68 lines
2.5 KiB
Text
68 lines
2.5 KiB
Text
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Kernel driver adt7462
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======================
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Supported chips:
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* Analog Devices ADT7462
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Prefix: 'adt7462'
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Addresses scanned: I2C 0x58, 0x5C
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Datasheet: Publicly available at the Analog Devices website
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Author: Darrick J. Wong
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Description
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-----------
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This driver implements support for the Analog Devices ADT7462 chip family.
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This chip is a bit of a beast. It has 8 counters for measuring fan speed. It
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can also measure 13 voltages or 4 temperatures, or various combinations of the
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two. See the chip documentation for more details about the exact set of
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configurations. This driver does not allow one to configure the chip; that is
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left to the system designer.
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A sophisticated control system for the PWM outputs is designed into the ADT7462
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that allows fan speed to be adjusted automatically based on any of the three
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temperature sensors. Each PWM output is individually adjustable and
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programmable. Once configured, the ADT7462 will adjust the PWM outputs in
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response to the measured temperatures without further host intervention. This
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feature can also be disabled for manual control of the PWM's.
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Each of the measured inputs (voltage, temperature, fan speed) has
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corresponding high/low limit values. The ADT7462 will signal an ALARM if
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any measured value exceeds either limit.
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The ADT7462 samples all inputs continuously. The driver will not read
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the registers more often than once every other second. Further,
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configuration data is only read once per minute.
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Special Features
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----------------
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The ADT7462 have a 10-bit ADC and can therefore measure temperatures
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with 0.25 degC resolution.
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The Analog Devices datasheet is very detailed and describes a procedure for
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determining an optimal configuration for the automatic PWM control.
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The driver will report sensor labels when it is able to determine that
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information from the configuration registers.
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Configuration Notes
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-------------------
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Besides standard interfaces driver adds the following:
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* PWM Control
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* pwm#_auto_point1_pwm and temp#_auto_point1_temp and
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* pwm#_auto_point2_pwm and temp#_auto_point2_temp -
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point1: Set the pwm speed at a lower temperature bound.
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point2: Set the pwm speed at a higher temperature bound.
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The ADT7462 will scale the pwm between the lower and higher pwm speed when
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the temperature is between the two temperature boundaries. PWM values range
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from 0 (off) to 255 (full speed). Fan speed will be set to maximum when the
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temperature sensor associated with the PWM control exceeds temp#_max.
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