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

[Paulo Zanoni]

2013/7/24 Chris Wilson <chris at chris-wilson.co.uk>:
> 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.

Just to clarify: why not write(iir, 0xffffffff) twice to save the 2 reads?


> -Chris
>
> --
> Chris Wilson, Intel Open Source Technology Centre



-- 
Paulo Zanoni