hwmon: New driver for Analog Devices ADT7473 sensor chip

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).

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.

	  This driver can also be built as a module. If so, the module

	  will be called adt7470.

config SENSORS_ADT7473

	tristate "Analog Devices ADT7473"

	depends on I2C && EXPERIMENTAL

	help

	  If you say yes here you get support for the Analog Devices

	  ADT7473 temperature monitoring chips.

	  This driver can also be built as a module. If so, the module

	  will be called adt7473.

config SENSORS_K8TEMP

	tristate "AMD Athlon64/FX or Opteron temperature sensor"

	depends on X86 && PCI && EXPERIMENTAL

obj-$(CONFIG_SENSORS_ADM9240)	+= adm9240.o

obj-$(CONFIG_SENSORS_ADS7828)	+= ads7828.o

obj-$(CONFIG_SENSORS_ADT7470)	+= adt7470.o

obj-$(CONFIG_SENSORS_ADT7473)	+= adt7473.o

obj-$(CONFIG_SENSORS_APPLESMC)	+= applesmc.o

obj-$(CONFIG_SENSORS_AMS)	+= ams/

obj-$(CONFIG_SENSORS_ATXP1)	+= atxp1.o