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<div class="moz-cite-prefix">Hi John,<br>
This is an intense e-mail. I think you should post this online
somewhere, and track your progress. I think there could be other
people who are looking to hack around on other hardware, that
might benefit from your in-depth study on this.<br>
<br>
I am throughly impressed with the volume on information here.<br>
<br>
I don't have any advice where to turn next, however. The only
thing I'd suggest testing is a few other distros to see if the fan
control works better on another one. Some distros have their
kernel set up differently, and have packages Ubuntu doesn't... so
you never know. It has helped me to track down a problem or two
in the past. Puppy is a good one to try, as they make a few
version from different distros like Ubuntu and Slackware... and it
is very small to download and doesn't require any special install
to dual boot. You can copy the files out of the ISO and boot from
GRUB (which is handy if you have no optical drive or USB booting)<br>
<br>
Definitely let us know when you figure this out. And please add
your solution to wiki.ubuntu.com in some appropriate place. You
might try asking some specific questions in askubuntu or
ubuntuforums.<br>
<br>
<br>
On 06/17/2014 02:56 PM, John Hupp wrote:<br>
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<div class="moz-cite-prefix">This is a fresh attempt to summarize
what I've been looking at the past few weeks, with a nod to
Phill W's request. People with more specialized expertise will
likely want to correct this in any number of ways. Better
knowledge is very much welcome.<br>
<br>
Fan control, especially on laptops, which was my central
interest, is part of the larger topic of thermal management,
which includes active and passive methods. Fan control is the
usual active method. Passive methods include several
technologies for throttling devices, and these methods have
varying effects on performance. Thermal management has
historically focused on the CPU, but has broadened to embrace
the GPU, hard drive, LCD screen, and the entire enclosure. This
has become increasingly important as form factors have shrunk.<br>
<br>
Thermal management for a desktop is usually an easier
proposition because the heat sources are not as crammed
together, because it's easier to add fans if needed, and because
the thermal management technologies most commonly used in a
desktop are, in general, better supported, and they are more
exposed by the OEM's.<br>
<br>
The situation for laptops is, in general, the opposite of
everything just said about desktops.<br>
<br>
<b>Some further orientation and outline of the various
approaches</b>:<br>
<br>
BIOS (presumably similar for UEFI): This is the first thing to
look at. The BIOS likely sets up some thermal management, and
may present simple or sophisticated controls in its interface.
In other cases the OEM has decided not to present any
user-configurable controls there whatsoever. When an OS has
booted, the BIOS may relinquish all or part of thermal control
to it (commonly via ACPI). But it may continue to exercise
control through SMM (System Management Mode), which temporarily
suspends processing by the OS in a way that is transparent to
it, and runs some SMM BIOS code. By definition then, it can be
difficult to know what, if anything is controlled by SMM. And
SMM is platform-dependent, so there doesn't seem to be a
standards-based way for developers to write code that works
across whatever makes and models use SMM.<br>
<br>
ACPI (Advanced Configuration and Power Interface): This is the
successor to PNP configuration and APM power management. Under
ACPI, power management is no longer the responsibility of the
BIOS via APM, but of the OS. ACPI is closely related to OSPM
(Operating System-directed configuration and Power Management),
which has been described as a system implementing ACPI. Proper
functioning under ACPI requires support by the hardware, the
BIOS, and the OS. The ACPI BIOS loads some ACPI tables into
memory, the most prominent of which is the DSDT (Differentiated
System Description Table). These tables provide hardware
enumeration data and AML (ACPI Machine Language) bytecode. The
OS kernel uses an interpreter (ACPICA -- ACPI Component
Architecture) to run the bytecode and employ the data to set
everything up. [A development note: ACPI was merged into the
UEFI Forum in 2013.]<br>
<br>
ACPI and Sysfs: The state of the kernel is reflected to user
space via a sysfs, a virtual filesystem mounted at /sys. In
Windows-ish terms, this describes what device drivers are loaded
