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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
This commit is contained in:
Chris Wilson 2016-04-09 10:57:57 +01:00
parent 0d317ce99e
commit 5dd8e50c27
1 changed files with 2 additions and 4 deletions
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6
drivers/gpu/drm/i915/intel_ringbuffer.h
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@ -391,12 +391,10 @@ intel_flush_status_page(struct intel_engine_cs *engine, int reg)
}
static inline u32
intel_read_status_page(struct intel_engine_cs *engine,
int reg)
intel_read_status_page(struct intel_engine_cs *engine, int reg)
{
/* Ensure that the compiler doesn't optimize away the load. */
barrier();
return engine->status_page.page_addr[reg];
return READ_ONCE(engine->status_page.page_addr[reg]);
}
static inline void