[PATCH 45/53] drm/i915/gt: Use ppHWSP for unshared non-semaphore related timelines

[Chris Wilson]

When we are not using semaphores with a context/engine, we can simply
reuse the same seqno location across wraps, but we still require each
timeline to have its own address. For LRC submission, each context is
prefixed by a per-process HWSP, which provides us with a unique location
for each context-local timeline. A shared timeline that is common to
multiple contexts will continue to use a separate page.

This enables us to create position invariant contexts should we feel the
need to relocate them.

Initially they are automatically used by Broadwell/Braswell as they do
not require independent timelines.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost at intel.com>
---
 drivers/gpu/drm/i915/gt/intel_lrc.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index 4e856947fb13..240581247de6 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -834,6 +834,14 @@ pinned_timeline(struct intel_context *ce, struct intel_engine_cs *engine)
 	return intel_timeline_create_from_engine(engine, page_unmask_bits(tl));
 }
 
+static struct intel_timeline *
+pphwsp_timeline(struct intel_context *ce, struct i915_vma *state)
+{
+	return __intel_timeline_create(ce->engine->gt, state,
+				       I915_GEM_HWS_SEQNO_ADDR |
+				       INTEL_TIMELINE_RELATIVE_CONTEXT);
+}
+
 int lrc_alloc(struct intel_context *ce, struct intel_engine_cs *engine)
 {
 	struct intel_ring *ring;
@@ -861,8 +869,10 @@ int lrc_alloc(struct intel_context *ce, struct intel_engine_cs *engine)
 		 */
 		if (unlikely(ce->timeline))
 			tl = pinned_timeline(ce, engine);
-		else
+		else if (intel_engine_has_semaphores(engine))
 			tl = intel_timeline_create(engine->gt);
+		else
+			tl = pphwsp_timeline(ce, vma);
 		if (IS_ERR(tl)) {
 			err = PTR_ERR(tl);
 			goto err_ring;
-- 
2.20.1