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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
Guenter Roeck13c84952010-10-28 20:31:43 +020066 Prefix: 'max6659'
67 Addresses scanned: I2C 0x4c, 0x4d, 0x4e
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +000068 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
Guenter Roeck06e1c0a2010-10-28 20:31:43 +020087 * Maxim MAX6695
88 Prefix: 'max6695'
89 Addresses scanned: I2C 0x18
90 Datasheet: Publicly available at the Maxim website
91 http://www.maxim-ic.com/datasheet/index.mvp/id/4199
92 * Maxim MAX6696
93 Prefix: 'max6695'
94 Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
95 0x4c, 0x4d and 0x4e
96 Datasheet: Publicly available at the Maxim website
97 http://www.maxim-ic.com/datasheet/index.mvp/id/4199
Jean Delvare6771ea12010-03-05 22:17:13 +010098 * Winbond/Nuvoton W83L771AWG/ASG
99 Prefix: 'w83l771'
100 Addresses scanned: I2C 0x4c
101 Datasheet: Not publicly available, can be requested from Nuvoton
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000102
103
104Author: Jean Delvare <khali@linux-fr.org>
105
106
107Description
108-----------
109
110The LM90 is a digital temperature sensor. It senses its own temperature as
111well as the temperature of up to one external diode. It is compatible
Nate Case23b2d472008-10-17 17:51:10 +0200112with many other devices, many of which are supported by this driver.
Rainer Birkenmaier32c82a92007-06-09 10:11:16 -0400113
114Note that there is no easy way to differentiate between the MAX6657,
Guenter Roeck69487082010-10-28 20:31:43 +0200115MAX6658 and MAX6659 variants. The extra features of the MAX6659 are only
116supported by this driver if the chip is located at address 0x4d or 0x4e,
117or if the chip type is explicitly selected as max6659.
118The MAX6680 and MAX6681 only differ in their pinout, therefore they obviously
119can't (and don't need to) be distinguished.
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000120
121The specificity of this family of chipsets over the ADM1021/LM84
122family is that it features critical limits with hysteresis, and an
123increased resolution of the remote temperature measurement.
124
125The different chipsets of the family are not strictly identical, although
Jean Delvaref65e1702008-10-17 17:51:09 +0200126very similar. For reference, here comes a non-exhaustive list of specific
127features:
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000128
129LM90:
130 * Filter and alert configuration register at 0xBF.
131 * ALERT is triggered by temperatures over critical limits.
132
133LM86 and LM89:
134 * Same as LM90
135 * Better external channel accuracy
136
137LM99:
138 * Same as LM89
139 * External temperature shifted by 16 degrees down
140
141ADM1032:
142 * Consecutive alert register at 0x22.
143 * Conversion averaging.
144 * Up to 64 conversions/s.
145 * ALERT is triggered by open remote sensor.
Jean Delvarec3df5802005-10-26 21:39:40 +0200146 * SMBus PEC support for Write Byte and Receive Byte transactions.
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000147
Rainer Birkenmaier32c82a92007-06-09 10:11:16 -0400148ADT7461:
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000149 * Extended temperature range (breaks compatibility)
150 * Lower resolution for remote temperature
151
152MAX6657 and MAX6658:
Jean Delvaref65e1702008-10-17 17:51:09 +0200153 * Better local resolution
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000154 * Remote sensor type selection
155
Rainer Birkenmaier32c82a92007-06-09 10:11:16 -0400156MAX6659:
Jean Delvaref65e1702008-10-17 17:51:09 +0200157 * Better local resolution
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000158 * Selectable address
159 * Second critical temperature limit
160 * Remote sensor type selection
161
Rainer Birkenmaier32c82a92007-06-09 10:11:16 -0400162MAX6680 and MAX6681:
163 * Selectable address
164 * Remote sensor type selection
165
Guenter Roeck06e1c0a2010-10-28 20:31:43 +0200166MAX6695 and MAX6696:
167 * Better local resolution
168 * Selectable address (max6696)
169 * Second critical temperature limit
170 * Two remote sensors
171
Jean Delvare6771ea12010-03-05 22:17:13 +0100172W83L771AWG/ASG
173 * The AWG and ASG variants only differ in package format.
174 * Filter and alert configuration register at 0xBF
175 * Diode ideality factor configuration (remote sensor) at 0xE3
176 * Moving average (depending on conversion rate)
177
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000178All temperature values are given in degrees Celsius. Resolution
179is 1.0 degree for the local temperature, 0.125 degree for the remote
Jean Delvaref65e1702008-10-17 17:51:09 +0200180temperature, except for the MAX6657, MAX6658 and MAX6659 which have a
181resolution of 0.125 degree for both temperatures.
R.Marek@sh.cvut.cz7f15b662005-05-26 12:42:19 +0000182
183Each sensor has its own high and low limits, plus a critical limit.
184Additionally, there is a relative hysteresis value common to both critical
185values. To make life easier to user-space applications, two absolute values
186are exported, one for each channel, but these values are of course linked.
187Only the local hysteresis can be set from user-space, and the same delta
188applies to the remote hysteresis.
189
190The lm90 driver will not update its values more frequently than every
191other second; reading them more often will do no harm, but will return
192'old' values.
193
Jean Delvare53de3342010-03-05 22:17:15 +0100194SMBus Alert Support
195-------------------
196
197This driver has basic support for SMBus alert. When an alert is received,
198the status register is read and the faulty temperature channel is logged.
199
200The Analog Devices chips (ADM1032 and ADT7461) do not implement the SMBus
201alert protocol properly so additional care is needed: the ALERT output is
202disabled when an alert is received, and is re-enabled only when the alarm
203is gone. Otherwise the chip would block alerts from other chips in the bus
204as long as the alarm is active.
205
Jean Delvarec3df5802005-10-26 21:39:40 +0200206PEC Support
207-----------
208
209The ADM1032 is the only chip of the family which supports PEC. It does
210not support PEC on all transactions though, so some care must be taken.
211
212When reading a register value, the PEC byte is computed and sent by the
213ADM1032 chip. However, in the case of a combined transaction (SMBus Read
214Byte), the ADM1032 computes the CRC value over only the second half of
215the message rather than its entirety, because it thinks the first half
216of the message belongs to a different transaction. As a result, the CRC
217value differs from what the SMBus master expects, and all reads fail.
218
219For this reason, the lm90 driver will enable PEC for the ADM1032 only if
220the bus supports the SMBus Send Byte and Receive Byte transaction types.
221These transactions will be used to read register values, instead of
222SMBus Read Byte, and PEC will work properly.
223
224Additionally, the ADM1032 doesn't support SMBus Send Byte with PEC.
225Instead, it will try to write the PEC value to the register (because the
226SMBus Send Byte transaction with PEC is similar to a Write Byte transaction
Jean Delvare09664152007-06-09 10:11:15 -0400227without PEC), which is not what we want. Thus, PEC is explicitly disabled
Jean Delvarec3df5802005-10-26 21:39:40 +0200228on SMBus Send Byte transactions in the lm90 driver.
229
230PEC on byte data transactions represents a significant increase in bandwidth
231usage (+33% for writes, +25% for reads) in normal conditions. With the need
232to use two SMBus transaction for reads, this overhead jumps to +50%. Worse,
233two transactions will typically mean twice as much delay waiting for
234transaction completion, effectively doubling the register cache refresh time.
235I guess reliability comes at a price, but it's quite expensive this time.
236
237So, as not everyone might enjoy the slowdown, PEC can be disabled through
238sysfs. Just write 0 to the "pec" file and PEC will be disabled. Write 1
239to that file to enable PEC again.