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