Rather than using wait_for_atomic() when chacking for a response from
the GuC, we can get the effect of a hybrid spin/sleep wait by breaking
it into two stages. First, spin-wait for up to 10us to minimise latency
for "quick" commands; then, if that times out, sleep-wait for up 10ms
(the maximum allowed for a "slow" command).
Being able to do this depends on the recent patch
18f4b84 drm/i915: Use atomic waits for short non-atomic ones
and is similar to the hybrid approach in
1758b90 drm/i915: Use a hybrid scheme for fast register waits
(although we can't use that as-is, because that interface doesn't quite
match what we need here).
Signed-off-by: Dave Gordon <david.s.gordon@xxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_guc_submission.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
index bfc8bf6..2112e02 100644
--- a/drivers/gpu/drm/i915/i915_guc_submission.c
+++ b/drivers/gpu/drm/i915/i915_guc_submission.c
@@ -97,8 +97,14 @@ static int host2guc_action(struct intel_guc *guc, u32 *data, u32 len)
I915_WRITE(HOST2GUC_INTERRUPT, HOST2GUC_TRIGGER);
- /* No HOST2GUC command should take longer than 10ms */
- ret = wait_for_atomic(host2guc_action_response(dev_priv, &status), 10);
+ /*
+ * Fast commands should complete in less than 10us, so sample quickly
+ * up to that length of time, then switch to a slower sleep-wait loop.
+ * No HOST2GUC command should ever take longer than 10ms.
+ */
+ ret = wait_for_us(host2guc_action_response(dev_priv, &status), 10);
+ if (ret)
+ ret = wait_for(host2guc_action_response(dev_priv, &status), 10);
if (status != GUC2HOST_STATUS_SUCCESS) {
/*
* Either the GuC explicitly returned an error (which
--
1.9.1
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