linux-kernel - Re: I need some serious help to debug suspend to ram problem

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Date:	Sun, 21 Sep 2008 20:56:26 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Maxim Levitsky <maximlevitsky@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	Alan Stern <stern@...land.harvard.edu>
Subject: Re: I need some serious help to debug suspend to ram problem

On Sunday, 21 of September 2008, Maxim Levitsky wrote:
> Maxim Levitsky wrote:
> > Rafael J. Wysocki wrote:
> >> On Saturday, 20 of September 2008, Maxim Levitsky wrote:
> >>> Hi,
> >>>
> >>> I hit a dead end when trying to understand why my notebook can't 
> >>> resume from suspend to ram
> >>> if this is done two times a row.
> >>>
> >>> Single suspend/resume cycle works almost perfectly (beep that goes 
> >>> through the sound card is muted... no morse code for me... :-(
> >>>
> >>> )
> >>>
> >>> I compiled a minimal kernel (absolutely nothing but disk drivers, all 
> >>> experimental option like nohz
> >>> turned off)
> >>>
> >>> But I had to turn SMP, since without it system won't resume first 
> >>> time I suspend it.
> >>> (How could this affect suspend?)
> >>
> >> It could if the system is 64-bit.  In which case please have a look at
> >> http://bugzilla.kernel.org/show_bug.cgi?id=11237
> >>
> >>> With SMP and minimal kernel (of course  no closed drivers), I get 
> >>> same behavior,
> >>> first resume works second hangs.
> >>>
> >>> I then added some debug code to real mode wakeup code, I put there in 
> >>> first
> >>> place instructions, that will save some magic value to rtc (to alarm
> >>> registers that I know are preserved during boot cycle), and I 
> >>> discovered   sad thing that first time bios does pass control to 
> >>> linux, but second time
> >>> (when it hangs), it doesn't.
> >>>
> >>> I tried to update bios, and I got same results.
> >>>
> >>> Of course it does work with that @#$%^& OS
> >>
> >> So we're doing something wrong.  Please try the appended patch.
> > Thanks a lot, but this didn't help.
> > 
> > It still has same pattern, first suspend/resume works perfectly, second 
> > suspend/resume hangs hard.
> > It always happens like this, first resume always work (unless I turn off 
> > smp in kernel (I test this again), or reserve all low memory)
> > 
> > Also note that if I suspend the system to ram, resume, and then suspend 
> > to disk, then I can suspend to ram and resume, it seems that
> > 
> > on suspend to ram cycle somehow arms BIOS or something else, so second 
> > resume in a row doesn't work.
> > 
> > I run 32 bit kernel here, this is a long story (this bios doesn't turn 
> > fan on when running 64-bit version, I could update it, and I know that 
> > fan issue is fixed there, but new bios introduces bigger bug, namely it 
> > makes fan to run almost always regardless of 32/64 type of os.
> > And it doesn't fix this suspend/resume issue, I tested this. I could 
> > start/stop fan manually with a script, but this could fail, and maybe I 
> > will do so someday.)
> > 
> > The bugzilla seems to be unrelated here, since bios does pass control 
> > there, but corrupts memory.
> > Here I also have seen that bios corrupts memory, but everything resumes 
> > fine first time, and on second time,
> > bios doesn't pass control (I put set of instructions in beginning of 
> > wakeup real mode assembly file, no page tables, GDT/LDT are used there)
> 
> I did same test for kernel without SMP, yes it hangs on first resume, but bios
> does pass control to linux, so while this is a minor bug, it is unrelated.

Still, I'd be interested in debugging this one too, if possible.  That may be
easier too. ;-)

> I also tested noapic, pci=nommconf. No luck.
> 
> Pattern is always the same, first resume works always, second doesn't.
> It is sad since first resume is almost perfect (when I have free time I need to look at sound codec datasheet
> and fix few issues there, anyways here alsa has few issues, all this is trivial, I already fixed all issues with desktop
> which has a sigmatel codec)

If you have more than 2 GB of RAM, you can try iommu=soft .

I guess that all of the /sys/power/pm_test tests are passed?

Thanks,
Rafael
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