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Change-Id: I8a9ee2aea93cd29c52c847d0ce33091a73ae6afe
diff --git a/Documentation/hwmon/gl518sm b/Documentation/hwmon/gl518sm
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+Kernel driver gl518sm
+=====================
+
+Supported chips:
+ * Genesys Logic GL518SM release 0x00
+ Prefix: 'gl518sm'
+ Addresses scanned: I2C 0x2c and 0x2d
+ * Genesys Logic GL518SM release 0x80
+ Prefix: 'gl518sm'
+ Addresses scanned: I2C 0x2c and 0x2d
+ Datasheet: http://www.genesyslogic.com/
+
+Authors:
+ Frodo Looijaard <frodol@dds.nl>,
+ Kyösti Mälkki <kmalkki@cc.hut.fi>
+ Hong-Gunn Chew <hglinux@gunnet.org>
+ Jean Delvare <jdelvare@suse.de>
+
+Description
+-----------
+
+IMPORTANT:
+
+For the revision 0x00 chip, the in0, in1, and in2 values (+5V, +3V,
+and +12V) CANNOT be read. This is a limitation of the chip, not the driver.
+
+This driver supports the Genesys Logic GL518SM chip. There are at least
+two revision of this chip, which we call revision 0x00 and 0x80. Revision
+0x80 chips support the reading of all voltages and revision 0x00 only
+for VIN3.
+
+The GL518SM implements one temperature sensor, two fan rotation speed
+sensors, and four voltage sensors. It can report alarms through the
+computer speakers.
+
+Temperatures are measured in degrees Celsius. An alarm goes off while the
+temperature is above the over temperature limit, and has not yet dropped
+below the hysteresis limit. The alarm always reflects the current
+situation. Measurements are guaranteed between -10 degrees and +110
+degrees, with a accuracy of +/-3 degrees.
+
+Rotation speeds are reported in RPM (rotations per minute). An alarm is
+triggered if the rotation speed has dropped below a programmable limit. In
+case when you have selected to turn fan1 off, no fan1 alarm is triggered.
+
+Fan readings can be divided by a programmable divider (1, 2, 4 or 8) to
+give the readings more range or accuracy. Not all RPM values can
+accurately be represented, so some rounding is done. With a divider
+of 2, the lowest representable value is around 1900 RPM.
+
+Voltage sensors (also known as VIN sensors) report their values in volts.
+An alarm is triggered if the voltage has crossed a programmable minimum or
+maximum limit. Note that minimum in this case always means 'closest to
+zero'; this is important for negative voltage measurements. The VDD input
+measures voltages between 0.000 and 5.865 volt, with a resolution of 0.023
+volt. The other inputs measure voltages between 0.000 and 4.845 volt, with
+a resolution of 0.019 volt. Note that revision 0x00 chips do not support
+reading the current voltage of any input except for VIN3; limit setting and
+alarms work fine, though.
+
+When an alarm is triggered, you can be warned by a beeping signal through your
+computer speaker. It is possible to enable all beeping globally, or only the
+beeping for some alarms.
+
+If an alarm triggers, it will remain triggered until the hardware register
+is read at least once (except for temperature alarms). This means that the
+cause for the alarm may already have disappeared! Note that in the current
+implementation, all hardware registers are read whenever any data is read
+(unless it is less than 1.5 seconds since the last update). This means that
+you can easily miss once-only alarms.
+
+The GL518SM only updates its values each 1.5 seconds; reading it more often
+will do no harm, but will return 'old' values.