and what their settings are. But in addition to the original
device nodes that describe the kernel state most concisely,
there are also symlinks to many of the original device nodes,
set up in various /sys locations, serving various purposes. So
for thermal management purposes, one might be instructed to look
at the contents of /sys/class/thermal, but a number of the
folders there are symlinks to yet other /sys directories. Some
of the kernel parameters reflected at /sys are writable (or are
supposed to be, or were at one time).<br>
<br>
Hwmon - a sysfs extension: This extension to sysfs provides
alternate interfaces under /sys to report or control kernel
parameters that may also be represented elsewhere in /sys. But
some user applications are written such that they rely
exclusively on the hwmon interfaces.<br>
<br>
ACPI and Procfs - What is now accomplished for thermal
management purposes by the sysfs mounted at /sys, was previously
accomplished by the procfs mounted at /proc. So there is a lot
of documentation regarding, for instance, /proc/acpi/fan and
/proc/acpi/thermal_zone/*/trip_points (see <a
moz-do-not-send="true"
href="https://wiki.ubuntu.com/DebuggingACPI">https://wiki.ubuntu.com/DebuggingACPI</a>),
but that information is now obsolete.<br>
<br>
Generic Thermal Management Framework - Much of thermal policy or
decision-making has been handled in the OS by the kernel, but
exposed to some degree to user control via sysfs. The idea
under this framework is reduce the role the kernel plays to that
of a facilitator, and leave policy/decision-making to user-land
tools. But worth noting is that such user tools do not
fundamentally add to lower-level methods.<br>
<br>
<b>SOLUTIONS</b> (check the standard repositories first for any
additional packages you want to download)<br>
<br>
BIOS: Start here. This may be all you need to improve your fan
control. Sometimes an updated BIOS is required.<br>
<br>
lm-sensors + fancontrol (<a moz-do-not-send="true"
href="http://www.lm-sensors.org">http://www.lm-sensors.org</a>):
This solution explicitly relies on the hwmon interfaces of /sys,
and it only works with PWM (pulse-width modulated) fan
controllers, not with voltage-regulated controllers (and no, I
don't know why on either count). But its README says this:<br>
<blockquote>Laptops, on the other hand, rarely expose any
hardware monitoring chip. They often have some BIOS and/or
ACPI magic to get the CPU temperature value, but that's about
it. For such laptops, the lm-sensors package is of no use
(sensors-detect will not find anything), and you have to use
acpi instead.<br>
</blockquote>
ACPI - Editing/creating thermal trip points: Regarding thermal
management, you will see documentation that commands like these
should change the thermal trip point temperature:<br>
$ sudo sh -c "echo 75000 >
/sys/class/thermal/thermal_zone0/trip_point_1_temp"<br>
or<br>
$ echo 75000 | sudo tee trip_point_1_temp<br>
But this does not seem to be supported by recent kernels and
yielded "Permission denied" errors in my tests. I have seen
conflicting information on whether trip points should be
editable.<br>
Concerning laptops, there is this statement at <a
moz-do-not-send="true"
href="https://01.org/linux-acpi/documentation/debug-how-isolate-linux-acpi-issues">https://01.org/linux-acpi/documentation/debug-how-isolate-linux-acpi-issues</a>:<br>
"Most notebooks also use native fan control instead of ACPI.
There are, however, a couple of notable exceptions: HP/Compaq,
Acer, and Fujitsu-Siemens often use ACPI-based fan-control."<br>
<br>
ACPI - Overriding the DSDT table: There is documentation (e.g. <a
moz-do-not-send="true"
href="http://blog.michael.kuron-germany.de/2011/03/patching-dsdt-in-recent-linux-kernels-without-recompiling/">Patching
DSDT in recent Linux kernels without recompiling</a>) about
how to edit the DSDT table that the BIOS presents to the kernel,
and then direct the kernel to use the edited table. One wonders
about that as a method for creating/modifying ACPI thermal trip
points. I have not tried it. One source with more expertise
says that this *might* work, but notes that if a fan is
controlled by SMM, this may overrule something set up in ACPI.<br>
<br>
i8kutils (<a moz-do-not-send="true"
href="http://manpages.ubuntu.com/manpages/trusty/man1/i8kctl.1.html">i8kctl</a>
and <a moz-do-not-send="true"
href="http://manpages.ubuntu.com/manpages/trusty/man1/i8kmon.1.html">i8kmon</a>):
This relies on SMM, and as a platform-dependent solution, the
authors are aiming to support only Dell laptops. But this is
probably the best solution for those.<br>
<br>
thinkpad-acpi (<a moz-do-not-send="true"
