Root/
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 |
11 | Prefix: 'lm89' (no auto-detection) |
12 | Addresses scanned: I2C 0x4c and 0x4d |
13 | Datasheet: Publicly available at the National Semiconductor website |
14 | http://www.national.com/mpf/LM/LM89.html |
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 |
24 | http://www.national.com/mpf/LM/LM86.html |
25 | * Analog Devices ADM1032 |
26 | Prefix: 'adm1032' |
27 | Addresses scanned: I2C 0x4c and 0x4d |
28 | Datasheet: Publicly available at the ON Semiconductor website |
29 | http://www.onsemi.com/PowerSolutions/product.do?id=ADM1032 |
30 | * Analog Devices ADT7461 |
31 | Prefix: 'adt7461' |
32 | Addresses scanned: I2C 0x4c and 0x4d |
33 | Datasheet: Publicly available at the ON Semiconductor website |
34 | http://www.onsemi.com/PowerSolutions/product.do?id=ADT7461 |
35 | * Analog Devices ADT7461A |
36 | Prefix: 'adt7461a' |
37 | Addresses scanned: I2C 0x4c and 0x4d |
38 | Datasheet: Publicly available at the ON Semiconductor website |
39 | http://www.onsemi.com/PowerSolutions/product.do?id=ADT7461A |
40 | * ON Semiconductor NCT1008 |
41 | Prefix: 'nct1008' |
42 | Addresses scanned: I2C 0x4c and 0x4d |
43 | Datasheet: Publicly available at the ON Semiconductor website |
44 | http://www.onsemi.com/PowerSolutions/product.do?id=NCT1008 |
45 | * Maxim MAX6646 |
46 | Prefix: 'max6646' |
47 | Addresses scanned: I2C 0x4d |
48 | Datasheet: Publicly available at the Maxim website |
49 | http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497 |
50 | * Maxim MAX6647 |
51 | Prefix: 'max6646' |
52 | Addresses scanned: I2C 0x4e |
53 | Datasheet: Publicly available at the Maxim website |
54 | http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497 |
55 | * Maxim MAX6648 |
56 | Prefix: 'max6646' |
57 | Addresses scanned: I2C 0x4c |
58 | Datasheet: Publicly available at the Maxim website |
59 | http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3500 |
60 | * Maxim MAX6649 |
61 | Prefix: 'max6646' |
62 | Addresses scanned: I2C 0x4c |
63 | Datasheet: Publicly available at the Maxim website |
64 | http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497 |
65 | * Maxim MAX6657 |
66 | Prefix: 'max6657' |
67 | Addresses scanned: I2C 0x4c |
68 | Datasheet: Publicly available at the Maxim website |
69 | http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578 |
70 | * Maxim MAX6658 |
71 | Prefix: 'max6657' |
72 | Addresses scanned: I2C 0x4c |
73 | Datasheet: Publicly available at the Maxim website |
74 | http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578 |
75 | * Maxim MAX6659 |
76 | Prefix: 'max6659' |
77 | Addresses scanned: I2C 0x4c, 0x4d, 0x4e |
78 | Datasheet: Publicly available at the Maxim website |
79 | http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578 |
80 | * Maxim MAX6680 |
81 | Prefix: 'max6680' |
82 | Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b, |
83 | 0x4c, 0x4d and 0x4e |
84 | Datasheet: Publicly available at the Maxim website |
85 | http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3370 |
86 | * Maxim MAX6681 |
87 | Prefix: 'max6680' |
88 | Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b, |
89 | 0x4c, 0x4d and 0x4e |
90 | Datasheet: Publicly available at the Maxim website |
91 | http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3370 |
92 | * Maxim MAX6692 |
93 | Prefix: 'max6646' |
94 | Addresses scanned: I2C 0x4c |
95 | Datasheet: Publicly available at the Maxim website |
96 | http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3500 |
97 | * Maxim MAX6695 |
98 | Prefix: 'max6695' |
99 | Addresses scanned: I2C 0x18 |
100 | Datasheet: Publicly available at the Maxim website |
101 | http://www.maxim-ic.com/datasheet/index.mvp/id/4199 |
102 | * Maxim MAX6696 |
103 | Prefix: 'max6695' |
