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

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Date:	Tue, 13 May 2014 03:30:39 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	"Zheng, Lv" <lv.zheng@...el.com>
Cc:	"RobertBMoore@...puserve.com" <RobertBMoore@...puserve.com>,
	"Thomas Renninger (trenn@...e.de)" <trenn@...e.de>,
	Oswald Buddenhagen <ossi@....org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
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@...ysocki.net]
> > 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!

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