On 11/01/2021 10:57, Chris Wilson wrote:
On the off chance that we need to arbitrate before launching the
payload, perform the check after we signal the request is ready to
start. Assuming instantaneous processing of the CS event, the request
will then be treated as having started when we make the decisions as to
how to process that CS event.
What is the wider context with this change?
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/gt/gen8_engine_cs.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/gen8_engine_cs.c b/drivers/gpu/drm/i915/gt/gen8_engine_cs.c
index 2e36e0a9d8a6..9a182652a35e 100644
--- a/drivers/gpu/drm/i915/gt/gen8_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/gen8_engine_cs.c
@@ -361,19 +361,19 @@ int gen8_emit_init_breadcrumb(struct i915_request *rq)
if (IS_ERR(cs))
return PTR_ERR(cs);
+ *cs++ = MI_STORE_DWORD_IMM_GEN4 | MI_USE_GGTT;
+ *cs++ = hwsp_offset(rq);
+ *cs++ = 0;
+ *cs++ = rq->fence.seqno - 1;
+
Strictly this movement even makes the existing comment (below) more correct.
/*
* Check if we have been preempted before we even get started.
*
* After this point i915_request_started() reports true, even if
* we get preempted and so are no longer running.
*/
- *cs++ = MI_ARB_CHECK;
*cs++ = MI_NOOP;
-
- *cs++ = MI_STORE_DWORD_IMM_GEN4 | MI_USE_GGTT;
- *cs++ = hwsp_offset(rq);
- *cs++ = 0;
- *cs++ = rq->fence.seqno - 1;
+ *cs++ = MI_ARB_CHECK;
Special reason to have NOOP before MI_ARB_CHECK or would more common
NOOP padding at the end be suitable?
Regards,
Tvrtko
intel_ring_advance(rq, cs);
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