Re: 2.6.19: ACPI reports AC not present after resume from STD

Rafael J. Wysocki
2007-02-25T10:24:42Z

On Sunday, 25 February 2007 00:26, Andrey Borzenkov wrote:
> On Суббота 24 февраля 2007, Rafael J. Wysocki wrote:
> > Hi,
> >
> > On Saturday, 24 February 2007 10:55, Andrey Borzenkov wrote:
> > > On Вторник 13 февраля 2007, Andrey Borzenkov wrote:
> > > > On Четверг 07 декабря 2006, Lebedev, Vladimir P wrote:
> > > > > Please register new bug, attach acpidump and dmesg.
> > > >
> > > > http://bugzilla.kernel.org/show_bug.cgi?id=7995
> > > >
> > > > regards
> > >
> > > Well, this starts looking like ACPI is not at fault.
> > >
> > > When reporting AC state ACPI just reads contents of system memory (I
> > > presume it gets updated by BIOS/ACPI when AC state changes). It looks
> > > like this memory area is restored during resume from STD. I updated
> > > mentioned bug report with more detailed description. Now if someone could
> > > suggest a way to catch if specific physical address gets saved/restored
> > > this would finally explain it.
> >
> > First, if you want the reserved memory areas to be left alone by swsusp,
> > you need to mark them as 'nosave'. On x86_64 this is done by the function
> > e820_mark_nosave_range() in arch/x86_64/kernel/e820.c that can be ported to
> > i386 with no problems. However, we haven't found that very useful, so far,
> > since no one has ever reported any problems with the current approach,
> > which is to save and restore them.
> >
>
> Well, the following proof of concept patch fixes this issue for me. Please
> notice that original version of e820_mark_nosave_range() could fail to
> exclude some areas due to alignment issues (exactly what happened to me on
> first try) so it still can explain your problem too.

Great job, thanks for the patch! It looks good, so I'm going to forward it for
merging.

I'll also change the x86_64 version to use PFN_UP and PFN_DOWN.

Greetings,
Rafael