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SubjectRe: I need some serious help to debug suspend to ram problem
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
>>> 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.

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)
> Best regards,
> Maxim Levitsky

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