[Intel-gfx] [PATCH] drm/i915: don't call swsci_setup on resume

[Chris Wilson]

On Thu, Feb 06, 2014 at 04:35:10PM +0100, Daniel Vetter wrote:
> On Thu, Feb 6, 2014 at 4:32 PM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > On Thu, Feb 06, 2014 at 01:19:48PM -0200, Paulo Zanoni wrote:
> >> From: Paulo Zanoni <paulo.r.zanoni at intel.com>
> >>
> >> This function is used to discover which swsci callbacks the machine
> >> supports. It calls swsci() 3 times, and usually takes a considerable
> >> number of milliseconds to finish.
> >>
> >> I don't see a reason for a change on the supported callbacks between
> >> boot and resume, so use the values retrieved at boot time forever,
> >> making resume a little bit faster.
> >
> > This looks unsafe following a hibernate resume where the system could
> > change around us. Across a suspend resume, you can argue that we do not
> > need to shootdown OpRegion (and not just swsci) at all.
> 
> See my other mail, but I think _init/_fini take care of all this. The
> only exception would be if the bios moves the opregion around, but
> that's only really possible if you update it or change your machine
> otherwise. Then you get both pieces anyway.

Exactly, that's why I think trusting the layout post hibernate is
danagerous.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre