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R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +00001Kernel driver lm90
2==================
3
4Supported chips:
5 * National Semiconductor LM90
6 Prefix: 'lm90'
7 Addresses scanned: I2C 0x4c
8 Datasheet: Publicly available at the National Semiconductor website
9 http://www.national.com/pf/LM/LM90.html
10 * National Semiconductor LM89
Jean Delvare97ae60b2008-10-26 17:04:39 +010011 Prefix: 'lm89' (no auto-detection)
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +000012 Addresses scanned: I2C 0x4c and 0x4d
13 Datasheet: Publicly available at the National Semiconductor website
Jean Delvarea874a102008-10-17 17:51:10 +020014 http://www.national.com/mpf/LM/LM89.html
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +000015 * National Semiconductor LM99
16 Prefix: 'lm99'
17 Addresses scanned: I2C 0x4c and 0x4d
18 Datasheet: Publicly available at the National Semiconductor website
19 http://www.national.com/pf/LM/LM99.html
20 * National Semiconductor LM86
21 Prefix: 'lm86'
22 Addresses scanned: I2C 0x4c
23 Datasheet: Publicly available at the National Semiconductor website
Jean Delvarea874a102008-10-17 17:51:10 +020024 http://www.national.com/mpf/LM/LM86.html
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +000025 * Analog Devices ADM1032
26 Prefix: 'adm1032'
Jean Delvare90209b42005-10-26 22:20:21 +020027 Addresses scanned: I2C 0x4c and 0x4d
Jean Delvarea874a102008-10-17 17:51:10 +020028 Datasheet: Publicly available at the ON Semiconductor website
29 http://www.onsemi.com/PowerSolutions/product.do?id=ADM1032
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +000030 * Analog Devices ADT7461
31 Prefix: 'adt7461'
Jean Delvare90209b42005-10-26 22:20:21 +020032 Addresses scanned: I2C 0x4c and 0x4d
Jean Delvarea874a102008-10-17 17:51:10 +020033 Datasheet: Publicly available at the ON Semiconductor website
34 http://www.onsemi.com/PowerSolutions/product.do?id=ADT7461
Ben Hutchings271dabf2008-10-17 17:51:11 +020035 * Maxim MAX6646
36 Prefix: 'max6646'
37 Addresses scanned: I2C 0x4d
38 Datasheet: Publicly available at the Maxim website
39 http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
40 * Maxim MAX6647
41 Prefix: 'max6646'
42 Addresses scanned: I2C 0x4e
43 Datasheet: Publicly available at the Maxim website
44 http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
Darrick J. Wong1a51e062009-03-12 13:36:38 +010045 * Maxim MAX6648
46 Prefix: 'max6646'
47 Addresses scanned: I2C 0x4c
48 Datasheet: Publicly available at the Maxim website
49 http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3500
Ben Hutchings271dabf2008-10-17 17:51:11 +020050 * Maxim MAX6649
51 Prefix: 'max6646'
52 Addresses scanned: I2C 0x4c
53 Datasheet: Publicly available at the Maxim website
54 http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +000055 * Maxim MAX6657
56 Prefix: 'max6657'
57 Addresses scanned: I2C 0x4c
58 Datasheet: Publicly available at the Maxim website
59 http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578
60 * Maxim MAX6658
61 Prefix: 'max6657'
62 Addresses scanned: I2C 0x4c
63 Datasheet: Publicly available at the Maxim website
64 http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578
65 * Maxim MAX6659
66 Prefix: 'max6657'
67 Addresses scanned: I2C 0x4c, 0x4d (unsupported 0x4e)
68 Datasheet: Publicly available at the Maxim website
69 http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578
Rainer Birkenmaier32c82a92007-06-09 10:11:16 -040070 * Maxim MAX6680
71 Prefix: 'max6680'
72 Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
73 0x4c, 0x4d and 0x4e
74 Datasheet: Publicly available at the Maxim website
75 http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3370
76 * Maxim MAX6681
77 Prefix: 'max6680'
78 Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
79 0x4c, 0x4d and 0x4e
80 Datasheet: Publicly available at the Maxim website
81 http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3370
Darrick J. Wong1a51e062009-03-12 13:36:38 +010082 * Maxim MAX6692
83 Prefix: 'max6646'
84 Addresses scanned: I2C 0x4c
85 Datasheet: Publicly available at the Maxim website
86 http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3500
Jean Delvare6771ea12010-03-05 22:17:13 +010087 * Winbond/Nuvoton W83L771AWG/ASG
88 Prefix: 'w83l771'
89 Addresses scanned: I2C 0x4c
90 Datasheet: Not publicly available, can be requested from Nuvoton
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +000091
92
93Author: Jean Delvare <khali@linux-fr.org>
94
95
96Description
97-----------
98
99The LM90 is a digital temperature sensor. It senses its own temperature as
100well as the temperature of up to one external diode. It is compatible
Nate Case23b2d472008-10-17 17:51:10 +0200101with many other devices, many of which are supported by this driver.
Rainer Birkenmaier32c82a92007-06-09 10:11:16 -0400102
103Note that there is no easy way to differentiate between the MAX6657,
104MAX6658 and MAX6659 variants. The extra address and features of the
105MAX6659 are not supported by this driver. The MAX6680 and MAX6681 only
106differ in their pinout, therefore they obviously can't (and don't need to)
Nate Case23b2d472008-10-17 17:51:10 +0200107be distinguished.
