Re: [PATCH 35/43] drm/i915: Move __raw_i915_read8() & co. into i915_drv.h

Chris Wilson
2015-09-18T18:33:54Z

On Fri, Sep 18, 2015 at 09:23:11PM +0300, Ville Syrjälä wrote:
> On Fri, Sep 18, 2015 at 06:42:17PM +0100, Chris Wilson wrote:
> > On Fri, Sep 18, 2015 at 08:03:48PM +0300, ville.syrjala@linux.intel.com wrote:
> > > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > >
> > > We have a few users of the raw register acces functions outside
> > > intel_uncore.c, so let's just move the functions into intel_drv.h.
> >
> > I would rather see those external users converted to
> > I915_READ_FW/I915_WRITE_FW etc. You will then, no doubt, want to convert
> > those _FW macro definitions over to the uncore set.
> >
> > Also due to how we write and post our accesses, the raw functions can be
> > the _relaxed variants.
>
> Hmm. I think the only difference with the relaxed vs. not would be
> potential compiler reordering of memory accesses vs. mmio. So if we
> start using the relaxed versions we may need to start sprinkling
> barriers around.

Yes. We have been working under that assumption (weak ordering of writes),
or at least I hope we all have been...
-Chris

--
Chris Wilson, Intel Open Source Technology Centre