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docs: hwmon: add max31760 documentation
Adding documentation for max31760 fan speed controller
Signed-off-by: Ibrahim Tilki <Ibrahim.Tilki@analog.com>
Link: https://lore.kernel.org/r/20220910171945.48088-3-Ibrahim.Tilki@analog.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
authored by
Ibrahim Tilki
and committed by
Guenter Roeck
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Documentation/hwmon/index.rst
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Documentation/hwmon/max31760.rst
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Documentation/hwmon/max31760.rst
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.. SPDX-License-Identifier: GPL-2.0-or-later
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Kernel driver max31760
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======================
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Supported chips:
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* Analog Devices MAX31760
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Prefix: 'max31760'
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Addresses scanned: none
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Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX31760.pdf
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Author: Ibrahim Tilki <Ibrahim.Tilki@analog.com>
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Description
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-----------
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The MAX31760 integrates temperature sensing along with precision PWM fan
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control. It accurately measures its local die temperature and the remote
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temperature of a discrete diode-connected transistor, such as a 2N3906,
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or a thermal diode commonly found on CPUs, graphics processor units (GPUs),
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and other ASICs. Multiple temperature thresholds, such as local
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high/overtemperature (OT) and remote high/overtemperature, can be set by an
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I2C-compatible interface. Fan speed is controlled based on the temperature
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reading as an index to a 48-byte lookup table (LUT) containing
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user-programmed PWM values. The flexible LUT-based architecture enables
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the user to program a smooth nonlinear fan speed vs. temperature transfer
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function to minimize acoustic fan noise. Two tachometer inputs allow
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measuring the speeds of two fans independently. When the local or remote
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OT threshold is exceeded, the SHDN pin is asserted low and can be used to
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shut down the system. A dedicated ALERT pin reports that either a local or
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remote high-temperature threshold has been exceeded.
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Temperature measurement range: from -55°C to 125°C
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Temperature Resolution: 11 Bits, ±0.125°C
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Please refer how to instantiate this driver: Documentation/i2c/instantiating-devices.rst
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Lookup table for auto fan control
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---------------------------------
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========= =================================
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LUT Index Name
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========= =================================
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1 PWM value for T < +18°C
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2 PWM value for +18°C ≤ T < +20°C
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3 PWM value for +20°C ≤ T < +22°C
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... ...
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47 PWM value for +108°C ≤ T < +110°C
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48 PWM value for T ≥ +110°C
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========= =================================
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Sysfs entries
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-------------
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=============================== =================================================================================
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fan[1-2]_input Fan speed (in RPM)
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fan[1-2]_enable Enable fan readings and fan fault alarms
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fan[1-2]_fault Fan fault status
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temp[1-2]_label "Remote" and "Local" temperature channel labels
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temp[1-2]_input Temperature sensor readings (in millidegrees Celsius)
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temp1_fault Remote temperature sensor fault status
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temp[1-2]_max Temperature max value. Asserts "ALERT" pin when exceeded
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temp[1-2]_max_alarm Temperature max alarm status
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temp[1-2]_crit Temperature critical value. Asserts "SHDN" pin when exceeded
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temp[1-2]_crit_alarm Temperature critical alarm status
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pwm1 PWM value for direct fan control
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pwm1_enable 1: direct fan control, 2: temperature based auto fan control
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pwm1_freq PWM frequency in hertz
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pwm1_auto_channels_temp Temperature source for auto fan control. 1: temp1, 2: temp2, 3: max(temp1, temp2)
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pwm1_auto_point[1-48]_pwm PWM value for LUT point
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pwm1_auto_point_temp_hyst Temperature hysteresis for auto fan control. Can be either 2000mC or 4000mC
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=============================== =================================================================================