[Intel-gfx] [PATCH 33/33] 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.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
---
 drivers/gpu/drm/i915/gt/intel_lrc.c | 40 ++++++++++++++++++-----------
 1 file changed, 25 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index 8765b7d91833..e93ea7e25b08 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -5407,6 +5407,14 @@ static struct intel_timeline *pinned_timeline(struct intel_context *ce)
 						 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_CONTEXT);
+}
+
 static int __execlists_context_alloc(struct intel_context *ce,
 				     struct intel_engine_cs *engine)
 {
@@ -5437,6 +5445,19 @@ static int __execlists_context_alloc(struct intel_context *ce,
 		goto error_deref_obj;
 	}
 
+	ring = intel_engine_create_ring(engine, (unsigned long)ce->ring);
+	if (IS_ERR(ring)) {
+		ret = PTR_ERR(ring);
+		goto error_deref_obj;
+	}
+
+	ret = populate_lr_context(ce, ctx_obj, engine, ring);
+	if (ret) {
+		drm_dbg(&engine->i915->drm,
+			"Failed to populate LRC: %d\n", ret);
+		goto error_ring_free;
+	}
+
 	if (!page_mask_bits(ce->timeline)) {
 		struct intel_timeline *tl;
 
@@ -5446,29 +5467,18 @@ static int __execlists_context_alloc(struct intel_context *ce,
 		 */
 		if (unlikely(ce->timeline))
 			tl = pinned_timeline(ce);
-		else
+		else if (intel_engine_has_semaphores(engine))
 			tl = intel_timeline_create(engine->gt);
+		else
+			tl = pphwsp_timeline(ce, vma);
 		if (IS_ERR(tl)) {
 			ret = PTR_ERR(tl);
-			goto error_deref_obj;
+			goto error_ring_free;
 		}
 
 		ce->timeline = tl;
 	}
 
-	ring = intel_engine_create_ring(engine, (unsigned long)ce->ring);
-	if (IS_ERR(ring)) {
-		ret = PTR_ERR(ring);
-		goto error_deref_obj;
-	}
-
-	ret = populate_lr_context(ce, ctx_obj, engine, ring);
-	if (ret) {
-		drm_dbg(&engine->i915->drm,
-			"Failed to populate LRC: %d\n", ret);
-		goto error_ring_free;
-	}
-
 	ce->ring = ring;
 	ce->state = vma;
 
-- 
2.20.1