Date:	Mon, 22 Sep 2008 10:59:59 +0300
From:	Maxim Levitsky <maximlevitsky@...il.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
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

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.

iommu? I don't think this mobo has it, it has PM965/GM965/GL960
(according to lspci)


Best regards,
	Maxim  Levitsky
> 
> Thanks,
> Rafael

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