RELENG_8: amdtemp module and newer CPUs not working. MFC?

[Jeremy Chadwick]

On Wed, Feb 20, 2013 at 10:29:05PM -0800, Don Lewis wrote:
> On 17 Feb, Torfinn Ingolfsen wrote:
> > Hello,
> > I'm running FreeBSD 8.3-stable on a machine with an AMD A8-5600K cpu.
> > tingo at kg-quiet$ uname -a
> > FreeBSD kg-quiet.kg4.no 8.3-STABLE FreeBSD 8.3-STABLE #2: Fri Jan  4 19:18:15 CET 2013 
> >     root at kg-quiet.kg4.no:/usr/obj/usr/src/sys/GENERIC  amd64
> > tingo at kg-quiet$ dmesg | grep CPU | head -1
> > CPU: AMD A8-5600K APU with Radeon(tm) HD Graphics    (3618.02-MHz K8-class CPU)
> > 
> > Unfortunately, the amdtemp.ko module doesn't work:
> > tingo at kg-quiet$ kldstat | grep temp
> > 10    1 0xffffffff8123e000 f0f      amdtemp.ko
> > tingo at kg-quiet$ sysctl dev.amdtemp
> > sysctl: unknown oid 'dev.amdtemp'
> > 
> > Based on a thread[1] on the forums, amdtemp.c from -CURRENT work.
> > But it doesn't compile under FreeBSD 8.3-stable:
> 
> Updating amdtemp is on my TODO list.  It has some issues even on
> -CURRENT.  This is kind of far down my priority list because on most of
> my AMD machines, I can also get the temperature without amdtemp:
> 
> % sysctl hw.acpi.thermal.tz0.temperature
> hw.acpi.thermal.tz0.temperature: 30.0C

There's an implication in your statement here, so I want to clarify for
readers (as the author of sysutils/bsdhwmon):

acpi_thermal(4) does not necessarily "tie in" to an on-die DTS within
the CPU.  Your motherboards and CPUs (both matter! (e.g. for Intel CPUs,
see PECI (not a typo)) may offer this tie-in, but such is not the case
for many people.  I tend to find ACPI thermal zones used in laptops and
very rarely anywhere else.

acpi_thermal(4) may return temperatures from zones that are mapped to
readings from Super I/O chips or dedicated H/W monitoring ICs (such as
ones provided by Nuvuton/Winbond, LM, ITE, ADT, etc.).  It all depends
on how the BIOSes ACPI tables are written/what maps to what.

Such ICs DO NOT have anything to do with the on-die DTS which both
amdtemp(4) and coretemp(4) use -- instead, these chips use external
thermistors which may be placed anywhere on the motherboard (such as
under the CPU socket, or wherever the manufacturer chooses (and more
often than not, does not document)).

My point: under the CPU thermistor != within the CPU DTS.  They measure
two different things, and are not guaranteed to be even remotely
similar.  I can show proof of this (a very large delta between Core i5
core DTSes and an on-board IT87xxx) if requested.

-- 
| Jeremy Chadwick                                   jdc at koitsu.org |
| UNIX Systems Administrator                http://jdc.koitsu.org/ |
| Mountain View, CA, US                                            |
| Making life hard for others since 1977.             PGP 4BD6C0CB |