1Kernel driver lm90
2==================
3
4Supported chips:
5
6  * National Semiconductor LM90
7
8    Prefix: 'lm90'
9
10    Addresses scanned: I2C 0x4c
11
12    Datasheet: Publicly available at the National Semiconductor website
13
14	       http://www.national.com/pf/LM/LM90.html
15
16  * National Semiconductor LM89
17
18    Prefix: 'lm89' (no auto-detection)
19
20    Addresses scanned: I2C 0x4c and 0x4d
21
22    Datasheet: Publicly available at the National Semiconductor website
23
24	       http://www.national.com/mpf/LM/LM89.html
25
26  * National Semiconductor LM99
27
28    Prefix: 'lm99'
29
30    Addresses scanned: I2C 0x4c and 0x4d
31
32    Datasheet: Publicly available at the National Semiconductor website
33
34	       http://www.national.com/pf/LM/LM99.html
35
36  * National Semiconductor LM86
37
38    Prefix: 'lm86'
39
40    Addresses scanned: I2C 0x4c
41
42    Datasheet: Publicly available at the National Semiconductor website
43
44	       http://www.national.com/mpf/LM/LM86.html
45
46  * Analog Devices ADM1032
47
48    Prefix: 'adm1032'
49
50    Addresses scanned: I2C 0x4c and 0x4d
51
52    Datasheet: Publicly available at the ON Semiconductor website
53
54	       https://www.onsemi.com/PowerSolutions/product.do?id=ADM1032
55
56  * Analog Devices ADT7461
57
58    Prefix: 'adt7461'
59
60    Addresses scanned: I2C 0x4c and 0x4d
61
62    Datasheet: Publicly available at the ON Semiconductor website
63
64	       https://www.onsemi.com/PowerSolutions/product.do?id=ADT7461
65
66  * Analog Devices ADT7461A
67
68    Prefix: 'adt7461a'
69
70    Addresses scanned: I2C 0x4c and 0x4d
71
72    Datasheet: Publicly available at the ON Semiconductor website
73
74	       https://www.onsemi.com/PowerSolutions/product.do?id=ADT7461A
75
76  * ON Semiconductor NCT1008
77
78    Prefix: 'nct1008'
79
80    Addresses scanned: I2C 0x4c and 0x4d
81
82    Datasheet: Publicly available at the ON Semiconductor website
83
84	       https://www.onsemi.com/PowerSolutions/product.do?id=NCT1008
85
86  * Maxim MAX6646
87
88    Prefix: 'max6646'
89
90    Addresses scanned: I2C 0x4d
91
92    Datasheet: Publicly available at the Maxim website
93
94	       http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
95
96  * Maxim MAX6647
97
98    Prefix: 'max6646'
99
100    Addresses scanned: I2C 0x4e
101
102    Datasheet: Publicly available at the Maxim website
103
104	       http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
105
106  * Maxim MAX6648
107
108    Prefix: 'max6646'
109
110    Addresses scanned: I2C 0x4c
111
112    Datasheet: Publicly available at the Maxim website
113
114	       http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3500
115
116  * Maxim MAX6649
117
118    Prefix: 'max6646'
119
120    Addresses scanned: I2C 0x4c
121
122    Datasheet: Publicly available at the Maxim website
123
124	       http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3497
125
126  * Maxim MAX6654
127
128    Prefix: 'max6654'
129
130    Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
131
132			   0x4c, 0x4d and 0x4e
133
134    Datasheet: Publicly available at the Maxim website
135
136	       https://www.maximintegrated.com/en/products/sensors/MAX6654.html
137
138  * Maxim MAX6657
139
140    Prefix: 'max6657'
141
142    Addresses scanned: I2C 0x4c
143
144    Datasheet: Publicly available at the Maxim website
145
146	       http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578
147
148  * Maxim MAX6658
149
150    Prefix: 'max6657'
151
152    Addresses scanned: I2C 0x4c
153
154    Datasheet: Publicly available at the Maxim website
155
156	       http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578
