Commit 5dd8e50c authored Apr 09, 2016 by Chris Wilson

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

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>
Link: http://patchwork.freedesktop.org/patch/msgid/1460195877-20520-5-git-send-email-chris@chris-wilson.co.uk

parent 0d317ce9

drivers/gpu/drm/i915/intel_ringbuffer.h

+2 −4

Original line number	Original line	Diff line number	Diff line
	@@ -391,12 +391,10 @@ intel_flush_status_page(struct intel_engine_cs *engine, int reg)
	}		}

	static inline u32		static inline u32
	intel_read_status_page(struct intel_engine_cs *engine,		intel_read_status_page(struct intel_engine_cs *engine, int reg)
	int reg)
	{		{
	/* Ensure that the compiler doesn't optimize away the load. */		/* Ensure that the compiler doesn't optimize away the load. */
	barrier();		return READ_ONCE(engine->status_page.page_addr[reg]);
	return engine->status_page.page_addr[reg];
	}		}

	static inline void		static inline void