Re: Linux 3.16-rc2

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Jul 08, 2014 at 12:15:31AM +0200, Jiri Kosina wrote:
> On Mon, 7 Jul 2014, Chris Wilson wrote:
> 
> > > > this patch on top of v3.16-rc3-62-gd92a333 makes the resume from ram
> > > > regression go away on my machine:
> > > 
> > > Hm, we could conditionalize this hack on IS_G4X ... Chris, thoughts?
> > 
> > As different machines favour different w/a, I think the issue is mostly
> > timing related. It could be sequence of register writes, but we tried
> > different orders early on. The next experiment I guess would be to
> > insert small delays between each write to see if that helps. Or to write
> > each register twice.
> 
> I actually tried to introduce rather large delays between individual 
> I915_WRITE() calls in the ring initialization sequence a couple weeks ago 
> already, but it resulted in complete machine lockup (which is worse than 
> my usual symptoms) during resume. Therefore I probably lack the knowledge 
> of internal workings of the HW that would allow me to guess what the 
> reasonable timeout value should be.

Have you used msleep or udelay? The latter just spins the cpu and might be
less dangerous.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch