linux-kernel - Re: [Intel-gfx] Linux 3.16-rc2

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Date:	Tue, 8 Jul 2014 10:35:05 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	Chris Wilson <chris@...is-wilson.co.uk>,
	Pavel Machek <pavel@....cz>,
	"intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Meyer <thomas@...3r.de>
Subject: Re: [Intel-gfx] Linux 3.16-rc2

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
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