Ensure H2G buffer updates are visible before descriptor tail updates by
inserting a barrier between the H2G buffer update and the tail. The
barrier is simple wmb() for SMEM and is register write for LMEM. This is
needed if more than 1 H2G can be inflight at once.
Signed-off-by: Matthew Brost <matthew.brost@xxxxxxxxx>
Cc: Michal Wajdeczko <michal.wajdeczko@xxxxxxxxx>
---
drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
index fb875d257536..42063e1c355d 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_ct.c
@@ -328,6 +328,18 @@ static u32 ct_get_next_fence(struct intel_guc_ct *ct)
return ++ct->requests.last_fence;
}
+static void write_barrier(struct intel_guc_ct *ct) {
+ struct intel_guc *guc = ct_to_guc(ct);
+ struct intel_gt *gt = guc_to_gt(guc);
+
+ if (i915_gem_object_is_lmem(guc->ct.vma->obj)) {
+ GEM_BUG_ON(guc->send_regs.fw_domains);
+ intel_uncore_write_fw(gt->uncore, GEN11_SOFT_SCRATCH(0), 0);
+ } else {
+ wmb();
+ }
+}
+
/**
* DOC: CTB Host to GuC request
*
@@ -411,6 +423,12 @@ static int ct_write(struct intel_guc_ct *ct,
}
GEM_BUG_ON(tail > size);
+ /*
+ * make sure H2G buffer update and LRC tail update (if this triggering a
+ * submission) are visible before updating the descriptor tail
+ */
+ write_barrier(ct);
+
/* now update desc tail (back in bytes) */
desc->tail = tail * 4;
return 0;
--
2.28.0
