[Intel-gfx] [PATCH 04/15] drm/i915: really clear the IIR registers

[Chris Wilson]

On Tue, Jul 23, 2013 at 07:33:44PM -0300, Paulo Zanoni wrote:
> From: Paulo Zanoni <paulo.r.zanoni at intel.com>
> 
> As written on our docs, the IIR registers are capable of storing 2
> interrupts, so if we write once to them there's no guarantee they will
> become zero. So on this patch we write to the register, read to check
> if it's zero, and then write again in case it's needed.
> 
> Also replace I915_WRITE(iir, I915_READ(iir)) with I915_WRITE(iir,
> 0xffffffff), and then move the POSTING_READs on IER because we removed
> the extra IIR read.

Just write(read(iir)) twice and add a comment why.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre