1Kernel driver adt7462
2=====================
3
4Supported chips:
5
6  * Analog Devices ADT7462
7
8    Prefix: 'adt7462'
9
10    Addresses scanned: I2C 0x58, 0x5C
11
12    Datasheet: Publicly available at the Analog Devices website
13
14Author: Darrick J. Wong
15
16Description
17-----------
18
19This driver implements support for the Analog Devices ADT7462 chip family.
20
21This chip is a bit of a beast.  It has 8 counters for measuring fan speed.  It
22can also measure 13 voltages or 4 temperatures, or various combinations of the
23two.  See the chip documentation for more details about the exact set of
24configurations.  This driver does not allow one to configure the chip; that is
25left to the system designer.
26
27A sophisticated control system for the PWM outputs is designed into the ADT7462
28that allows fan speed to be adjusted automatically based on any of the three
29temperature sensors. Each PWM output is individually adjustable and
30programmable. Once configured, the ADT7462 will adjust the PWM outputs in
31response to the measured temperatures without further host intervention.  This
32feature can also be disabled for manual control of the PWM's.
33
34Each of the measured inputs (voltage, temperature, fan speed) has
35corresponding high/low limit values. The ADT7462 will signal an ALARM if
36any measured value exceeds either limit.
37
38The ADT7462 samples all inputs continuously. The driver will not read
39the registers more often than once every other second. Further,
40configuration data is only read once per minute.
41
42Special Features
43----------------
44
45The ADT7462 have a 10-bit ADC and can therefore measure temperatures
46with 0.25 degC resolution.
47
48The Analog Devices datasheet is very detailed and describes a procedure for
49determining an optimal configuration for the automatic PWM control.
50
51The driver will report sensor labels when it is able to determine that
52information from the configuration registers.
53
54Configuration Notes
55-------------------
56
57Besides standard interfaces driver adds the following:
58
59* PWM Control
60
61* pwm#_auto_point1_pwm and temp#_auto_point1_temp and
62* pwm#_auto_point2_pwm and temp#_auto_point2_temp -
63
64  - point1: Set the pwm speed at a lower temperature bound.
65  - point2: Set the pwm speed at a higher temperature bound.
66
67The ADT7462 will scale the pwm between the lower and higher pwm speed when
68the temperature is between the two temperature boundaries.  PWM values range
69from 0 (off) to 255 (full speed).  Fan speed will be set to maximum when the
70temperature sensor associated with the PWM control exceeds temp#_max.
71