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[5/5] drm/i915: Replace manual barrier() with READ_ONCE() in HWS accessor

Message ID 1455623268-10023-6-git-send-email-chris@chris-wilson.co.uk (mailing list archive)
State New, archived
Headers show

Commit Message

Chris Wilson Feb. 16, 2016, 11:47 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>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
---
 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 e2b2dc2c2f49..231663a76387 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -403,8 +403,7 @@  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