[deliverable/linux.git] / Documentation / hwmon / adt7473

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 ADT7473 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 four (4) 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
ADT7473 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.

Configuration Notes
-------------------

Besides standard interfaces driver adds the following:

* PWM Control

* pwm#_auto_point1_pwm and temp#_auto_point1_temp and
* pwm#_auto_point2_pwm and temp#_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.
Commit	Line	Data
57df46d6 DW	1	Kernel driver adt7473
	2	======================
	3
	4	Supported chips:
	5	* Analog Devices ADT7473
	6	Prefix: 'adt7473'
	7	Addresses scanned: I2C 0x2C, 0x2D, 0x2E
	8	Datasheet: Publicly available at the Analog Devices website
	9
	10	Author: Darrick J. Wong
	11
	12	Description
	13	-----------
	14
	15	This driver implements support for the Analog Devices ADT7473 chip family.
	16
c73c556c	17	The ADT7473 uses the 2-wire interface compatible with the SMBUS 2.0
57df46d6	18	specification. Using an analog to digital converter it measures three (3)
c73c556c	19	temperatures and two (2) voltages. It has four (4) 16-bit counters for
57df46d6 DW	20	measuring fan speed. There are three (3) PWM outputs that can be used
	21	to control fan speed.
	22
	23	A sophisticated control system for the PWM outputs is designed into the
c73c556c	24	ADT7473 that allows fan speed to be adjusted automatically based on any of the
57df46d6 DW	25	three temperature sensors. Each PWM output is individually adjustable and
	26	programmable. Once configured, the ADT7473 will adjust the PWM outputs in
	27	response to the measured temperatures without further host intervention.
	28	This feature can also be disabled for manual control of the PWM's.
	29
	30	Each of the measured inputs (voltage, temperature, fan speed) has
	31	corresponding high/low limit values. The ADT7473 will signal an ALARM if
	32	any measured value exceeds either limit.
	33
	34	The ADT7473 samples all inputs continuously. The driver will not read
	35	the registers more often than once every other second. Further,
	36	configuration data is only read once per minute.
	37
	38	Special Features
	39	----------------
	40
	41	The ADT7473 have a 10-bit ADC and can therefore measure temperatures
	42	with 0.25 degC resolution. Temperature readings can be configured either
	43	for twos complement format or "Offset 64" format, wherein 63 is subtracted
	44	from the raw value to get the temperature value.
	45
	46	The Analog Devices datasheet is very detailed and describes a procedure for
	47	determining an optimal configuration for the automatic PWM control.
	48
57df46d6 DW	49	Configuration Notes
	50	-------------------
	51
	52	Besides standard interfaces driver adds the following:
	53
	54	* PWM Control
	55
c73c556c DW	56	* pwm#_auto_point1_pwm and temp#_auto_point1_temp and
c73c556c DW	57	* pwm#_auto_point2_pwm and temp#_auto_point2_temp -
57df46d6 DW	58
	59	point1: Set the pwm speed at a lower temperature bound.
	60	point2: Set the pwm speed at a higher temperature bound.
	61
	62	The ADT7473 will scale the pwm between the lower and higher pwm speed when
	63	the temperature is between the two temperature boundaries. PWM values range
241937b8 DW	64	from 0 (off) to 255 (full speed). Fan speed will be set to maximum when the
241937b8 DW	65	temperature sensor associated with the PWM control exceeds temp#_max.
57df46d6 DW	66
	67	Notes
	68	-----
	69
	70	The NVIDIA binary driver presents an ADT7473 chip via an on-card i2c bus.
	71	Unfortunately, they fail to set the i2c adapter class, so this driver may
	72	fail to find the chip until the nvidia driver is patched.