RE: [PATCH] ACPICA: Revert "ACPICA: Add option to favor 32-bit FADT addresses."

[Zheng, Lv]

Hi, Rafael

> From: Rafael J. Wysocki [mailto:rjw@xxxxxxxxxxxxx]
> Sent: Tuesday, May 13, 2014 9:31 AM
> To: Zheng, Lv
> Cc: RobertBMoore@xxxxxxxxxxxxxx; Thomas Renninger (trenn@xxxxxxx); Oswald Buddenhagen; ACPI Devel Maling List; Linux
> Kernel Mailing List
> Subject: Re: [PATCH] ACPICA: Revert "ACPICA: Add option to favor 32-bit FADT addresses."
> 
> On Tuesday, May 13, 2014 01:05:59 AM Zheng, Lv wrote:
> > Hi,
> >
> > > From: Rafael J. Wysocki [mailto:rjw@xxxxxxxxxxxxx]
> > > Sent: Tuesday, May 13, 2014 8:09 AM
> > >
> > > On Monday, May 12, 2014 08:51:36 AM Zheng, Lv wrote:
> > > > Hi, Rafael
> > > >
> > > > I checked the bug.
> > > >
> > > > The dmesg of the kernel without the bisected commit:
> > > > [    0.000000] ACPI BIOS Warning (bug): Incorrect checksum in table [XSDT] - 0xA0, should be 0xC9 (20140214/tbprint-218)
> > > > [    0.000000] ACPI Warning: 32/64 FACS address mismatch in FADT - two FACS tables! (20140214/tbfadt-395)
> > > > [    0.000000] ACPI BIOS Warning (bug): 32/64X FACS address mismatch in FADT - 0xCF661F40/0x00000000CF667E40, using 32
> > > (20140214/tbfadt-522)
> > > >
> > > > The dmesg of the kernel with the bisected commit:
> > > > [    0.000000] ACPI BIOS Warning (bug): Incorrect checksum in table [XSDT] - 0xA0, should be 0xC9 (20131218/tbprint-214)
> > > > [    0.000000] ACPI BIOS Warning (bug): 32/64X FACS address mismatch in FADT: 0xCF661F40/0x00000000CF667E40, using 64-bit
> > > address (20131218/tbfadt-271)
> > > >
> > > > This is the purpose of the bisected commit.
> > > > According to the link below:
> > > > http://bugs.acpica.org/show_bug.cgi?id=885
> > > > And Windows documentation:
> > > > http://download.microsoft.com/download/5/b/9/5b97017b-e28a-4bae-ba48-174cf47d23cd/CPA002_WH06.ppt
> > > > We believe 64-bit addresses should be used by default so that new features can be enabled according to the public knowledge
> of
> > > Windows Vista+ behavior.
> > > > For old Windows, it's hard for us to guess, we should wait for the reports and add quirks for them.
> > > >
> > > > Thus this commit is not wrong, it shouldn't be reverted.
> > >
> > > It is wrong, because it breaks a system that worked without it.
> > >
> > > It's *that* simple.
> >
> > For this commit, we knew there would be systems broken.
> > And was prepared to add quirks for them.
> > The quirks are not there just because we rely on end users to report.
> >
> > >
> > > And either you have a fix for that (which is not a quirk, because there may be
> > > more machines like that), or we have to revert it.
> > >
> > > > Though this platform is newer than vista, we still should offer a quirk mechanism
> > > > for it as a quick fix:
> > >
> > > We didn't need a quirk for it before, though.
> >
> > But according to BZ885, we need more quirks for other machines before.
> > For example, ThinkPad 40e and ThinkPad 51e reported in the BZ885.
> >
> > >
> > > So really, I'm reverting it.
> >
> > OK.
> > I'll first try to figure out the cause of the issue that is happening to Intel DP45SG.
> > And then try this approach again in a smarter way that is more tolerant torward the possible regressions.
> 
> Great, thanks!

If you have troubles in reverting things.
I can offer one line patch to revert the functionality of the bisected commit back to the original behavior.
In acpixf.h, make acpi_gbl_use32_bit_fadt_address to TRUE can be a fix.
I'll ask for the test on the bugzilla.

Thanks and best regards
-Lv

> 
> --
> I speak only for myself.
> Rafael J. Wysocki, Intel Open Source Technology Center.