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Date:      Thu, 26 Mar 2009 09:37:50 -0400
From:      John Baldwin <jhb@freebsd.org>
To:        freebsd-acpi@freebsd.org
Cc:        Daniel =?utf-8?q?Dvo=C5=99=C3=A1k?= <dandee@hellteam.net>
Subject:   Re: kern/108581: [sysctl] sysctl: hw.acpi.cpu.cx_lowest: Invalid argument
Message-ID:  <200903260937.51028.jhb@freebsd.org>
In-Reply-To: <20090325223914.4387eeae@gluon.draftnet>
References:  <200903200030.n2K0U3iG011009@freefall.freebsd.org> <20090325223914.4387eeae@gluon.draftnet>

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On Wednesday 25 March 2009 6:39:14 pm Bruce Cran wrote:
> On Fri, 20 Mar 2009 00:30:03 GMT
> Daniel Dvo=C5=99=C3=A1k <dandee@hellteam.net> wrote:
>=20
> > The following reply was made to PR kern/108581; it has been noted by
> > GNATS.
> >=20
> > From: =3D?UTF-8?Q?Daniel_Dvo=3DC5=3D99=3DC3=3DA1k?=3D <dandee@hellteam.=
net>
> > To: <bug-followup@FreeBSD.org>,
> > 	<lars.stokholm@gmail.com>
> > Cc: =20
> > Subject: Re: kern/108581: [sysctl] sysctl: hw.acpi.cpu.cx_lowest:
> > Invalid argument Date: Fri, 20 Mar 2009 01:01:51 +0100
> >=20
> >  This is a multi-part message in MIME format.
> > =20
> >  ------=3D_NextPart_000_0007_01C9A8F7.746C4190
> >  Content-Type: text/plain;
> >  	charset=3D"UTF-8"
> >  Content-Transfer-Encoding: quoted-printable
> > =20
> >  Hi acpi team,
> >  =3D20
> >  today I have installed fbsd 7.1R on one box with this relativly old =3D
> >  error and I was surprised about results .. it is the same:
> >  =3D20
> >  # uname -a
> >  FreeBSD X.Y.Z 7.1-RELEASE FreeBSD 7.1-RELEASE #0: Thu Jan  1
> > 14:37:25 =3D UTC 2009
> > root@logan.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  =3D i386
> > =20
> >  # sysctl dev.cpu.0.cx_supported
> >  dev.cpu.0.cx_supported: C1/0
> > =20
> >  # sysctl hw.acpi.cpu.cx_lowest=3D3DC1
> >  hw.acpi.cpu.cx_lowest: C1
> >  sysctl: hw.acpi.cpu.cx_lowest: Invalid argument
> >  =3D20
> >  # sysctl hw.acpi.cpu.cx_lowest=3D3DC0
> >  hw.acpi.cpu.cx_lowest: C1
> >  sysctl: hw.acpi.cpu.cx_lowest: Invalid argument
> >  =3D20
> >  # sysctl hw.acpi.cpu.cx_lowest=3D3DC1/0
> >  hw.acpi.cpu.cx_lowest: C1
> >  sysctl: hw.acpi.cpu.cx_lowest: Invalid argument
> > =20
> >  # dmesg -a | grep "acpi"
> >  acpi0: <ASUS P4S8X-X> on motherboard
> >  acpi0: Overriding SCI Interrupt from IRQ 9 to IRQ 20
> >  acpi0: [ITHREAD]
> >  acpi0: Power Button (fixed)
> >  acpi0: reservation of 0, a0000 (3) failed
> >  acpi0: reservation of 100000, ff00000 (3) failed
> >  acpi_timer0: <24-bit timer at 3.579545MHz> port 0xe408-0xe40b on
> > acpi0 acpi_button0: <Power Button> on acpi0
> >  pcib0: <ACPI Host-PCI bridge> port 0xcf8-0xcff on acpi0
> >  atkbdc0: <Keyboard controller (i8042)> port 0x60,0x64 irq 1 on acpi0
> >  cpu0: <ACPI CPU> on acpi0
> >  hw.acpi.cpu.cx_lowest:
> >  hw.acpi.cpu.cx_lowest
>=20
> I think I've found the problem and have updated the PR kern/108581
> (http://www.freebsd.org/cgi/query-pr.cgi?pr=3Dkern/108581). The global
> cpu_cx_count was being initialized to 0 in acpi_cpu_startup
> (in /sys/dev/acpica/acpi_cpu.c) but code below it appears to assume that
> it's been intialized to 3 because it only sets it if it's higher than
> the current CPU supports - that is, cpu_cx_count should reflect the
> highest Cx state that all CPUs support.
>=20
> There's also a bug in the _CST section just below it; I think the line:
>=20
> if (sc->cpu_cx_count > cpu_cx_count)
>=20
> should be
>=20
> if (sc->cpu_cx_count < cpu_cx_count)

No, the code is doing things differently on purpose (though I'm not complet=
ely=20
sure why).  For _CST it sets cpu_cx_count to the maximum Cx level supported=
=20
by any CPU in the system.  For non-_CST it sets it to the maximum Cx level=
=20
supported by all CPUs in the system.  I think it is correct for cpu_cx_coun=
t=20
to always start at 0 and only be bumped up to a higher setting.  Setting it=
=20
to 3 would be very wrong for the _CST case as I've seen CPUs that support C=
4.

Note that C1 _always_ exists as it is simply the "hlt" instruction that has=
=20
existed since the 8086.  Only C2+ require power-saving extension support in=
=20
the CPU, so cpu_cx_count should always end up >=3D 1.  It would be interest=
ing=20
if you could add some debug printfs to print out the values that=20
acpi_cpu_generic_cx_probe() computes for 'sc->cpu_cx_count' (sysctl dev.cpu=
=20
could be useful for this) as well as all changes to the 'cpu_cx_count' glob=
al=20
variable.

=2D-=20
John Baldwin



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