linux-kernel - Re: 2.6.25-rc7/8: Another resume regression

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Date:	Mon, 07 Apr 2008 11:51:38 -0400
From:	Mark Lord <lkml@....ca>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	LKML <linux-kernel@...r.kernel.org>, Adrian Bunk <bunk@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, david-b@...bell.net,
	oliver@...kum.org, Alan Stern <stern@...land.harvard.edu>,
	Dave Airlie <airlied@...ux.ie>,
	Jesse Barnes <jesse.barnes@...el.com>,
	Pavel Machek <pavel@....cz>
Subject: Re: 2.6.25-rc7/8: Another resume regression

Rafael J. Wysocki wrote:
> On Saturday, 5 of April 2008, Mark Lord wrote:
>> Mark Lord wrote:
>>> Hi,
>>>
>>> Okay, USB now works fine on resume after fixing the iaa_watchdog issue.
>>>
>>> But twice now, once before that fix, and again just a minute ago,
>>> my machine has failed completely to resume after suspend-to-RAM.
>>>
>>> Again, resume here is 100% reliable in 2.6.24 and earlier.
>>>
>>> Symptoms: the usual:
>>>
>>>  -- 2.6.25-rc8 (and -rc7 earlier), plus USB fix.
>>>  -- not reproduceable on demand.
>>>  -- black screen of death -- no backlight, no kernel messages.
>>>  -- no hard drive activity.
>>>  -- no alt-sysrq-anything.
>>>  -- 5 second hold of the power button to poweroff and then recover.
>>>
>>> Not much info to go on, but it's worth knowing there's an issue here 
>>> somewhere.
>> ..
>>
>> Mmmm... Now that 2.6.25-rc* is usable here, there's another symptom
>> that's been happening regularly enough that it's got to be a regression
>> of some sort.
>>
>> This machine has an ATI X1400 video card, which doesn't work with any
>> open source X server that I know of.  Maybe latest RadeonHD would work
>> but it didn't when I tried it in January.
>>
>> So I'm using the ATI binary fglrx X server, but without their kernel module,
>> so no 3D acceleration (fine.. only affects Google Earth, really).
>>
>> Now.. on 2.6.25, after a suspend/resume cycle (or three), the framebuffer
>> frequently starts going wonky.  "snowy" pixels appear, and stay.
>> Just a moment ago here, the entire background changed to zebra stripes.
>>
>> And so on..  Peculiar stuff.
>>
>> I'm wondering if something to do with video mode switching,
>> or video register save/restore, has changed since 2.6.24.
>> Because it's broken in 2.6.25, yet works fine in all earlier kernels.
> 
> Yes, that's probably related.
> 
> However, I'm unable to reproduce the breakage.  If you can do that, it would
> probably help a lot if you identified the commit causing that to happen.
..

Well, it would help then if you identified the commits which hacked
at the video mode switching.  Then I can revert those and see what happens.
There's probably not many commits there, and since it doesn't do it consistently
(and sometimes the machine just doesn't resume at all with 2.6.25), 
it is tricky to bisect.

Works perfectly in 2.6.24, though, which is what I'm now running again.
 
Thanks
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