linux-kernel - Re: [ 32/37] drm/i915: correctly order the ring init sequence

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Message-ID: <1345388084.22400.3.camel@deadeye.wl.decadent.org.uk>
Date:	Sun, 19 Aug 2012 15:54:44 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Daniel Vetter <daniel.vetter@...ll.ch>
Cc:	Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Jani Nikula <jani.nikula@...el.com>,
	Yang Guang <guang.a.yang@...el.com>
Subject: Re: [ 32/37] drm/i915: correctly order the ring init sequence

On Sat, 2012-08-18 at 12:04 +0200, Daniel Vetter wrote:
> On Sat, Aug 18, 2012 at 1:29 AM, Herton Ronaldo Krzesinski
> <herton.krzesinski@...onical.com> wrote:
> > On Fri, Aug 17, 2012 at 04:03:15AM +0100, Ben Hutchings wrote:
> >> 3.2-stable review patch.  If anyone has any objections, please let me know.
> >>
> >> ------------------
> >>
> >> From: Daniel Vetter <daniel.vetter@...ll.ch>
> >>
> >> commit 0d8957c8a90bbb5d34fab9a304459448a5131e06 upstream.
> >>
> >> We may only start to set up the new register values after having
> >> confirmed that the ring is truely off. Otherwise the hw might lose the
> >> newly written register values. This is caught later on in the init
> >> sequence, when we check whether the register writes have stuck.
> >>
> >> Reviewed-by: Jani Nikula <jani.nikula@...el.com>
> >> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=50522
> >> Tested-by: Yang Guang <guang.a.yang@...el.com>
> >> Signed-off-by: Daniel Vetter <daniel.vetter@...ll.ch>
> >> Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
> > [...]
> >
> > With this commit on 3.2, i915 fails to initialize on a G41 based machine
> > I have here:
> >
> > [   36.894261] i915 0000:00:02.0: PCI INT A -> GSI 16 (level, low) -> IRQ 16
> > [   36.894265] i915 0000:00:02.0: setting latency timer to 64
> > [   36.933118] mtrr: type mismatch for d0000000,10000000 old: write-back new: write-combining
> > [   36.933121] [drm] MTRR allocation failed.  Graphics performance may suffer.
> > [   36.933467] i915 0000:00:02.0: irq 42 for MSI/MSI-X
> > [   36.933471] [drm] Supports vblank timestamp caching Rev 1 (10.10.2010).
> > [   36.933472] [drm] Driver supports precise vblank timestamp query.
> > [   36.933498] vgaarb: device changed decodes: PCI:0000:00:02.0,olddecodes=io+mem,decodes=io+mem:owns=io+mem
> > [   36.969669] [drm:init_ring_common] *ERROR* render ring initialization failed ctl 0001f001 head 00001074 tail 00000000 start 00001000
> > [   36.969763] vga_switcheroo: disabled
> > [   36.969765] [drm:i915_driver_load] *ERROR* failed to init modeset
> > [   36.987444] i915 0000:00:02.0: PCI INT A disabled
> > [   36.987453] i915: probe of 0000:00:02.0 failed with error -5
> >
> > Taking a look at it, I suspected of a timing issue, especially looking at
> > this commit, which isn't on 3.2:
> >
> > commit 18ef6f6c70a6cc36ee71e4a98a68901229
> > Author: Sean Paul <seanpaul@...omium.org>
> > Date:   Fri Mar 16 12:43:22 2012 -0400
> >
> >     drm/i915: Add wait_for in init_ring_common
> >
> > And picking it made the issue go away, so the extra delay helped and is needed
> > with 0d8957c8a90bbb5d34fab9a304459448a5131e06 applied here.
> 
> Good catch, I've forgotten to check whether all the recent ring_init
> patches have gone  through cc: stable. For the stable team, please
> pick up both patches:
> 
> f01db988ef6f6c70a6cc36ee71e4a98a68901229 and
> 0d8957c8a90bbb5d34fab9a304459448a5131e06
> 
> Note that all kernels that need f01db backported also need
> b7884eb45ec98c0d34c7f49005ae9d4b4b4e38f6 (to fix a regression
> introduce by the former).

3.2.y already had the second and third of these, but not f01db98
'drm/i915: Add wait_for in init_ring_common'.  So I've added that.

I don't have commit 18ef6f6c70a6cc36ee71e4a98a68901229 here, but I
assume it's a cherry-picked version as it has the same subject line.

Ben.

> Yeah, the ring init sequence is a fickle beast :( but I'm pretty sure
> with these three patches, stable kernels should be up to date and have
> all the latest fixes.
> 
> Yours, Daniel

-- 
Ben Hutchings
I say we take off; nuke the site from orbit.  It's the only way to be sure.

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