Kernel driver max31760

Supported chips:

Author: Ibrahim Tilki <Ibrahim.Tilki@analog.com>

Description

The MAX31760 integrates temperature sensing along with precision PWM fan control. It accurately measures its local die temperature and the remote temperature of a discrete diode-connected transistor, such as a 2N3906, or a thermal diode commonly found on CPUs, graphics processor units (GPUs), and other ASICs. Multiple temperature thresholds, such as local high/overtemperature (OT) and remote high/overtemperature, can be set by an I2C-compatible interface. Fan speed is controlled based on the temperature reading as an index to a 48-byte lookup table (LUT) containing user-programmed PWM values. The flexible LUT-based architecture enables the user to program a smooth nonlinear fan speed vs. temperature transfer function to minimize acoustic fan noise. Two tachometer inputs allow measuring the speeds of two fans independently. When the local or remote OT threshold is exceeded, the SHDN pin is asserted low and can be used to shut down the system. A dedicated ALERT pin reports that either a local or remote high-temperature threshold has been exceeded.

Temperature measurement range: from -55°C to 125°C

Temperature Resolution: 11 Bits, ±0.125°C

Please refer how to instantiate this driver: How to instantiate I2C devices

Lookup table for auto fan control

LUT Index

Name

1

PWM value for T < +18°C

2

PWM value for +18°C ≤ T < +20°C

3

PWM value for +20°C ≤ T < +22°C

…

…

47

PWM value for +108°C ≤ T < +110°C

48

PWM value for T ≥ +110°C

Sysfs entries

fan[1-2]_input

Fan speed (in RPM)

fan[1-2]_enable

Enable fan readings and fan fault alarms

fan[1-2]_fault

Fan fault status

temp[1-2]_label

“Remote” and “Local” temperature channel labels

temp[1-2]_input

Temperature sensor readings (in millidegrees Celsius)

temp1_fault

Remote temperature sensor fault status

temp[1-2]_max

Temperature max value. Asserts “ALERT” pin when exceeded

temp[1-2]_max_alarm

Temperature max alarm status

temp[1-2]_crit

Temperature critical value. Asserts “SHDN” pin when exceeded

temp[1-2]_crit_alarm

Temperature critical alarm status

pwm1

PWM value for direct fan control

pwm1_enable

1: direct fan control, 2: temperature based auto fan control

pwm1_freq

PWM frequency in hertz

pwm1_auto_channels_temp

Temperature source for auto fan control. 1: temp1, 2: temp2, 3: max(temp1, temp2)

pwm1_auto_point[1-48]_pwm

PWM value for LUT point

pwm1_auto_point_temp_hyst

Temperature hysteresis for auto fan control. Can be either 2000mC or 4000mC