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f890c6a3 JD |
1 | Kernel driver adt7475 |
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 On Semiconductors website | |
9 | * Analog Devices ADT7475 | |
10 | Prefix: 'adt7475' | |
11 | Addresses scanned: I2C 0x2E | |
12 | Datasheet: Publicly available at the On Semiconductors website | |
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13 | * Analog Devices ADT7476 |
14 | Prefix: 'adt7476' | |
15 | Addresses scanned: I2C 0x2C, 0x2D, 0x2E | |
16 | Datasheet: Publicly available at the On Semiconductors website | |
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17 | * Analog Devices ADT7490 |
18 | Prefix: 'adt7490' | |
19 | Addresses scanned: I2C 0x2C, 0x2D, 0x2E | |
20 | Datasheet: Publicly available at the On Semiconductors website | |
f890c6a3 JD |
21 | |
22 | Authors: | |
23 | Jordan Crouse | |
24 | Hans de Goede | |
25 | Darrick J. Wong (documentation) | |
3d849981 | 26 | Jean Delvare |
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27 | |
28 | ||
29 | Description | |
30 | ----------- | |
31 | ||
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32 | This driver implements support for the Analog Devices ADT7473, ADT7475, |
33 | ADT7476 and ADT7490 chip family. The ADT7473 and ADT7475 differ only in | |
34 | minor details. The ADT7476 has additional features, including extra voltage | |
35 | measurement inputs and VID support. The ADT7490 also has additional | |
36 | features, including extra voltage measurement inputs and PECI support. All | |
37 | the supported chips will be collectively designed by the name "ADT747x" in | |
38 | the rest of this document. | |
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39 | |
40 | The ADT747x uses the 2-wire interface compatible with the SMBus 2.0 | |
41 | specification. Using an analog to digital converter it measures three (3) | |
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42 | temperatures and two (2) or more voltages. It has four (4) 16-bit counters |
43 | for measuring fan speed. There are three (3) PWM outputs that can be used | |
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44 | to control fan speed. |
45 | ||
46 | A sophisticated control system for the PWM outputs is designed into the | |
47 | ADT747x that allows fan speed to be adjusted automatically based on any of the | |
48 | three temperature sensors. Each PWM output is individually adjustable and | |
49 | programmable. Once configured, the ADT747x will adjust the PWM outputs in | |
50 | response to the measured temperatures without further host intervention. | |
51 | This feature can also be disabled for manual control of the PWM's. | |
52 | ||
53 | Each of the measured inputs (voltage, temperature, fan speed) has | |
54 | corresponding high/low limit values. The ADT747x will signal an ALARM if | |
55 | any measured value exceeds either limit. | |
56 | ||
57 | The ADT747x samples all inputs continuously. The driver will not read | |
58 | the registers more often than once every other second. Further, | |
59 | configuration data is only read once per minute. | |
60 | ||
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61 | Chip Differences Summary |
62 | ------------------------ | |
63 | ||
64 | ADT7473: | |
65 | * 2 voltage inputs | |
66 | * system acoustics optimizations (not implemented) | |
67 | ||
68 | ADT7475: | |
69 | * 2 voltage inputs | |
70 | ||
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71 | ADT7476: |
72 | * 5 voltage inputs | |
54fe4671 | 73 | * VID support |
d8d2ee07 | 74 | |
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75 | ADT7490: |
76 | * 6 voltage inputs | |
77 | * 1 Imon input (not implemented) | |
78 | * PECI support (not implemented) | |
79 | * 2 GPIO pins (not implemented) | |
80 | * system acoustics optimizations (not implemented) | |
81 | ||
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82 | Special Features |
83 | ---------------- | |
84 | ||
85 | The ADT747x has a 10-bit ADC and can therefore measure temperatures | |
86 | with a resolution of 0.25 degree Celsius. Temperature readings can be | |
87 | configured either for two's complement format or "Offset 64" format, | |
88 | wherein 64 is subtracted from the raw value to get the temperature value. | |
89 | ||
90 | The datasheet is very detailed and describes a procedure for determining | |
91 | an optimal configuration for the automatic PWM control. | |
92 | ||
93 | Fan Speed Control | |
94 | ----------------- | |
95 | ||
96 | The driver exposes two trip points per PWM channel. | |
97 | ||
98 | point1: Set the PWM speed at the lower temperature bound | |
99 | point2: Set the PWM speed at the higher temperature bound | |
100 | ||
101 | The ADT747x will scale the PWM linearly between the lower and higher PWM | |
102 | speed when the temperature is between the two temperature boundaries. | |
103 | Temperature boundaries are associated to temperature channels rather than | |
104 | PWM outputs, and a given PWM output can be controlled by several temperature | |
105 | channels. As a result, the ADT747x may compute more than one PWM value | |
106 | for a channel at a given time, in which case the maximum value (fastest | |
107 | fan speed) is applied. PWM values range from 0 (off) to 255 (full speed). | |
108 | ||
109 | Fan speed may be set to maximum when the temperature sensor associated with | |
110 | the PWM control exceeds temp#_max. | |
111 | ||
112 | Notes | |
113 | ----- | |
114 | ||
115 | The nVidia binary driver presents an ADT7473 chip via an on-card i2c bus. | |
116 | Unfortunately, they fail to set the i2c adapter class, so this driver may | |
117 | fail to find the chip until the nvidia driver is patched. |