From bcbdb6d01150dcc1769ddc9baaaf7f102f27f919 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Wed, 27 Apr 2016 09:02:01 +0100 Subject: [PATCH] drm/i915: Protect gen7 irq_seqno_barrier with uncore lock Faced with sporadic machine hangs on gen7, that mimic the issue of concurrent writes to the same cacheline and seem to start with commit 9b9ed3093613 (drm/i915: Remove forcewake dance from seqno/irq barrier on legacy gen6+), let us restore the spinlock around the mmio read. Fixes: 9b9ed3093613 (drm/i915: Remove forcewake dance from seqno/irq...) Signed-off-by: Chris Wilson Cc: Mika Kuoppala Link: http://patchwork.freedesktop.org/patch/msgid/1461744121-27051-1-git-send-email-chris@chris-wilson.co.uk Tested-by: Mika Kuoppala Reviewed-by: Mika Kuoppala --- drivers/gpu/drm/i915/intel_ringbuffer.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c index 66f69cdd1d36..d6756ce6a586 100644 --- a/drivers/gpu/drm/i915/intel_ringbuffer.c +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c @@ -1577,6 +1577,8 @@ pc_render_add_request(struct drm_i915_gem_request *req) static void gen6_seqno_barrier(struct intel_engine_cs *engine) { + struct drm_i915_private *dev_priv = engine->dev->dev_private; + /* Workaround to force correct ordering between irq and seqno writes on * ivb (and maybe also on snb) by reading from a CS register (like * ACTHD) before reading the status page. @@ -1588,9 +1590,13 @@ gen6_seqno_barrier(struct intel_engine_cs *engine) * the write time to land, but that would incur a delay after every * batch i.e. much more frequent than a delay when waiting for the * interrupt (with the same net latency). + * + * Also note that to prevent whole machine hangs on gen7, we have to + * take the spinlock to guard against concurrent cacheline access. */ - struct drm_i915_private *dev_priv = engine->dev->dev_private; + spin_lock_irq(&dev_priv->uncore.lock); POSTING_READ_FW(RING_ACTHD(engine->mmio_base)); + spin_unlock_irq(&dev_priv->uncore.lock); } static u32 -- 2.20.1