xref: /openbmc/linux/Documentation/hwmon/max31785.rst (revision 7ebd8b66)

Kernel driver max31785
======================

Supported chips:

  * Maxim MAX31785, MAX31785A

    Prefix: 'max31785' or 'max31785a'

    Addresses scanned: -

    Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX31785.pdf

Author: Andrew Jeffery <andrew@aj.id.au>

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

The Maxim MAX31785 is a PMBus device providing closed-loop, multi-channel fan
management with temperature and remote voltage sensing. Various fan control
features are provided, including PWM frequency control, temperature hysteresis,
dual tachometer measurements, and fan health monitoring.

For dual-rotor configurations the MAX31785A exposes the second rotor tachometer
readings in attributes fan[5-8]_input. By contrast the MAX31785 only exposes
the slowest rotor measurement, and does so in the fan[1-4]_input attributes.

Usage Notes
-----------

This driver does not probe for PMBus devices. You will have to instantiate
devices explicitly.

Sysfs attributes
----------------

======================= =======================================================
fan[1-4]_alarm		Fan alarm.
fan[1-4]_fault		Fan fault.
fan[1-8]_input		Fan RPM. On the MAX31785A, inputs 5-8 correspond to the
			second rotor of fans 1-4
fan[1-4]_target		Fan input target

in[1-6]_crit		Critical maximum output voltage
in[1-6]_crit_alarm	Output voltage critical high alarm
in[1-6]_input		Measured output voltage
in[1-6]_label		"vout[18-23]"
in[1-6]_lcrit		Critical minimum output voltage
in[1-6]_lcrit_alarm	Output voltage critical low alarm
in[1-6]_max		Maximum output voltage
in[1-6]_max_alarm	Output voltage high alarm
in[1-6]_min		Minimum output voltage
in[1-6]_min_alarm	Output voltage low alarm

pwm[1-4]		Fan target duty cycle (0..255)
pwm[1-4]_enable		0: Full-speed
			1: Manual PWM control
			2: Automatic PWM (tach-feedback RPM fan-control)
			3: Automatic closed-loop (temp-feedback fan-control)

temp[1-11]_crit		Critical high temperature
temp[1-11]_crit_alarm	Chip temperature critical high alarm
temp[1-11]_input	Measured temperature
temp[1-11]_max		Maximum temperature
temp[1-11]_max_alarm	Chip temperature high alarm
======================= =======================================================