104 | Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b, |
105 | 0x4c, 0x4d and 0x4e |
106 | Datasheet: Publicly available at the Maxim website |
107 | http://www.maxim-ic.com/datasheet/index.mvp/id/4199 |
108 | * Winbond/Nuvoton W83L771W/G |
109 | Prefix: 'w83l771' |
110 | Addresses scanned: I2C 0x4c |
111 | Datasheet: No longer available |
112 | * Winbond/Nuvoton W83L771AWG/ASG |
113 | Prefix: 'w83l771' |
114 | Addresses scanned: I2C 0x4c |
115 | Datasheet: Not publicly available, can be requested from Nuvoton |
116 | * Philips/NXP SA56004X |
117 | Prefix: 'sa56004' |
118 | Addresses scanned: I2C 0x48 through 0x4F |
119 | Datasheet: Publicly available at NXP website |
120 | http://ics.nxp.com/products/interface/datasheet/sa56004x.pdf |
121 | |
122 | Author: Jean Delvare <khali@linux-fr.org> |
123 | |
124 | |
125 | Description |
126 | ----------- |
127 | |
128 | The LM90 is a digital temperature sensor. It senses its own temperature as |
129 | well as the temperature of up to one external diode. It is compatible |
130 | with many other devices, many of which are supported by this driver. |
131 | |
132 | Note that there is no easy way to differentiate between the MAX6657, |
133 | MAX6658 and MAX6659 variants. The extra features of the MAX6659 are only |
134 | supported by this driver if the chip is located at address 0x4d or 0x4e, |
135 | or if the chip type is explicitly selected as max6659. |
136 | The MAX6680 and MAX6681 only differ in their pinout, therefore they obviously |
137 | can't (and don't need to) be distinguished. |
138 | |
139 | The specificity of this family of chipsets over the ADM1021/LM84 |
140 | family is that it features critical limits with hysteresis, and an |
141 | increased resolution of the remote temperature measurement. |
142 | |
143 | The different chipsets of the family are not strictly identical, although |
144 | very similar. For reference, here comes a non-exhaustive list of specific |
145 | features: |
146 | |
147 | LM90: |
148 | * Filter and alert configuration register at 0xBF. |
149 | * ALERT is triggered by temperatures over critical limits. |
150 | |
151 | LM86 and LM89: |
152 | * Same as LM90 |
153 | * Better external channel accuracy |
154 | |
155 | LM99: |
156 | * Same as LM89 |
157 | * External temperature shifted by 16 degrees down |
158 | |
159 | ADM1032: |
160 | * Consecutive alert register at 0x22. |
161 | * Conversion averaging. |
162 | * Up to 64 conversions/s. |
163 | * ALERT is triggered by open remote sensor. |
164 | * SMBus PEC support for Write Byte and Receive Byte transactions. |
165 | |
166 | ADT7461, ADT7461A, NCT1008: |
167 | * Extended temperature range (breaks compatibility) |
168 | * Lower resolution for remote temperature |
169 | |
170 | MAX6657 and MAX6658: |
171 | * Better local resolution |
172 | * Remote sensor type selection |
173 | |
174 | MAX6659: |
175 | * Better local resolution |
176 | * Selectable address |
177 | * Second critical temperature limit |
178 | * Remote sensor type selection |
179 | |
180 | MAX6680 and MAX6681: |
181 | * Selectable address |
182 | * Remote sensor type selection |
183 | |
184 | MAX6695 and MAX6696: |
185 | * Better local resolution |
186 | * Selectable address (max6696) |
187 | * Second critical temperature limit |
188 | * Two remote sensors |
189 | |
190 | W83L771W/G |
191 | * The G variant is lead-free, otherwise similar to the W. |
192 | * Filter and alert configuration register at 0xBF |
193 | * Moving average (depending on conversion rate) |
194 | |
195 | W83L771AWG/ASG |
196 | * Successor of the W83L771W/G, same features. |
197 | * The AWG and ASG variants only differ in package format. |
198 | * Diode ideality factor configuration (remote sensor) at 0xE3 |
199 | |
200 | SA56004X: |
201 | * Better local resolution |
