_mock_selftests)
 selftest(requests, i915_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_timeline.c b/drivers/gpu/drm/i915/selftests/i915_timeline.c
index 19f1c6a5c8fb..1585b614510d 100644
--- a/drivers/gpu/drm/i915/selftests/i915_timeline.c
+++ b/drivers/gpu/drm/i915/selftests/i915_timeline.c
@@ -7,6 +7,7 @@
 #include "../i915_selftest.h"
 #include "i915_random.h"
 
+#include "igt_flush_test.h"
 #include "mock_gem_device.h"
 #include "mock_timeline.h"
 
@@ -256,7 +257,7 @@ static int bench_sync(void *arg)
 	return 0;
 }
 
-int i915_gem_timeline_mock_selftests(void)
+int i915_timeline_mock_selftests(void)
 {
 	static const struct i915_subtest tests[] = {
 		SUBTEST(igt_sync),
@@ -265,3 +266,326 @@ int i915_gem_timeline_mock_selftests(void)
 
 	return i915_subtests(tests, NULL);
 }
+
+static int emit_ggtt_store_dw(struct i915_request *rq, u32 addr, u32 value)
+{
+	u32 *cs;
+
+	cs = intel_ring_begin(rq, 4);
+	if (IS_ERR(cs))
+		return PTR_ERR(cs);
+
+	if (INTEL_GEN(rq->i915) >= 8) {
+		*cs++ = MI_STORE_DWORD_IMM_GEN4 | MI_USE_GGTT;
+		*cs++ = addr;
+		*cs++ = 0;
+		*cs++ = value;
+	} else if (INTEL_GEN(rq->i915) >= 4) {
+		*cs++ = MI_STORE_DWORD_IMM_GEN4 | MI_USE_GGTT;
+		*cs++ = 0;
+		*cs++ = addr;
+		*cs++ = value;
+	} else {
+		*cs++ = MI_STORE_DWORD_IMM | MI_MEM_VIRTUAL;
+		*cs++ = addr;
+		*cs++ = value;
+		*cs++ = MI_NOOP;
+	}
+
+	intel_ring_advance(rq, cs);
+
+	return 0;
+}
+
+static u32 hwsp_address(const struct i915_timeline *tl)
+{
+	return i915_ggtt_offset(tl->hwsp_ggtt) + tl->hwsp_offset;
+}
+
+static struct i915_request *
+tl_write(struct i915_timeline *tl, struct intel_engine_cs *engine, u32 value)
+{
+	struct i915_request *rq;
+	int err;
+
+	lockdep_assert_held(&tl->i915->drm.struct_mutex); /* lazy rq refs */
+
+	err = i915_timeline_pin(tl);
+	if (err) {
+		rq = ERR_PTR(err);
+		goto out;
+	}
+
+	rq = i915_request_alloc(engine, engine->i915->kernel_context);
+	if (IS_ERR(rq))
+		goto out_unpin;
+
+	err = emit_ggtt_store_dw(rq, hwsp_address(tl), value);
+	i915_request_add(rq);
+	if (err)
+		rq = ERR_PTR(err);
+
+out_unpin:
+	i915_timeline_unpin(tl);
+out:
+	if (IS_ERR(rq))
+		pr_err("Failed to write to timeline!\n");
+	return rq;
+}
+
+static struct i915_timeline *
+checked_i915_timeline_create(struct drm_i915_private *i915)
+{
+	struct i915_timeline *tl;
+
+	tl = i915_timeline_create(i915, "live", NULL);
+	if (IS_ERR(tl))
+		return tl;
+
+	if (*tl->hwsp_seqno != tl->seqno) {
+		pr_err("Timeline created with incorrect breadcrumb, found %x, expected %x\n",
+		       *tl->hwsp_seqno, tl->seqno);
+		i915_timeline_put(tl);
+		return ERR_PTR(-EINVAL);
+	}
+
+	return tl;
+}
+
+static int live_hwsp_engine(void *arg)
+{
+#define NUM_TIMELINES 4096
+	struct drm_i915_private *i915 = arg;
+	struct i915_timeline **timelines;
+	struct intel_engine_cs *engine;
+	enum intel_engine_id id;
+	intel_wakeref_t wakeref;
+	unsigned long count, n;
+	int err = 0;
+
+	/*
+	 * Create a bunch of timelines and check we can write
+	 * independently to each of their breadcrumb slots.
+	 */
+
+	timelines = kvmalloc_array(NUM_TIMELINES * I915_NUM_ENGINES,
+				   sizeof(*timelines),
+				   GFP_KERNEL);
+	if (!timelines)
+		return -ENOMEM;
+
+	mutex_lock(&i915->drm.struct_mutex);
+	wakeref = intel_runtime_pm_get(i915);
+
+	count = 0;
+	for_each_engine(engine, i915, id) {
+		if (!intel_engine_can_store_dword(engine))
+			continue;
+
+		for (n = 0; n < NUM_TIMELINES; n++) {
+			struct i915_timeline *tl;
+			struct i915_request *rq;
+
+			tl = checked_i915_timeline_create(i915);
+			if (IS_ERR(tl)) {
+				err = PTR_ERR(tl);
+				goto out;
+			}
+
+			rq = tl_write(tl, engine, count);
+			if (IS_ERR(rq)) {
+				i915_timeline_put(tl);
+				err = PTR_ERR(rq);
+				goto out;
+			}
+
+			timelines[count++] = tl;
+		}
+	}
+
+out:
+	if (igt_flush_test(i915, I915_WAIT_LOCKED))
+		err = -EIO;
+
+	for (n = 0; n < count; n++) {
+		struct i915_timeline *tl = timelines[n];
+
+		if (!err && *tl->hwsp_seqno != n) {
+			pr_err("Invalid seqno stored in timeline %lu, found 0x%x\n",
+			       n, *tl->hwsp_seqno);
+			err = -EINVAL;
+		}
+		i915_timeline_put(tl);
