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Commit | Line | Data |
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1 | Kernel driver lm90 |
2 | ================== | |
3 | ||
4 | Supported 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 | |
97ae60bb | 11 | Prefix: 'lm89' (no auto-detection) |
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12 | Addresses scanned: I2C 0x4c and 0x4d |
13 | Datasheet: Publicly available at the National Semiconductor website | |
a874a10c | 14 | http://www.national.com/mpf/LM/LM89.html |
7f15b664 RM |
15 | * 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 | |
a874a10c | 24 | http://www.national.com/mpf/LM/LM86.html |
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25 | * Analog Devices ADM1032 |
26 | Prefix: 'adm1032' | |
90209b42 | 27 | Addresses scanned: I2C 0x4c and 0x4d |
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28 | Datasheet: Publicly available at the ON Semiconductor website |
29 | http://www.onsemi.com/PowerSolutions/product.do?id=ADM1032 | |
7f15b664 RM |
30 | * Analog Devices ADT7461 |
31 | Prefix: 'adt7461' | |
90209b42 | 32 | Addresses scanned: I2C 0x4c and 0x4d |
a874a10c JD |
33 | Datasheet: Publicly available at the ON Semiconductor website |
34 | http://www.onsemi.com/PowerSolutions/product.do?id=ADT7461 | |
271dabf5 BH |
35 | * 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 | |
1a51e068 DW |
45 | * 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 | |
271dabf5 BH |
50 | * 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 | |
7f15b664 RM |
55 | * 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 | |
13c84951 GR |
66 | Prefix: 'max6659' |
67 | Addresses scanned: I2C 0x4c, 0x4d, 0x4e | |
7f15b664 RM |
68 | Datasheet: Publicly available at the Maxim website |
69 | http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578 | |
32c82a93 RB |
70 | * 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 | |
1a51e068 DW |
82 | * 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 | |
06e1c0a2 GR |
87 | * 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 | |
c4f99a2b JD |
98 | * Winbond/Nuvoton W83L771W/G |
99 | Prefix: 'w83l771' | |
100 | Addresses scanned: I2C 0x4c | |
101 | Datasheet: No longer available | |
6771ea1f JD |
102 | * Winbond/Nuvoton W83L771AWG/ASG |
103 | Prefix: 'w83l771' | |
104 | Addresses scanned: I2C 0x4c | |
105 | Datasheet: Not publicly available, can be requested from Nuvoton | |
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106 | |
107 | ||
108 | Author: Jean Delvare <khali@linux-fr.org> | |
109 | ||
110 | ||
111 | Description | |
112 | ----------- | |
113 | ||
114 | The LM90 is a digital temperature sensor. It senses its own temperature as | |
115 | well as the temperature of up to one external diode. It is compatible | |
23b2d477 | 116 | with many other devices, many of which are supported by this driver. |
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117 | |
118 | Note that there is no easy way to differentiate between the MAX6657, | |
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119 | MAX6658 and MAX6659 variants. The extra features of the MAX6659 are only |
120 | supported by this driver if the chip is located at address 0x4d or 0x4e, | |
121 | or if the chip type is explicitly selected as max6659. | |
122 | The MAX6680 and MAX6681 only differ in their pinout, therefore they obviously | |
123 | can't (and don't need to) be distinguished. | |
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124 | |
125 | The specificity of this family of chipsets over the ADM1021/LM84 | |
126 | family is that it features critical limits with hysteresis, and an | |
127 | increased resolution of the remote temperature measurement. | |
128 | ||
129 | The different chipsets of the family are not strictly identical, although | |
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130 | very similar. For reference, here comes a non-exhaustive list of specific |
131 | features: | |
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132 | |
133 | LM90: | |
134 | * Filter and alert configuration register at 0xBF. | |
135 | * ALERT is triggered by temperatures over critical limits. | |
136 | ||
137 | LM86 and LM89: | |
138 | * Same as LM90 | |
139 | * Better external channel accuracy | |
140 | ||
141 | LM99: | |
142 | * Same as LM89 | |
143 | * External temperature shifted by 16 degrees down | |
144 | ||
145 | ADM1032: | |
146 | * Consecutive alert register at 0x22. | |
147 | * Conversion averaging. | |
148 | * Up to 64 conversions/s. | |
149 | * ALERT is triggered by open remote sensor. | |
c3df5806 | 150 | * SMBus PEC support for Write Byte and Receive Byte transactions. |
7f15b664 | 151 | |
32c82a93 | 152 | ADT7461: |
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153 | * Extended temperature range (breaks compatibility) |
154 | * Lower resolution for remote temperature | |
155 | ||
156 | MAX6657 and MAX6658: | |
f65e1708 | 157 | * Better local resolution |
7f15b664 RM |
158 | * Remote sensor type selection |
159 | ||
32c82a93 | 160 | MAX6659: |
f65e1708 | 161 | * Better local resolution |
