From 0da715ee60774401bea00dc71fca6fd1096c734a Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Mon, 20 Nov 2017 20:55:02 +0000 Subject: [PATCH] drm/i915: Disable semaphores on Sandybridge I should have admitted defeat long ago as there has been a rare but persistent error on Sandybridge where semaphore signaling did not propagate to the waiter, leading to a GPU hang. With the work on fence signaling for v4.9, the impact of using CPU driven signaling was greatly reduced wrt to the latency of GPU semaphores, though without logical rings support, the benefit of reordering work to avoid bubbles is not realised (i.e. as it stands fence signaling is just a slower, more costly version of HW semaphores; but works more consistently). As a rough indicator of the difference, with semaphores: Sequential (3 engines, 1 processes): average 5.470us per cycle [expected 4.988us] w/o semaphores: Sequential (3 engines, 1 processes): average 15.771us per cycle [expected 4.923us] In comparison, v3.4: with semaphores: Sequential (3 engines, 1 processes): average 16.066us per cycle [expected 11.842us] w/o semaphores: Sequential (3 engines, 1 processes): average 23.460us per cycle [expected 11.839us] Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=54226 #and 100+ dupes Signed-off-by: Chris Wilson Cc: Joonas Lahtinen Acked-by: Mika Kuoppala Reviewed-by: Joonas Lahtinen Link: https://patchwork.freedesktop.org/patch/msgid/20171120205504.21892-3-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/i915_gem.c | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index d470e10b2edd..d53bb8e872ba 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -4999,20 +4999,12 @@ out: bool intel_sanitize_semaphores(struct drm_i915_private *dev_priv, int value) { - if (INTEL_GEN(dev_priv) < 6) - return false; - - /* TODO: make semaphores and Execlists play nicely together */ - if (HAS_EXECLISTS(dev_priv)) + if (!IS_GEN7(dev_priv)) return false; if (value >= 0) return value; - /* Enable semaphores on SNB when IO remapping is off */ - if (IS_GEN6(dev_priv) && intel_vtd_active()) - return false; - return true; } -- 2.30.2