157
158  * Maxim MAX6659
159
160    Prefix: 'max6659'
161
162    Addresses scanned: I2C 0x4c, 0x4d, 0x4e
163
164    Datasheet: Publicly available at the Maxim website
165
166	       http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2578
167
168  * Maxim MAX6680
169
170    Prefix: 'max6680'
171
172    Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
173
174			   0x4c, 0x4d and 0x4e
175
176    Datasheet: Publicly available at the Maxim website
177
178	       http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3370
179
180  * Maxim MAX6681
181
182    Prefix: 'max6680'
183
184    Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
185
186			   0x4c, 0x4d and 0x4e
187
188    Datasheet: Publicly available at the Maxim website
189
190	       http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3370
191
192  * Maxim MAX6692
193
194    Prefix: 'max6646'
195
196    Addresses scanned: I2C 0x4c
197
198    Datasheet: Publicly available at the Maxim website
199
200	       http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3500
201
202  * Maxim MAX6695
203
204    Prefix: 'max6695'
205
206    Addresses scanned: I2C 0x18
207
208    Datasheet: Publicly available at the Maxim website
209
210	       http://www.maxim-ic.com/datasheet/index.mvp/id/4199
211
212  * Maxim MAX6696
213
214    Prefix: 'max6695'
215
216    Addresses scanned: I2C 0x18, 0x19, 0x1a, 0x29, 0x2a, 0x2b,
217
218			   0x4c, 0x4d and 0x4e
219
220    Datasheet: Publicly available at the Maxim website
221
222	       http://www.maxim-ic.com/datasheet/index.mvp/id/4199
223
224  * Winbond/Nuvoton W83L771W/G
225
226    Prefix: 'w83l771'
227
228    Addresses scanned: I2C 0x4c
229
230    Datasheet: No longer available
231
232  * Winbond/Nuvoton W83L771AWG/ASG
233
234    Prefix: 'w83l771'
235
236    Addresses scanned: I2C 0x4c
237
238    Datasheet: Not publicly available, can be requested from Nuvoton
239
240  * Philips/NXP SA56004X
241
242    Prefix: 'sa56004'
243
244    Addresses scanned: I2C 0x48 through 0x4F
245
246    Datasheet: Publicly available at NXP website
247
248	       http://ics.nxp.com/products/interface/datasheet/sa56004x.pdf
249
250  * GMT G781
251
252    Prefix: 'g781'
253
254    Addresses scanned: I2C 0x4c, 0x4d
255
256    Datasheet: Not publicly available from GMT
257
258  * Texas Instruments TMP451
259
260    Prefix: 'tmp451'
261
262    Addresses scanned: I2C 0x4c
263
264    Datasheet: Publicly available at TI website
265
266	       https://www.ti.com/litv/pdf/sbos686
267
268  * Texas Instruments TMP461
269
270    Prefix: 'tmp461'
271
272    Addresses scanned: I2C 0x48 through 0x4F
273
274    Datasheet: Publicly available at TI website
275
276	       https://www.ti.com/lit/gpn/tmp461
277
278Author: Jean Delvare <jdelvare@suse.de>
279
280
281Description
282-----------
283
284The LM90 is a digital temperature sensor. It senses its own temperature as
285well as the temperature of up to one external diode. It is compatible
286with many other devices, many of which are supported by this driver.
287
288Note that there is no easy way to differentiate between the MAX6657,
289MAX6658 and MAX6659 variants. The extra features of the MAX6659 are only
290supported by this driver if the chip is located at address 0x4d or 0x4e,
291or if the chip type is explicitly selected as max6659.
292The MAX6680 and MAX6681 only differ in their pinout, therefore they obviously
293can't (and don't need to) be distinguished.
294
295The specificity of this family of chipsets over the ADM1021/LM84
296family is that it features critical limits with hysteresis, and an
297increased resolution of the remote temperature measurement.
