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authorGuenter Roeck <linux@roeck-us.net>2014-05-12 13:11:32 -0400
committerGuenter Roeck <linux@roeck-us.net>2014-05-21 19:02:23 -0400
commit57d60b1b7e0d0d32602587fd032d56d7ed9e1556 (patch)
tree832658f96f4dfbfadfe0aeefeacce67132f567b4 /Documentation/hwmon
parenta9622663e0406932612ffd44fde586e59df9de43 (diff)
hwmon: (emc1403) Add driver documentation
With the driver now supporting several chip variants, it is about time to document what is supported. Signed-off-by: Guenter Roeck <linux@roeck-us.net>
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1Kernel driver emc1403
2=====================
3
4Supported chips:
5 * SMSC / Microchip EMC1402, EMC1412
6 Addresses scanned: I2C 0x18, 0x1c, 0x29, 0x4c, 0x4d, 0x5c
7 Prefix: 'emc1402'
8 Datasheets:
9 http://ww1.microchip.com/downloads/en/DeviceDoc/1412.pdf
10 http://ww1.microchip.com/downloads/en/DeviceDoc/1402.pdf
11 * SMSC / Microchip EMC1403, EMC1404, EMC1413, EMC1414
12 Addresses scanned: I2C 0x18, 0x29, 0x4c, 0x4d
13 Prefix: 'emc1403', 'emc1404'
14 Datasheets:
15 http://ww1.microchip.com/downloads/en/DeviceDoc/1403_1404.pdf
16 http://ww1.microchip.com/downloads/en/DeviceDoc/1413_1414.pdf
17 * SMSC / Microchip EMC1422
18 Addresses scanned: I2C 0x4c
19 Prefix: 'emc1422'
20 Datasheet:
21 http://ww1.microchip.com/downloads/en/DeviceDoc/1422.pdf
22 * SMSC / Microchip EMC1423, EMC1424
23 Addresses scanned: I2C 0x4c
24 Prefix: 'emc1423', 'emc1424'
25 Datasheet:
26 http://ww1.microchip.com/downloads/en/DeviceDoc/1423_1424.pdf
27
28Author:
29 Kalhan Trisal <kalhan.trisal@intel.com
30
31
32Description
33-----------
34
35The Standard Microsystems Corporation (SMSC) / Microchip EMC14xx chips
36contain up to four temperature sensors. EMC14x2 support two sensors
37(one internal, one external). EMC14x3 support three sensors (one internal,
38two external), and EMC14x4 support four sensors (one internal, three
39external).
40
41The chips implement three limits for each sensor: low (tempX_min), high
42(tempX_max) and critical (tempX_crit.) The chips also implement an
43hysteresis mechanism which applies to all limits. The relative difference
44is stored in a single register on the chip, which means that the relative
45difference between the limit and its hysteresis is always the same for
46all three limits.
47
48This implementation detail implies the following:
49* When setting a limit, its hysteresis will automatically follow, the
50 difference staying unchanged. For example, if the old critical limit
51 was 80 degrees C, and the hysteresis was 75 degrees C, and you change
52 the critical limit to 90 degrees C, then the hysteresis will
53 automatically change to 85 degrees C.
54* While hysteresis limits can be set for all critical limits, setting a single
55 hysteresis value affects the hysteresis values for all limits on all sensors.
56* The limits should be set before the hysteresis.