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000108
109The specificity of this family of chipsets over the ADM1021/LM84
110family is that it features critical limits with hysteresis, and an
111increased resolution of the remote temperature measurement.
112
113The different chipsets of the family are not strictly identical, although
Jean Delvaref65e1702008-10-17 17:51:09 +0200114very similar. For reference, here comes a non-exhaustive list of specific
115features:
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000116
117LM90:
118 * Filter and alert configuration register at 0xBF.
119 * ALERT is triggered by temperatures over critical limits.
120
121LM86 and LM89:
122 * Same as LM90
123 * Better external channel accuracy
124
125LM99:
126 * Same as LM89
127 * External temperature shifted by 16 degrees down
128
129ADM1032:
130 * Consecutive alert register at 0x22.
131 * Conversion averaging.
132 * Up to 64 conversions/s.
133 * ALERT is triggered by open remote sensor.
Jean Delvarec3df5802005-10-26 21:39:40 +0200134 * SMBus PEC support for Write Byte and Receive Byte transactions.
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000135
Rainer Birkenmaier32c82a92007-06-09 10:11:16 -0400136ADT7461:
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000137 * Extended temperature range (breaks compatibility)
138 * Lower resolution for remote temperature
139
140MAX6657 and MAX6658:
Jean Delvaref65e1702008-10-17 17:51:09 +0200141 * Better local resolution
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000142 * Remote sensor type selection
143
Rainer Birkenmaier32c82a92007-06-09 10:11:16 -0400144MAX6659:
Jean Delvaref65e1702008-10-17 17:51:09 +0200145 * Better local resolution
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000146 * Selectable address
147 * Second critical temperature limit
148 * Remote sensor type selection
149
Rainer Birkenmaier32c82a92007-06-09 10:11:16 -0400150MAX6680 and MAX6681:
151 * Selectable address
152 * Remote sensor type selection
153
Jean Delvare6771ea12010-03-05 22:17:13 +0100154W83L771AWG/ASG
155 * The AWG and ASG variants only differ in package format.
156 * Filter and alert configuration register at 0xBF
157 * Diode ideality factor configuration (remote sensor) at 0xE3
158 * Moving average (depending on conversion rate)
159
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000160All temperature values are given in degrees Celsius. Resolution
161is 1.0 degree for the local temperature, 0.125 degree for the remote
Jean Delvaref65e1702008-10-17 17:51:09 +0200162temperature, except for the MAX6657, MAX6658 and MAX6659 which have a
163resolution of 0.125 degree for both temperatures.
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000164
165Each sensor has its own high and low limits, plus a critical limit.
166Additionally, there is a relative hysteresis value common to both critical
167values. To make life easier to user-space applications, two absolute values
168are exported, one for each channel, but these values are of course linked.
169Only the local hysteresis can be set from user-space, and the same delta
170applies to the remote hysteresis.
171
172The lm90 driver will not update its values more frequently than every
173other second; reading them more often will do no harm, but will return
174'old' values.
175
Jean Delvare53de3342010-03-05 22:17:15 +0100176SMBus Alert Support
177-------------------
178
179This driver has basic support for SMBus alert. When an alert is received,
180the status register is read and the faulty temperature channel is logged.
181
182The Analog Devices chips (ADM1032 and ADT7461) do not implement the SMBus
183alert protocol properly so additional care is needed: the ALERT output is
184disabled when an alert is received, and is re-enabled only when the alarm
185is gone. Otherwise the chip would block alerts from other chips in the bus
186as long as the alarm is active.
187
Jean Delvarec3df5802005-10-26 21:39:40 +0200188PEC Support
189-----------
190
191The ADM1032 is the only chip of the family which supports PEC. It does
192not support PEC on all transactions though, so some care must be taken.
193
194When reading a register value, the PEC byte is computed and sent by the
195ADM1032 chip. However, in the case of a combined transaction (SMBus Read
196Byte), the ADM1032 computes the CRC value over only the second half of
197the message rather than its entirety, because it thinks the first half
198of the message belongs to a different transaction. As a result, the CRC
199value differs from what the SMBus master expects, and all reads fail.
200
201For this reason, the lm90 driver will enable PEC for the ADM1032 only if
202the bus supports the SMBus Send Byte and Receive Byte transaction types.
203These transactions will be used to read register values, instead of
204SMBus Read Byte, and PEC will work properly.
205
206Additionally, the ADM1032 doesn't support SMBus Send Byte with PEC.
207Instead, it will try to write the PEC value to the register (because the
208SMBus Send Byte transaction with PEC is similar to a Write Byte transaction
Jean Delvare09664152007-06-09 10:11:15 -0400209without PEC), which is not what we want. Thus, PEC is explicitly disabled
Jean Delvarec3df5802005-10-26 21:39:40 +0200210on SMBus Send Byte transactions in the lm90 driver.
211
212PEC on byte data transactions represents a significant increase in bandwidth
213usage (+33% for writes, +25% for reads) in normal conditions. With the need
214to use two SMBus transaction for reads, this overhead jumps to +50%. Worse,
215two transactions will typically mean twice as much delay waiting for
216transaction completion, effectively doubling the register cache refresh time.
217I guess reliability comes at a price, but it's quite expensive this time.
218
219So, as not everyone might enjoy the slowdown, PEC can be disabled through
220sysfs. Just write 0 to the "pec" file and PEC will be disabled. Write 1
221to that file to enable PEC again.