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- Kernel driver adt7473
- ======================
- Supported chips:
- * Analog Devices ADT7473
- Prefix: 'adt7473'
- Addresses scanned: I2C 0x2C, 0x2D, 0x2E
- Datasheet: Publicly available at the Analog Devices website
- Author: Darrick J. Wong
- Description
- -----------
- This driver implements support for the Analog Devices ADT7473 chip family.
- The LM85 uses the 2-wire interface compatible with the SMBUS 2.0
- specification. Using an analog to digital converter it measures three (3)
- temperatures and two (2) voltages. It has three (3) 16-bit counters for
- measuring fan speed. There are three (3) PWM outputs that can be used
- to control fan speed.
- A sophisticated control system for the PWM outputs is designed into the
- LM85 that allows fan speed to be adjusted automatically based on any of the
- three temperature sensors. Each PWM output is individually adjustable and
- programmable. Once configured, the ADT7473 will adjust the PWM outputs in
- response to the measured temperatures without further host intervention.
- This feature can also be disabled for manual control of the PWM's.
- Each of the measured inputs (voltage, temperature, fan speed) has
- corresponding high/low limit values. The ADT7473 will signal an ALARM if
- any measured value exceeds either limit.
- The ADT7473 samples all inputs continuously. The driver will not read
- the registers more often than once every other second. Further,
- configuration data is only read once per minute.
- Special Features
- ----------------
- The ADT7473 have a 10-bit ADC and can therefore measure temperatures
- with 0.25 degC resolution. Temperature readings can be configured either
- for twos complement format or "Offset 64" format, wherein 63 is subtracted
- from the raw value to get the temperature value.
- The Analog Devices datasheet is very detailed and describes a procedure for
- determining an optimal configuration for the automatic PWM control.
- Hardware Configurations
- -----------------------
- The ADT7473 chips have an optional SMBALERT output that can be used to
- signal the chipset in case a limit is exceeded or the temperature sensors
- fail. Individual sensor interrupts can be masked so they won't trigger
- SMBALERT. The SMBALERT output if configured replaces the PWM2 function.
- Configuration Notes
- -------------------
- Besides standard interfaces driver adds the following:
- * PWM Control
- * pwm#_auto_point1_pwm and pwm#_auto_point1_temp and
- * pwm#_auto_point2_pwm and pwm#_auto_point2_temp -
- point1: Set the pwm speed at a lower temperature bound.
- point2: Set the pwm speed at a higher temperature bound.
- The ADT7473 will scale the pwm between the lower and higher pwm speed when
- the temperature is between the two temperature boundaries. PWM values range
- from 0 (off) to 255 (full speed). Fan speed will be set to maximum when the
- temperature sensor associated with the PWM control exceeds temp#_max.
- Notes
- -----
- The NVIDIA binary driver presents an ADT7473 chip via an on-card i2c bus.
- Unfortunately, they fail to set the i2c adapter class, so this driver may
- fail to find the chip until the nvidia driver is patched.
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