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[20/32] drm/i915: Replace manual barrier() with READ_ONCE() in HWS accessor

Message ID 1449833608-22125-21-git-send-email-chris@chris-wilson.co.uk (mailing list archive)
State New, archived
Headers show

Commit Message

Chris Wilson Dec. 11, 2015, 11:33 a.m. UTC
When reading from the HWS page, we use barrier() to prevent the compiler
optimising away the read from the volatile (may be updated by the GPU)
memory address. This is more suited to READ_ONCE(); make it so.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 drivers/gpu/drm/i915/intel_ringbuffer.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
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Patch

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 7ad06cbef6be..a35c17106f4b 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -416,8 +416,7 @@  intel_read_status_page(struct intel_engine_cs *ring,
 		       int reg)
 {
 	/* Ensure that the compiler doesn't optimize away the load. */
-	barrier();
-	return ring->status_page.page_addr[reg];
+	return READ_ONCE(ring->status_page.page_addr[reg]);
 }
 
 static inline void