Message-Id: <200809271515.50250.rjw@sisk.pl>
Date:	Sat, 27 Sep 2008 15:15:49 +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 Monday, 22 of September 2008, Maxim Levitsky wrote:
> Rafael J. Wysocki wrote:
> > 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 take a look at that.
> 
> > 
> >> 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?
> 
> Well, I didn't run /sys/power/pm_test. 
> But this system has rock solid suspend to disk, I use it always.

Please look at http://bugzilla.kernel.org/show_bug.cgi?id=11415 .

Perhaps you can add some information into it.

Thanks,
Rafael
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