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Date:	Sat, 24 Aug 2013 12:55:05 +0200
From:	Sedat Dilek <sedat.dilek@...il.com>
To:	Chris Wilson <chris@...is-wilson.co.uk>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	linux-next <linux-next@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	intel-gfx <intel-gfx@...ts.freedesktop.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: linux-next: Tree for Aug 21 [ screen corruption in graphical mode ]

On Fri, Aug 23, 2013 at 10:34 AM, Chris Wilson <chris@...is-wilson.co.uk> wrote:
> On Fri, Aug 23, 2013 at 10:04:37AM +0200, Sedat Dilek wrote:
>> On Fri, Aug 23, 2013 at 9:55 AM, Sedat Dilek <sedat.dilek@...il.com> wrote:
>> > On Thu, Aug 22, 2013 at 1:32 PM, Daniel Vetter <daniel.vetter@...ll.ch> wrote:
>> >> On Thu, Aug 22, 2013 at 1:30 PM, Daniel Vetter <daniel.vetter@...ll.ch> wrote:
>> >>> On Thu, Aug 22, 2013 at 1:13 PM, Sedat Dilek <sedat.dilek@...il.com> wrote:
>> >>>> dmesg (a lot of traces) and kernel-config attached.
>> >>>>
>> >>>> UXA causes still screen corruption.
>> >>>
>> >>> Hm, was only a slim chance that this patch would fix anything - I
>> >>> think you'd always see an oops when you'd hit this bug instead of just
>> >>> a bit of corruption.
>> >>
>> >> Ok, I think it's time to throw in the towel a bit. I've dropped
>> >>
>> >>
>> >> commit d46f1c3f1372e3a72fab97c60480aa4a1084387f
>> >> Author: Chris Wilson <chris@...is-wilson.co.uk>
>> >> Date:   Thu Aug 8 14:41:06 2013 +0100
>> >>
>> >>     drm/i915: Allow the GPU to cache stolen memory
>
> Hmm, wrong patch. Unless you have a good reason, you just want to drop
> the ringbuffers in stolen.
>
>> >> from my queue. I guess we can retry for 3.13 again.
>> >
>> > I am sorry to keep someone's work to be delayed, really.
>> > I would have liked to see this fixed (and I have spent some time on it).
>
> It's just a minor memory optimization (reclaiming less than a megabyte
> of system memory).
>
>> > Which patches did you exactly drop?
>> >
>>
>> Sorry for bombing you with question...
>>
>> I am trying latest Linus-tree HEAD with the drm-intel-nightly I made
>> my last testings.
>>
>> Are any of these TLB / x86-get_unmapped_area fixes of interested...
>> has any effects on the reported issue?
>
> It should not. Of concern is how the GPU views the world which has its
> own independent set of TLBs and mapping tables - and access to those
> should always be uncached from the CPU's perspective.
>
>> I still wonder what is the root-cause...
>> I mean if SNA is OK but UXA not and Linux graphics stack is that complex.
>> ( Can't say if user-space like unity isn't involved... ).
>
> All that userspace can affect here is the timing and inital contents of
> the framebuffer, everything else is controlled by the kernel. All the
> testing we have done so far imply that the kernel's view of the machine
> state is consistent with our expectations, but the display is doing
> something inexplicable.

Can this be a problem?

[ dmesg ]
[   27.949704] [drm] Wrong MCH_SSKPD value: 0x16040307
[   27.949708] [drm] This can cause pipe underruns and display issues.
[   27.949709] [drm] Please upgrade your BIOS to fix this.

- Sedat -
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