linux-kernel - [PATH V2 5/5] Package Level Thermal Control and Power Limit Notification: pkgtemp doc

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Message-Id: <1280343653-26380-6-git-send-email-fenghua.yu@intel.com>
Date:	Wed, 28 Jul 2010 12:00:53 -0700
From:	"Fenghua Yu" <fenghua.yu@...el.com>
To:	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"H Peter Anvin" <hpa@...or.com>, "Len Brown" <lenb@...nel.org>,
	"Guenter Roeck" <guenter.roeck@...csson.com>,
	"Chen Gong" <gong.chen@...ux.intel.com>,
	"Jean Delvare" <khali@...ux-fr.org>,
	"Huaxu Wan" <huaxu.wan@...el.com>
Cc:	"linux-kernel" <linux-kernel@...r.kernel.org>,
	"lm-sensors" <lm-sensors@...sensors.org>,
	Fenghua Yu <fenghua.yu@...el.com>
Subject: [PATH V2 5/5] Package Level Thermal Control and Power Limit Notification: pkgtemp doc

From: Fenghua Yu <fenghua.yu@...el.com>

Document for package level thermal hwmon driver.

Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
Reviewed-by: Len Brown <len.brown@...el.com>
Reviewed-by: Guenter Roeck <guenter.roeck@...csson.com>
---
 Documentation/hwmon/pkgtemp |   36 ++++++++++++++++++++++++++++++++++++
 1 files changed, 36 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/hwmon/pkgtemp

diff --git a/Documentation/hwmon/pkgtemp b/Documentation/hwmon/pkgtemp
new file mode 100644
index 0000000..c8e1fb0
--- /dev/null
+++ b/Documentation/hwmon/pkgtemp
@@ -0,0 +1,36 @@
+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.
-- 
1.7.2

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