[Intel-gfx] [PATCH] drm/i915/ringbuffer: set force wake bit before reading ring register

[Chris Wilson]

On Wed, 10 Nov 2010 08:36:20 +0800, "Zou, Nanhai" <nanhai.zou at intel.com> wrote:
> >>-----Original Message-----
> >>From: Chris Wilson [mailto:chris at chris-wilson.co.uk]
> >>Sent: 2010年11月9日 18:50
> >>To: Zou, Nanhai; intel-gfx at lists.freedesktop.org; Zhao, Jian J
> >>Subject: RE: [PATCH] drm/i915/ringbuffer: set force wake bit before reading
> >>ring register
> >>
> >>On Tue, 9 Nov 2010 17:17:07 +0800, "Zou, Nanhai" <nanhai.zou at intel.com> wrote:
> >>
> >>> I have tested this patch with the read ring head from status page workaround
> >>patch reverted.
> >>> Seems it works on my SNB box.
> >>
> >>I needed to add a udelay(100) to i915_safe_read for my rev 8. Can you
> >>check if there is a recommended delay for FORCEWAKE?
> >>-Chris
> >>
> Dose a post read to FORCEWAKE help?

No, tried a POSTING_READ(FORCEWAKE) first and it wasn't until I added the
udelay() between the READ(FORCEWAKE) and the READ(reg) that it returned
the correct results in a single call.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre