With no current tools yet identified, I thought I'd see if I could
manually change a trip point temp and type.
From /sys/class/thermal/thermal_zone0 I tried:
$ echo -n 40 > trip_point_1_temp
bash: trip_point_1_temp: Permission denied
$ echo -n active > trip_point_1_type
bash: trip_point_1_temp: Permission denied
I tried the same commands with sudo, with the same results.
Some things in /sys are meant to be read-only, but my understanding is
that the thermal_zone attributes should be writable.
Anyone know why this happens?
On 6/4/2014 1:25 PM, John Hupp wrote:
Further research shows that the use of /proc/acpi/thermal_zone has
been deprecated for some time. The new location is /sys/class/thermal.
I have not found any specific reference about the current state of
usage of /proc/acpi/fan, but from some reading and kernel.org (below),
I think it is probably deprecated as well.
But at least on the first point, many important reference pages are
outdated, such as https://wiki.ubuntu.com/DebuggingACPI and
https://01.org/linux-acpi/documentation/debug-how-isolate-linux-acpi-issues
(at the Intel Open Source Technology Center).
The current kernel-level documentation is at
https://www.kernel.org/doc/Documentation/thermal, and that's helpful
reading to get some idea of what the contents of /sys/class/thermal mean.
But what we need is something current that identifies user-space tools
and explains how to use them. Acpitool seems like the first
candidate, if it properly supports the current implementation. Its
homepage is given in Synaptic as
http://freeunix.dyndns.org:8088/site2/acpitool.shtml, but that site no
longer exists. Acpitool also installs acpid, and the homepage for
that is given as http://www.tedfelix.com/linux/acpid-netlink.html, but
that now redirects to http://sourceforge.net/p/acpid2. I had a look at
the wiki there, but saw nothing that helps for this purpose.
I installed acpitool just to test-drive it. 'acpitool -e' reports
everything, but it shows Fan and Thermal info as <not available> . It
also reports concerning Show_CPU_Info: "could not read
/proc/acpi/processor/. Make sure your kernel has ACPI processor
support enabled."
So it seems apparent that acpitool has not been properly or fully
updated for the kernel implementation of acpi in kernel version 2.7
(actually 2.6-something).
------------------------------------------------------------------------
Concerning my Lenovo, booting into Windows I see in Device Manager an
ACPI Thermal Zone and a number of other ACPI-related devices.
My initial conclusion when I saw that the Lenovo BIOS shows no thermal
management settings was that Lenovo didn't want people fiddling with
them and chose not to expose them. Now I think that thermal
management via the BIOS and SMM is not their provision. Rather, their
provision is thermal management via ACPI, governed in the operating
system.
On 6/1/2014 1:25 PM, John Hupp wrote:
I posted some of this material in the thread "Lubuntu: acerhdf.conf,"
but am starting a new thread that better reflects what I'm trying to
work out.
According to my current understanding, fans may be controlled by:
1) BIOS/UEFI
2) Bus signalling to PWM controllers governing fans [the lm-sensors
package does this]
3) System Management Mode (SMM) [the i8kutils package does this for
many Dell laptops]
4) ACPI
The above is undoubtedly only a rough description that lacks
precision, but AFAIK it describes well enough the avenues to solutions.
BIOS/UEFI - For this purpose I am working with a Lenovo 3000 C200
laptop flashed to the latest available version. Its BIOS exposes no
power/thermal management settings. I have heard of Windows programs
that allow reading and even editing of BIOS settings, and I thought
it would be useful to at least know what the hidden BIOS thermal
management settings were. Even better if I could edit them via
Linux. I found dmidecode, biosdecode and the smbios-utils suite, but
none of them could report, much less edit, the thermal management
settings. The coreboot.org project is a BIOS-replacement project,
but support is motherboard specific, the list is short, and my model
is not on the list. There are also some vendor-specific Linux BIOS
tools, but these all seem to be just for flashing the BIOS. So
unless I have missed something, it seems like that avenue comes to a
dead end.
lm-sensors - It discovers a sensor for the CPU, loads the coretemp
module, and reports that temperature. But pwmconfig reports "There
are no pwm-capable sensor modules installed." And the lm-sensors
documentation notes in a couple places that it won't work on most
laptops because they lack PWM controllers, and "you have to use acpi
instead." So that's also a dead end.
i8kutils - Many or most Dell laptops are reported to lack not only
PWM controllers but also support for ACPI fan control, so i8kutils
uses a different method, SMM, to control the fans. But the package
aims to support only Dell laptops, and seems to rely on knowledge of
specific motherboard architectures. Another dead end for my purposes.
ACPI - https://wiki.ubuntu.com/DebuggingACPI has the following:
------------------------------------------------------------------------
*Fan Issues *****
These usually relate to the fan spinning too often or too fast.
Another indication may be that the temperature remains high even when
the fans are spinning.
1. Determine if the system has ACPI-based fan control
*
if */proc/acpi/fan* is empty and
*/proc/acpi/thermal_zone/*/trip_points* has no active trip
points (those starting with "AC") then there is no ACPI-based
fan control on your system
2. If the system does have an ACPI-based fan control try booting
with kernel parameter options listed above
------------------------------------------------------------------------
On this laptop, neither /proc/acpi/fan nor
/proc/acpi/thermal_zone/*/trip_points even exist.
But /sys/class/thermal/thermal_zone0 has cdev0_trip_point,
cdev1_trip_point, trip_point_0_temp, trip_point_1_temp,
trip_point_0_type, trip_point_1_type all exist.
Dmidecode or biosdecode reported that the laptop supports ACPI, so
the question may be whether it supports ACPI fan control in particular.
I don't my Linux fundamentals regarding the purposes of /proc and
/sys, but have I just confirmed that this laptop has no ACPI fan
control support, or could it be that trip_points are supported from
more than one location?
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