Signed-off-by: Fenghua Yu <email@example.com>
Reviewed-by: Len Brown <firstname.lastname@example.org>
Signed-off-by: H. Peter Anvin <email@example.com>
(cherry picked from commit a3159864f2978bf2ace9cc787d73d315c98bbf9a)
diff --git a/Documentation/hwmon/pkgtemp b/Documentation/hwmon/pkgtemp
new file mode 100644
@@ -0,0 +1,36 @@
+Kernel driver pkgtemp
+ * Intel family
+ Prefix: 'pkgtemp'
+ Datasheet: Intel 64 and IA-32 Architectures Software Developer's Manual
+ Volume 3A: System Programming Guide
+Author: Fenghua Yu
+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
+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.
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