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Commit a3159864 authored by Fenghua Yu's avatar Fenghua Yu Committed by H. Peter Anvin
Browse files

x86, hwmon: Package Level Thermal/Power: pkgtemp documentation 



Document for package level thermal hwmon driver.

Signed-off-by: default avatarFenghua Yu <fenghua.yu@intel.com>
LKML-Reference: <1280448826-12004-6-git-send-email-fenghua.yu@intel.com>
Reviewed-by: default avatarLen Brown <len.brown@intel.com>
Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent 0199114c

Documentation/hwmon/pkgtemp

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Kernel driver pkgtemp

======================



Supported chips:

  * Intel family

    Prefix: 'pkgtemp'

    CPUID:

    Datasheet: Intel 64 and IA-32 Architectures Software Developer's Manual

               Volume 3A: System Programming Guide



Author: Fenghua Yu



Description

-----------



This driver permits reading package level temperature sensor embedded inside

Intel CPU package. The sensors can be in core, uncore, memory controller, or

other components in a package. The feature is first implemented in Intel Sandy

Bridge platform.



Temperature is measured in degrees Celsius and measurement resolution is

1 degree C. Valid temperatures are from 0 to TjMax degrees C, because the actual

value of temperature register is in fact a delta from TjMax.



Temperature known as TjMax is the maximum junction temperature of package.

We get this from MSR_IA32_TEMPERATURE_TARGET. If the MSR is not accessible,

we define TjMax as 100 degrees Celsius. At this temperature, protection

mechanism will perform actions to forcibly cool down the package. Alarm

may be raised, if the temperature grows enough (more than TjMax) to trigger

the Out-Of-Spec bit. Following table summarizes the exported sysfs files:



temp1_input	  - Package temperature (in millidegrees Celsius).

temp1_max        - All cooling devices should be turned on.

temp1_crit	  - Maximum junction temperature (in millidegrees Celsius).

temp1_crit_alarm - Set when Out-of-spec bit is set, never clears.

		    Correct CPU operation is no longer guaranteed.