linux_dsm_epyc7002/Documentation/hwmon/it87

Kernel driver it87
==================

Supported chips:
  * IT8705F
    Prefix: 'it87'
    Addresses scanned: from Super I/O config space (8 I/O ports)
    Datasheet: Publicly available at the ITE website
               http://www.ite.com.tw/
  * IT8712F
    Prefix: 'it8712'
    Addresses scanned: I2C 0x2d
                       from Super I/O config space (8 I/O ports)
    Datasheet: Publicly available at the ITE website
               http://www.ite.com.tw/
  * IT8716F
    Prefix: 'it8716'
    Addresses scanned: from Super I/O config space (8 I/O ports)
    Datasheet: Publicly available at the ITE website
               http://www.ite.com.tw/product_info/file/pc/IT8716F_V0.3.ZIP
  * IT8718F
    Prefix: 'it8718'
    Addresses scanned: from Super I/O config space (8 I/O ports)
    Datasheet: Publicly available at the ITE website
               http://www.ite.com.tw/product_info/file/pc/IT8718F_V0.2.zip
               http://www.ite.com.tw/product_info/file/pc/IT8718F_V0%203_(for%20C%20version).zip
  * SiS950   [clone of IT8705F]
    Prefix: 'it87'
    Addresses scanned: from Super I/O config space (8 I/O ports)
    Datasheet: No longer be available

Authors:
    Christophe Gauthron <chrisg@0-in.com>
    Jean Delvare <khali@linux-fr.org>


Module Parameters
-----------------

* update_vbat: int

  0 if vbat should report power on value, 1 if vbat should be updated after
  each read. Default is 0. On some boards the battery voltage is provided
  by either the battery or the onboard power supply. Only the first reading
  at power on will be the actual battery voltage (which the chip does
  automatically). On other boards the battery voltage is always fed to
  the chip so can be read at any time. Excessive reading may decrease
  battery life but no information is given in the datasheet.

* fix_pwm_polarity int

  Force PWM polarity to active high (DANGEROUS). Some chips are
  misconfigured by BIOS - PWM values would be inverted. This option tries
  to fix this. Please contact your BIOS manufacturer and ask him for fix.

Description
-----------

This driver implements support for the IT8705F, IT8712F, IT8716F,
IT8718F and SiS950 chips.

These chips are 'Super I/O chips', supporting floppy disks, infrared ports,
joysticks and other miscellaneous stuff. For hardware monitoring, they
include an 'environment controller' with 3 temperature sensors, 3 fan
rotation speed sensors, 8 voltage sensors, and associated alarms.

The IT8712F and IT8716F additionally feature VID inputs, used to report
the Vcore voltage of the processor. The early IT8712F have 5 VID pins,
the IT8716F and late IT8712F have 6. They are shared with other functions
though, so the functionality may not be available on a given system.
The driver dumbly assume it is there.

The IT8718F also features VID inputs (up to 8 pins) but the value is
stored in the Super-I/O configuration space. Due to technical limitations,
this value can currently only be read once at initialization time, so
the driver won't notice and report changes in the VID value. The two
upper VID bits share their pins with voltage inputs (in5 and in6) so you
can't have both on a given board.

The IT8716F, IT8718F and later IT8712F revisions have support for
2 additional fans. They are not yet supported by the driver.

The IT8716F and IT8718F, and late IT8712F and IT8705F also have optional
16-bit tachometer counters for fans 1 to 3. This is better (no more fan
clock divider mess) but not compatible with the older chips and
revisions. For now, the driver only uses the 16-bit mode on the
IT8716F and IT8718F.

Temperatures are measured in degrees Celsius. An alarm is triggered once
when the Overtemperature Shutdown limit is crossed.

Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
triggered if the rotation speed has dropped below a programmable limit. When
16-bit tachometer counters aren't used, fan readings can be divided by
a programmable divider (1, 2, 4 or 8) to give the readings more range or
accuracy. With a divider of 2, the lowest representable value is around
2600 RPM. Not all RPM values can accurately be represented, so some rounding
is done.

Voltage sensors (also known as IN 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. All voltage
inputs can measure voltages between 0 and 4.08 volts, with a resolution of
0.016 volt. The battery voltage in8 does not have limit registers.

The VID lines (IT8712F/IT8716F/IT8718F) encode the core voltage value:
the voltage level your processor should work with. This is hardcoded by
the mainboard and/or processor itself. It is a value in volts.

If an alarm triggers, it will remain triggered until the hardware register
is read at least once. 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 IT87xx only updates its values each 1.5 seconds; reading it more often
will do no harm, but will return 'old' values.

To change sensor N to a thermistor, 'echo 2 > tempN_type' where N is 1, 2,
or 3. To change sensor N to a thermal diode, 'echo 3 > tempN_type'.
Give 0 for unused sensor. Any other value is invalid. To configure this at
startup, consult lm_sensors's /etc/sensors.conf. (2 = thermistor;
3 = thermal diode)

The fan speed control features are limited to manual PWM mode. Automatic
"Smart Guardian" mode control handling is not implemented. However
if you want to go for "manual mode" just write 1 to pwmN_enable.