202 | |
203 | All temperature values are given in degrees Celsius. Resolution |
204 | is 1.0 degree for the local temperature, 0.125 degree for the remote |
205 | temperature, except for the MAX6657, MAX6658 and MAX6659 which have a |
206 | resolution of 0.125 degree for both temperatures. |
207 | |
208 | Each sensor has its own high and low limits, plus a critical limit. |
209 | Additionally, there is a relative hysteresis value common to both critical |
210 | values. To make life easier to user-space applications, two absolute values |
211 | are exported, one for each channel, but these values are of course linked. |
212 | Only the local hysteresis can be set from user-space, and the same delta |
213 | applies to the remote hysteresis. |
214 | |
215 | The lm90 driver will not update its values more frequently than configured with |
216 | the update_interval attribute; reading them more often will do no harm, but will |
217 | return 'old' values. |
218 | |
219 | SMBus Alert Support |
220 | ------------------- |
221 | |
222 | This driver has basic support for SMBus alert. When an alert is received, |
223 | the status register is read and the faulty temperature channel is logged. |
224 | |
225 | The Analog Devices chips (ADM1032, ADT7461 and ADT7461A) and ON |
226 | Semiconductor chips (NCT1008) do not implement the SMBus alert protocol |
227 | properly so additional care is needed: the ALERT output is disabled when |
228 | an alert is received, and is re-enabled only when the alarm is gone. |
229 | Otherwise the chip would block alerts from other chips in the bus as long |
230 | as the alarm is active. |
231 | |
232 | PEC Support |
233 | ----------- |
234 | |
235 | The ADM1032 is the only chip of the family which supports PEC. It does |
236 | not support PEC on all transactions though, so some care must be taken. |
237 | |
238 | When reading a register value, the PEC byte is computed and sent by the |
239 | ADM1032 chip. However, in the case of a combined transaction (SMBus Read |
240 | Byte), the ADM1032 computes the CRC value over only the second half of |
241 | the message rather than its entirety, because it thinks the first half |
242 | of the message belongs to a different transaction. As a result, the CRC |
243 | value differs from what the SMBus master expects, and all reads fail. |
244 | |
245 | For this reason, the lm90 driver will enable PEC for the ADM1032 only if |
246 | the bus supports the SMBus Send Byte and Receive Byte transaction types. |
247 | These transactions will be used to read register values, instead of |
248 | SMBus Read Byte, and PEC will work properly. |
249 | |
250 | Additionally, the ADM1032 doesn't support SMBus Send Byte with PEC. |
251 | Instead, it will try to write the PEC value to the register (because the |
252 | SMBus Send Byte transaction with PEC is similar to a Write Byte transaction |
253 | without PEC), which is not what we want. Thus, PEC is explicitly disabled |
254 | on SMBus Send Byte transactions in the lm90 driver. |
255 | |
256 | PEC on byte data transactions represents a significant increase in bandwidth |
257 | usage (+33% for writes, +25% for reads) in normal conditions. With the need |
258 | to use two SMBus transaction for reads, this overhead jumps to +50%. Worse, |
259 | two transactions will typically mean twice as much delay waiting for |
260 | transaction completion, effectively doubling the register cache refresh time. |
261 | I guess reliability comes at a price, but it's quite expensive this time. |
262 | |
263 | So, as not everyone might enjoy the slowdown, PEC can be disabled through |
264 | sysfs. Just write 0 to the "pec" file and PEC will be disabled. Write 1 |
265 | to that file to enable PEC again. |
266 |
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