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1 | Kernel driver adt7462 | ||
2 | ====================== | ||
3 | |||
4 | Supported chips: | ||
5 | * Analog Devices ADT7462 | ||
6 | Prefix: 'adt7462' | ||
7 | Addresses scanned: I2C 0x58, 0x5C | ||
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 ADT7462 chip family. | ||
16 | |||
17 | This chip is a bit of a beast. It has 8 counters for measuring fan speed. It | ||
18 | can also measure 13 voltages or 4 temperatures, or various combinations of the | ||
19 | two. See the chip documentation for more details about the exact set of | ||
20 | configurations. This driver does not allow one to configure the chip; that is | ||
21 | left to the system designer. | ||
22 | |||
23 | A sophisticated control system for the PWM outputs is designed into the ADT7462 | ||
24 | that allows fan speed to be adjusted automatically based on any of the three | ||
25 | temperature sensors. Each PWM output is individually adjustable and | ||
26 | programmable. Once configured, the ADT7462 will adjust the PWM outputs in | ||
27 | response to the measured temperatures without further host intervention. This | ||
28 | 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 ADT7462 will signal an ALARM if | ||
32 | any measured value exceeds either limit. | ||
33 | |||
34 | The ADT7462 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 ADT7462 have a 10-bit ADC and can therefore measure temperatures | ||
42 | with 0.25 degC resolution. | ||
43 | |||
44 | The Analog Devices datasheet is very detailed and describes a procedure for | ||
45 | determining an optimal configuration for the automatic PWM control. | ||
46 | |||
47 | The driver will report sensor labels when it is able to determine that | ||
48 | information from the configuration registers. | ||
49 | |||
50 | Configuration Notes | ||
51 | ------------------- | ||
52 | |||
53 | Besides 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 | |||
60 | point1: Set the pwm speed at a lower temperature bound. | ||
61 | point2: Set the pwm speed at a higher temperature bound. | ||
62 | |||
63 | The ADT7462 will scale the pwm between the lower and higher pwm speed when | ||
64 | the temperature is between the two temperature boundaries. PWM values range | ||
65 | from 0 (off) to 255 (full speed). Fan speed will be set to maximum when the | ||
66 | temperature sensor associated with the PWM control exceeds temp#_max. | ||
67 | |||