7f15b664 RM |
162 | * Selectable address |
163 | * Second critical temperature limit | |
164 | * Remote sensor type selection | |
165 | ||
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166 | MAX6680 and MAX6681: |
167 | * Selectable address | |
168 | * Remote sensor type selection | |
169 | ||
06e1c0a2 GR |
170 | MAX6695 and MAX6696: |
171 | * Better local resolution | |
172 | * Selectable address (max6696) | |
173 | * Second critical temperature limit | |
174 | * Two remote sensors | |
175 | ||
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176 | W83L771W/G |
177 | * The G variant is lead-free, otherwise similar to the W. | |
178 | * Filter and alert configuration register at 0xBF | |
179 | * Moving average (depending on conversion rate) | |
180 | ||
6771ea1f | 181 | W83L771AWG/ASG |
c4f99a2b | 182 | * Successor of the W83L771W/G, same features. |
6771ea1f | 183 | * The AWG and ASG variants only differ in package format. |
6771ea1f | 184 | * Diode ideality factor configuration (remote sensor) at 0xE3 |
6771ea1f | 185 | |
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186 | All temperature values are given in degrees Celsius. Resolution |
187 | is 1.0 degree for the local temperature, 0.125 degree for the remote | |
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188 | temperature, except for the MAX6657, MAX6658 and MAX6659 which have a |
189 | resolution of 0.125 degree for both temperatures. | |
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190 | |
191 | Each sensor has its own high and low limits, plus a critical limit. | |
192 | Additionally, there is a relative hysteresis value common to both critical | |
193 | values. To make life easier to user-space applications, two absolute values | |
194 | are exported, one for each channel, but these values are of course linked. | |
195 | Only the local hysteresis can be set from user-space, and the same delta | |
196 | applies to the remote hysteresis. | |
197 | ||
198 | The lm90 driver will not update its values more frequently than every | |
199 | other second; reading them more often will do no harm, but will return | |
200 | 'old' values. | |
201 | ||
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202 | SMBus Alert Support |
203 | ------------------- | |
204 | ||
205 | This driver has basic support for SMBus alert. When an alert is received, | |
206 | the status register is read and the faulty temperature channel is logged. | |
207 | ||
208 | The Analog Devices chips (ADM1032 and ADT7461) do not implement the SMBus | |
209 | alert protocol properly so additional care is needed: the ALERT output is | |
210 | disabled when an alert is received, and is re-enabled only when the alarm | |
211 | is gone. Otherwise the chip would block alerts from other chips in the bus | |
212 | as long as the alarm is active. | |
213 | ||
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214 | PEC Support |
215 | ----------- | |
216 | ||
217 | The ADM1032 is the only chip of the family which supports PEC. It does | |
218 | not support PEC on all transactions though, so some care must be taken. | |
219 | ||
220 | When reading a register value, the PEC byte is computed and sent by the | |
221 | ADM1032 chip. However, in the case of a combined transaction (SMBus Read | |
222 | Byte), the ADM1032 computes the CRC value over only the second half of | |
223 | the message rather than its entirety, because it thinks the first half | |
224 | of the message belongs to a different transaction. As a result, the CRC | |
225 | value differs from what the SMBus master expects, and all reads fail. | |
226 | ||
227 | For this reason, the lm90 driver will enable PEC for the ADM1032 only if | |
228 | the bus supports the SMBus Send Byte and Receive Byte transaction types. | |
229 | These transactions will be used to read register values, instead of | |
230 | SMBus Read Byte, and PEC will work properly. | |
231 | ||
232 | Additionally, the ADM1032 doesn't support SMBus Send Byte with PEC. | |
233 | Instead, it will try to write the PEC value to the register (because the | |
234 | SMBus Send Byte transaction with PEC is similar to a Write Byte transaction | |
0966415d | 235 | without PEC), which is not what we want. Thus, PEC is explicitly disabled |
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236 | on SMBus Send Byte transactions in the lm90 driver. |
237 | ||
238 | PEC on byte data transactions represents a significant increase in bandwidth | |
239 | usage (+33% for writes, +25% for reads) in normal conditions. With the need | |
240 | to use two SMBus transaction for reads, this overhead jumps to +50%. Worse, | |
241 | two transactions will typically mean twice as much delay waiting for | |
242 | transaction completion, effectively doubling the register cache refresh time. | |
243 | I guess reliability comes at a price, but it's quite expensive this time. | |
244 | ||
245 | So, as not everyone might enjoy the slowdown, PEC can be disabled through | |
246 | sysfs. Just write 0 to the "pec" file and PEC will be disabled. Write 1 | |
247 | to that file to enable PEC again. |