diff options
author | Ralf Baechle <ralf@linux-mips.org> | 2013-02-21 10:16:55 -0500 |
---|---|---|
committer | Ralf Baechle <ralf@linux-mips.org> | 2013-02-22 04:07:30 -0500 |
commit | edb15d83a875a1f4b1576188844db5c330c3267d (patch) | |
tree | 74d54eab401b6ccf2a6ad4821227108a8d160f03 /Documentation/hwmon/lm73 | |
parent | 8bfc245f9ad7bd4e461179e4e7852ef99b8b6144 (diff) | |
parent | a0b1c42951dd06ec83cc1bc2c9788131d9fefcd8 (diff) |
Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux into mips-for-linux-next
Conflicts:
include/linux/ssb/ssb_driver_gige.h
Also resolves a logical merge conflict in drivers/net/ethernet/broadcom/-
bgmac.c due to change of an API.
Diffstat (limited to 'Documentation/hwmon/lm73')
-rw-r--r-- | Documentation/hwmon/lm73 | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/Documentation/hwmon/lm73 b/Documentation/hwmon/lm73 new file mode 100644 index 000000000000..8af059dcb642 --- /dev/null +++ b/Documentation/hwmon/lm73 | |||
@@ -0,0 +1,90 @@ | |||
1 | Kernel driver lm73 | ||
2 | ================== | ||
3 | |||
4 | Supported chips: | ||
5 | * Texas Instruments LM73 | ||
6 | Prefix: 'lm73' | ||
7 | Addresses scanned: I2C 0x48, 0x49, 0x4a, 0x4c, 0x4d, and 0x4e | ||
8 | Datasheet: Publicly available at the Texas Instruments website | ||
9 | http://www.ti.com/product/lm73 | ||
10 | |||
11 | Author: Guillaume Ligneul <guillaume.ligneul@gmail.com> | ||
12 | Documentation: Chris Verges <kg4ysn@gmail.com> | ||
13 | |||
14 | |||
15 | Description | ||
16 | ----------- | ||
17 | |||
18 | The LM73 is a digital temperature sensor. All temperature values are | ||
19 | given in degrees Celsius. | ||
20 | |||
21 | Measurement Resolution Support | ||
22 | ------------------------------ | ||
23 | |||
24 | The LM73 supports four resolutions, defined in terms of degrees C per | ||
25 | LSB: 0.25, 0.125, 0.0625, and 0.3125. Changing the resolution mode | ||
26 | affects the conversion time of the LM73's analog-to-digital converter. | ||
27 | From userspace, the desired resolution can be specified as a function of | ||
28 | conversion time via the 'update_interval' sysfs attribute for the | ||
29 | device. This attribute will normalize ranges of input values to the | ||
30 | maximum times defined for the resolution in the datasheet. | ||
31 | |||
32 | Resolution Conv. Time Input Range | ||
33 | (C/LSB) (msec) (msec) | ||
34 | -------------------------------------- | ||
35 | 0.25 14 0..14 | ||
36 | 0.125 28 15..28 | ||
37 | 0.0625 56 29..56 | ||
38 | 0.03125 112 57..infinity | ||
39 | -------------------------------------- | ||
40 | |||
41 | The following examples show how the 'update_interval' attribute can be | ||
42 | used to change the conversion time: | ||
43 | |||
44 | $ echo 0 > update_interval | ||
45 | $ cat update_interval | ||
46 | 14 | ||
47 | $ cat temp1_input | ||
48 | 24250 | ||
49 | |||
50 | $ echo 22 > update_interval | ||
51 | $ cat update_interval | ||
52 | 28 | ||
53 | $ cat temp1_input | ||
54 | 24125 | ||
55 | |||
56 | $ echo 56 > update_interval | ||
57 | $ cat update_interval | ||
58 | 56 | ||
59 | $ cat temp1_input | ||
60 | 24062 | ||
61 | |||
62 | $ echo 85 > update_interval | ||
63 | $ cat update_interval | ||
64 | 112 | ||
65 | $ cat temp1_input | ||
66 | 24031 | ||
67 | |||
68 | As shown here, the lm73 driver automatically adjusts any user input for | ||
69 | 'update_interval' via a step function. Reading back the | ||
70 | 'update_interval' value after a write operation will confirm the | ||
71 | conversion time actively in use. | ||
72 | |||
73 | Mathematically, the resolution can be derived from the conversion time | ||
74 | via the following function: | ||
75 | |||
76 | g(x) = 0.250 * [log(x/14) / log(2)] | ||
77 | |||
78 | where 'x' is the output from 'update_interval' and 'g(x)' is the | ||
79 | resolution in degrees C per LSB. | ||
80 | |||
81 | Alarm Support | ||
82 | ------------- | ||
83 | |||
84 | The LM73 features a simple over-temperature alarm mechanism. This | ||
85 | feature is exposed via the sysfs attributes. | ||
86 | |||
87 | The attributes 'temp1_max_alarm' and 'temp1_min_alarm' are flags | ||
88 | provided by the LM73 that indicate whether the measured temperature has | ||
89 | passed the 'temp1_max' and 'temp1_min' thresholds, respectively. These | ||
90 | values _must_ be read to clear the registers on the LM73. | ||