From ab0e455bd0abe2b817c896b229b08045bafbdb94 Mon Sep 17 00:00:00 2001 From: Dave Gordon Date: Wed, 6 Jul 2016 15:30:11 +0100 Subject: [PATCH] drm/i915: avoid wait_for_atomic() in non-atomic host2guc_action() 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 Cc: Tvrtko Ursulin Cc: Chris Wilson Reviewed-by: Chris Wilson Signed-off-by: Tvrtko Ursulin Link: http://patchwork.freedesktop.org/patch/msgid/1467815411-21756-1-git-send-email-david.s.gordon@intel.com --- 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 bfc8bf672f2d..2112e029db6a 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 -- 2.20.1