href="http://www.thinkwiki.org/wiki/How_to_control_fan_speed">http://www.thinkwiki.org/wiki/How_to_control_fan_speed</a>):
This is an extension of the ACPI support provided by the
standard kernel. Note that it does not support all Lenovo
laptops. Lenovo 3000's, for instance, are not Thinkpads and are
not supported by this extension.<br>
<br>
Asus: See <a moz-do-not-send="true"
href="http://forum.notebookreview.com/asus/705656-fan-control-asus-prime-ux31-ux31a-ux32a-ux32vd.html">http://forum.notebookreview.com/asus/705656-fan-control-asus-prime-ux31-ux31a-ux32a-ux32vd.html</a>
and <a moz-do-not-send="true"
href="https://gist.github.com/felipec/6169047">https://gist.github.com/felipec/6169047</a>
and <a moz-do-not-send="true"
href="https://help.ubuntu.com/community/AsusZenbookPrime#Sensors_.28temps_.26_fans.29">https://help.ubuntu.com/community/AsusZenbookPrime#Sensors_.28temps_.26_fans.29</a>
as good starting points.<br>
<br>
Thermald: See the links following for information about the
thermal daemon new to 14.04. It is an implementation of the
Generic Thermal Management Framework. It controls cooling via <br>
- the Running Average Power Limit (RAPL) driver (Sandybridge
upwards)<br>
- the Intel P-state CPU frequency driver (Sandybridge upwards)<br>
- the CPU freq driver<br>
- the Intel PowerClamp driver<br>
- active or passive cooling devices as presented in sysfs (but
it cannot create any new devices; if there is no FAN device, it
will not control the fan)<br>
<a moz-do-not-send="true"
href="https://wiki.ubuntu.com/Kernel/PowerManagement/ThermalIssues">https://wiki.ubuntu.com/Kernel/PowerManagement/ThermalIssues</a><br>
<a moz-do-not-send="true"
href="http://manpages.ubuntu.com/manpages/trusty/en/man5/thermal-conf.xml.5.html">http://manpages.ubuntu.com/manpages/trusty/en/man5/thermal-conf.xml.5.html</a><br>
<a moz-do-not-send="true"
href="https://01.org/linux-thermal-daemon/documentation/introduction-thermal-daemon">https://01.org/linux-thermal-daemon/documentation/introduction-thermal-daemon</a><br>
<a moz-do-not-send="true"
href="http://www.linux.com/news/featured-blogs/200-libby-clark/721494-linux-thermal-daemon-monitors-and-controls-temperature-in-tablets-laptops">http://www.linux.com/news/featured-blogs/200-libby-clark/721494-linux-thermal-daemon-monitors-and-controls-temperature-in-tablets-laptops</a><br>
<br>
<b>MY CURRENT CASE</b><br>
<br>
I wanted the fan to start at a lower temperature on a Lenovo
3000 C200 laptop. <br>
<br>
The BIOS exposes no thermal settings. But someone who
previously made a serious attempt at this on a Lenovo 3000 N200
says that the fan is controlled by SMM. This makes sense, since
the fan trips at the same temperature in Windows or Lubuntu.
It's notable that active cooling is done via SMM, while passive
cooling is via ACPI.<br>
<br>
Lm-sensors: It does not find a PWM controller that it can work
with.<br>
<br>
ACPI: There are only two trip points defined, both passive, and
the lowest of them at 87C. There is no FAN device in
/sys/class/thermal, and attempts to modify trip point settings
resulted in "Permission denied." I still wonder if editing the
DSDT table might net me any gains, but I decided for the time
being not to invest any more time, especially with the prospect
that SMM would undo my work.<br>
<br>
Thinkpad-acpi: It does not support the Lenovo 3000.<br>
<br>
Thermald: I installed this with high hopes, but found out that
it cannot control a fan if an ACPI fan device does not already
exist. And since this laptop does not have a SandyBridge or
newer processor to take advantage of the RAPL or P-state
drivers, thermald does not bring much to the table that ACPI did
not already provide.<br>
<br>
Further recourse: The only measures I can imagine now are to
write something like i8kutils for this Lenovo platform. Or edit
the DSDT table just to see what happens. I say "imagine"
because I will very likely do neither! One source also
mentioned the prospect of controlling the embedded controller
for the fan via hwmon, but I haven't seen any details on how to
accomplish that apart from lm-sensors.<br>
<br>
A small bit of consolation: I recall that Speedfan regards 50C
as a good trip point, and thermald will try to keep the CPU
under 45C. But I have read that it's generally OK for laptops
to run somewhat hotter than desktops. This laptop fan kicks on
around 68C and seems to hold the line pretty well, so maybe the
thermal management is not as bad as I first thought.<br>
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<br>
<br>
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<br>
<pre class="moz-signature" cols="72">--
Regards</pre>
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