+	}
+
+	intel_runtime_pm_put(i915, wakeref);
+	mutex_unlock(&i915->drm.struct_mutex);
+
+	kvfree(timelines);
+
+	return err;
+#undef NUM_TIMELINES
+}
+
+static int live_hwsp_alternate(void *arg)
+{
+#define NUM_TIMELINES 4096
+	struct drm_i915_private *i915 = arg;
+	struct i915_timeline **timelines;
+	struct intel_engine_cs *engine;
+	enum intel_engine_id id;
+	intel_wakeref_t wakeref;
+	unsigned long count, n;
+	int err = 0;
+
+	/*
+	 * Create a bunch of timelines and check we can write
+	 * independently to each of their breadcrumb slots with adjacent
+	 * engines.
+	 */
+
+	timelines = kvmalloc_array(NUM_TIMELINES * I915_NUM_ENGINES,
+				   sizeof(*timelines),
+				   GFP_KERNEL);
+	if (!timelines)
+		return -ENOMEM;
+
+	mutex_lock(&i915->drm.struct_mutex);
+	wakeref = intel_runtime_pm_get(i915);
+
+	count = 0;
+	for (n = 0; n < NUM_TIMELINES; n++) {
+		for_each_engine(engine, i915, id) {
+			struct i915_timeline *tl;
+			struct i915_request *rq;
+
+			if (!intel_engine_can_store_dword(engine))
+				continue;
+
+			tl = checked_i915_timeline_create(i915);
+			if (IS_ERR(tl)) {
+				err = PTR_ERR(tl);
+				goto out;
+			}
+
+			rq = tl_write(tl, engine, count);
+			if (IS_ERR(rq)) {
+				i915_timeline_put(tl);
+				err = PTR_ERR(rq);
+				goto out;
+			}
+
+			timelines[count++] = tl;
+		}
+	}
+
+out:
+	if (igt_flush_test(i915, I915_WAIT_LOCKED))
+		err = -EIO;
+
+	for (n = 0; n < count; n++) {
+		struct i915_timeline *tl = timelines[n];
+
+		if (!err && *tl->hwsp_seqno != n) {
+			pr_err("Invalid seqno stored in timeline %lu, found 0x%x\n",
+			       n, *tl->hwsp_seqno);
+			err = -EINVAL;
+		}
+		i915_timeline_put(tl);
+	}
+
+	intel_runtime_pm_put(i915, wakeref);
+	mutex_unlock(&i915->drm.struct_mutex);
+
+	kvfree(timelines);
+
+	return err;
+#undef NUM_TIMELINES
+}
+
+static int live_hwsp_recycle(void *arg)
+{
+	struct drm_i915_private *i915 = arg;
+	struct intel_engine_cs *engine;
+	enum intel_engine_id id;
+	intel_wakeref_t wakeref;
+	unsigned long count;
+	int err = 0;
+
+	/*
+	 * Check seqno writes into one timeline at a time. We expect to
+	 * recycle the breadcrumb slot between iterations and neither
+	 * want to confuse ourselves or the GPU.
+	 */
+
+	mutex_lock(&i915->drm.struct_mutex);
+	wakeref = intel_runtime_pm_get(i915);
+
+	count = 0;
+	for_each_engine(engine, i915, id) {
+		IGT_TIMEOUT(end_time);
+
+		if (!intel_engine_can_store_dword(engine))
+			continue;
+
+		do {
+			struct i915_timeline *tl;
+			struct i915_request *rq;
+
+			tl = checked_i915_timeline_create(i915);
+			if (IS_ERR(tl)) {
+				err = PTR_ERR(tl);
+				goto out;
+			}
+
+			rq = tl_write(tl, engine, count);
+			if (IS_ERR(rq)) {
+				i915_timeline_put(tl);
+				err = PTR_ERR(rq);
+				goto out;
+			}
+
+			if (i915_request_wait(rq,
+					      I915_WAIT_LOCKED,
+					      HZ / 5) < 0) {
+				pr_err("Wait for timeline writes timed out!\n");
+				i915_timeline_put(tl);
+				err = -EIO;
+				goto out;
+			}
+
+			if (*tl->hwsp_seqno != count) {
+				pr_err("Invalid seqno stored in timeline %lu, found 0x%x\n",
+				       count, *tl->hwsp_seqno);
+				err = -EINVAL;
+			}
+
+			i915_timeline_put(tl);
+			count++;
+
+			if (err)
+				goto out;
+
+			i915_timelines_park(i915); /* Encourage recycling! */
+		} while (!__igt_timeout(end_time, NULL));
+	}
+
+out:
+	if (igt_flush_test(i915, I915_WAIT_LOCKED))
+		err = -EIO;
+	intel_runtime_pm_put(i915, wakeref);
+	mutex_unlock(&i915->drm.struct_mutex);
+
+	return err;
+}
+
+int i915_timeline_live_selftests(struct drm_i915_private *i915)
+{
+	static const struct i915_subtest tests[] = {
+		SUBTEST(live_hwsp_recycle),
+		SUBTEST(live_hwsp_engine),
+		SUBTEST(live_hwsp_alternate),
+	};
+
+	return i915_subtests(tests, i915);
+}
diff --git a/drivers/gpu/drm/i915/selftests/mock_engine.c b/drivers/gpu/drm/i915/selftests/mock_engine.c
index 4e5b4dc6df0f..919c89fd6ee5 100644
--- a/drivers/gpu/drm/i915/selftests/mock_engine.c
+++ b/drivers/gpu/drm/i915/selftests/mock_engine.c
@@ -39,7 +39,12 @@ static struct intel_ring *mock_ring(struct intel_engine_cs *engine)
 	if (!ring)
 		return NULL;
 
