[igt-dev] [PATCH i-g-t v2 02/18] lib/intel_batchbuffer: Add control over fencing in intel_bb

[Dominik Grzegorzek]

From: Zbigniew Kempczyński <zbigniew.kempczynski at intel.com>

>From default intel_bb uses fencing to track subsequent execs.
It is required to properly sync intel_bb. Unfortunately this
also has some drawback, when we want to use same intel_bb to
schedule some time consuming job then run something else. Fencing
as turned on from default will serialize such execs. To avoid that
add possibility to turn on / off fencing in the intel_bb.

Signed-off-by: Zbigniew Kempczyński <zbigniew.kempczynski at intel.com>
Cc: Dominik Grzegorzek <dominik.grzegorzek at intel.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
---
 lib/intel_batchbuffer.c | 47 ++++++++++++++++++++++++++++++++---------
 lib/intel_batchbuffer.h |  2 ++
 2 files changed, 39 insertions(+), 10 deletions(-)

diff --git a/lib/intel_batchbuffer.c b/lib/intel_batchbuffer.c
index be764646..079d6389 100644
--- a/lib/intel_batchbuffer.c
+++ b/lib/intel_batchbuffer.c
@@ -1266,6 +1266,7 @@ __intel_bb_create(int i915, uint32_t size, bool do_relocs)
 	ibb->ptr = ibb->batch;
 	ibb->prng = (uint32_t) to_user_pointer(ibb);
 	ibb->fence = -1;
+	ibb->use_fences = true;
 
 	gtt_size = gem_aperture_size(i915);
 	if (!gem_uses_full_ppgtt(i915))
@@ -1513,6 +1514,26 @@ void intel_bb_set_debug(struct intel_bb *ibb, bool debug)
 	ibb->debug = debug;
 }
 
+/**
+ * intel_bb_set_fencing:
+ * @ibb: pointer to intel_bb
+ * @use_fences: true / false
+ *
+ * Sets using fences to true / false.
+ */
+void intel_bb_set_fencing(struct intel_bb *ibb, bool use_fences)
+{
+	if (use_fences == ibb->use_fences)
+		return;
+
+	if (use_fences == false && ibb->fence >= 0) {
+		close(ibb->fence);
+		ibb->fence = -1;
+	}
+
+	ibb->use_fences = use_fences;
+}
+
 /**
  * intel_bb_set_dump_base64:
  * @ibb: pointer to intel_bb
@@ -2058,7 +2079,11 @@ int __intel_bb_exec(struct intel_bb *ibb, uint32_t end_offset,
 	execbuf.buffer_count = ibb->num_objects;
 	execbuf.batch_len = end_offset;
 	execbuf.rsvd1 = ibb->ctx = ctx;
-	execbuf.flags = flags | I915_EXEC_BATCH_FIRST | I915_EXEC_FENCE_OUT;
+	execbuf.flags = flags | I915_EXEC_BATCH_FIRST;
+
+	if (ibb->use_fences)
+		execbuf.flags |= I915_EXEC_FENCE_OUT;
+
 	if (ibb->enforce_relocs)
 		execbuf.flags &= ~I915_EXEC_NO_RELOC;
 	execbuf.rsvd2 = 0;
@@ -2077,15 +2102,17 @@ int __intel_bb_exec(struct intel_bb *ibb, uint32_t end_offset,
 	update_offsets(ibb, objects);
 
 	/* Save/merge fences */
-	fence = execbuf.rsvd2 >> 32;
-
-	if (ibb->fence < 0) {
-		ibb->fence = fence;
-	} else {
-		new_fence = sync_fence_merge(ibb->fence, fence);
-		close(ibb->fence);
-		close(fence);
-		ibb->fence = new_fence;
+	if (ibb->use_fences) {
+		fence = execbuf.rsvd2 >> 32;
+
+		if (ibb->fence < 0) {
+			ibb->fence = fence;
+		} else {
+			new_fence = sync_fence_merge(ibb->fence, fence);
+			close(ibb->fence);
+			close(fence);
+			ibb->fence = new_fence;
+		}
 	}
 
 	if (sync || ibb->debug)
diff --git a/lib/intel_batchbuffer.h b/lib/intel_batchbuffer.h
index 8b9c1ed9..cbfbe25f 100644
--- a/lib/intel_batchbuffer.h
+++ b/lib/intel_batchbuffer.h
@@ -446,6 +446,7 @@ struct intel_bb {
 	uint32_t *ptr;
 	uint64_t alignment;
 	int fence;
+	bool use_fences;
 
 	uint32_t prng;
 	uint64_t gtt_size;
@@ -497,6 +498,7 @@ int intel_bb_sync(struct intel_bb *ibb);
 void intel_bb_print(struct intel_bb *ibb);
 void intel_bb_dump(struct intel_bb *ibb, const char *filename);
 void intel_bb_set_debug(struct intel_bb *ibb, bool debug);
+void intel_bb_set_fencing(struct intel_bb *ibb, bool use_fences);
 void intel_bb_set_dump_base64(struct intel_bb *ibb, bool dump);
 
 static inline uint64_t
-- 
2.20.1