From mboxrd@z Thu Jan  1 00:00:00 1970
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Subject: Re: Is e_powersaver safe to auto-load?
Date: Wed, 22 Feb 2012 01:13:39 +0000
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To: Ben Hutchings <ben@decadent.org.uk>
Cc: Dave Jones <davej@redhat.com>, cpufreq@vger.kernel.org, Andi Kleen <ak@linux.intel.com>


> The e_powersaver driver comes with a dire warning in Kconfig help:
>
>      VIA C7 Enhanced PowerSaver (DANGEROUS)
>
>      This adds the CPUFreq driver for VIA C7 processors.  However, th=
is driver
>      does not have any safeguards to prevent operating the CPU out of=
 spec
>      and is thus considered dangerous.  Please use the regular ACPI c=
pufreq
>      driver, enabled by CONFIG_X86_ACPI_CPUFREQ.
>
> Following the bug report<http://bugs.debian.org/566208>, Debian's
> cpufrequtils init script was changed to stop loading it.  The driver =
was
> later disabled in Debian kernel configurations.  Rafa=C5=82 appears t=
o have
> made it somewhat safer since then, but the help text has not been
> changed.
>
> Since commit fa8031aefec0cf7ea6c2387c93610d99d9659aa2 ('cpufreq: Add
> support for x86 cpuinfo auto loading v4') the driver will be auto-loa=
ded
> on some systems.  If it is still dangerous then it should surely not =
be
> auto-loaded.  But if it is now believed to be safe then the help text
> should be updated to say so.
>
> Ben.
>
Hello again,

Mainboard in question is VIA Epia SN10000EG rev. A1. I have access to i=
t
now. I've tested it briefly for a couple of hours and it seems to work =
fine with
3.2 kernel. I will let you know if more extensive testing will give dif=
ferent result.

Rafa=C5=82

eps: Detected VIA Model A C7
eps: Current voltage =3D 1004mV
eps: Current multiplier =3D 10
eps: Highest voltage =3D 1004mV
eps: Highest multiplier =3D 10
eps: Lowest voltage =3D 956mV
eps: Lowest multiplier =3D 8
eps: ACPI limit 1.0GHz