-	i915_timeline_init(engine->i915, &ring->timeline, engine->name);
+	if (i915_timeline_init(engine->i915,
+			       &ring->timeline, engine->name,
+			       NULL)) {
+		kfree(ring);
+		return NULL;
+	}
 
 	ring->base.size = sz;
 	ring->base.effective_size = sz;
@@ -208,7 +213,11 @@ struct intel_engine_cs *mock_engine(struct drm_i915_private *i915,
 	engine->base.emit_breadcrumb = mock_emit_breadcrumb;
 	engine->base.submit_request = mock_submit_request;
 
-	i915_timeline_init(i915, &engine->base.timeline, engine->base.name);
+	if (i915_timeline_init(i915,
+			       &engine->base.timeline,
+			       engine->base.name,
+			       NULL))
+		goto err_free;
 	i915_timeline_set_subclass(&engine->base.timeline, TIMELINE_ENGINE);
 
 	intel_engine_init_breadcrumbs(&engine->base);
@@ -226,6 +235,7 @@ struct intel_engine_cs *mock_engine(struct drm_i915_private *i915,
 err_breadcrumbs:
 	intel_engine_fini_breadcrumbs(&engine->base);
 	i915_timeline_fini(&engine->base.timeline);
+err_free:
 	kfree(engine);
 	return NULL;
 }