298
299The different chipsets of the family are not strictly identical, although
300very similar. For reference, here comes a non-exhaustive list of specific
301features:
302
303LM90:
304  * Filter and alert configuration register at 0xBF.
305  * ALERT is triggered by temperatures over critical limits.
306
307LM86 and LM89:
308  * Same as LM90
309  * Better external channel accuracy
310
311LM99:
312  * Same as LM89
313  * External temperature shifted by 16 degrees down
314
315ADM1032:
316  * Consecutive alert register at 0x22.
317  * Conversion averaging.
318  * Up to 64 conversions/s.
319  * ALERT is triggered by open remote sensor.
320  * SMBus PEC support for Write Byte and Receive Byte transactions.
321
322ADT7461, ADT7461A, NCT1008:
323  * Extended temperature range (breaks compatibility)
324  * Lower resolution for remote temperature
325
326MAX6654:
327  * Better local resolution
328  * Selectable address
329  * Remote sensor type selection
330  * Extended temperature range
331  * Extended resolution only available when conversion rate <= 1 Hz
332
333MAX6657 and MAX6658:
334  * Better local resolution
335  * Remote sensor type selection
336
337MAX6659:
338  * Better local resolution
339  * Selectable address
340  * Second critical temperature limit
341  * Remote sensor type selection
342
343MAX6680 and MAX6681:
344  * Selectable address
345  * Remote sensor type selection
346
347MAX6695 and MAX6696:
348  * Better local resolution
349  * Selectable address (max6696)
350  * Second critical temperature limit
351  * Two remote sensors
352
353W83L771W/G
354  * The G variant is lead-free, otherwise similar to the W.
355  * Filter and alert configuration register at 0xBF
356  * Moving average (depending on conversion rate)
357
358W83L771AWG/ASG
359  * Successor of the W83L771W/G, same features.
360  * The AWG and ASG variants only differ in package format.
361  * Diode ideality factor configuration (remote sensor) at 0xE3
362
363SA56004X:
364  * Better local resolution
365
366All temperature values are given in degrees Celsius. Resolution
367is 1.0 degree for the local temperature, 0.125 degree for the remote
368temperature, except for the MAX6654, MAX6657, MAX6658 and MAX6659 which have
369a resolution of 0.125 degree for both temperatures.
370
371Each sensor has its own high and low limits, plus a critical limit.
372Additionally, there is a relative hysteresis value common to both critical
373values. To make life easier to user-space applications, two absolute values
374are exported, one for each channel, but these values are of course linked.
375Only the local hysteresis can be set from user-space, and the same delta
376applies to the remote hysteresis.
377
378The lm90 driver will not update its values more frequently than configured with
379the update_interval attribute; reading them more often will do no harm, but will
380return 'old' values.
381
382SMBus Alert Support
383-------------------
384
385This driver has basic support for SMBus alert. When an alert is received,
386the status register is read and the faulty temperature channel is logged.
387
388The Analog Devices chips (ADM1032, ADT7461 and ADT7461A) and ON
389Semiconductor chips (NCT1008) do not implement the SMBus alert protocol
390properly so additional care is needed: the ALERT output is disabled when
391an alert is received, and is re-enabled only when the alarm is gone.
392Otherwise the chip would block alerts from other chips in the bus as long
393as the alarm is active.
394
395PEC Support
396-----------
397
398The ADM1032 is the only chip of the family which supports PEC. It does
399not support PEC on all transactions though, so some care must be taken.
400
401When reading a register value, the PEC byte is computed and sent by the
402ADM1032 chip. However, in the case of a combined transaction (SMBus Read
403Byte), the ADM1032 computes the CRC value over only the second half of
404the message rather than its entirety, because it thinks the first half
405of the message belongs to a different transaction. As a result, the CRC
406value differs from what the SMBus master expects, and all reads fail.
407
408For this reason, the lm90 driver will enable PEC for the ADM1032 only if
409the bus supports the SMBus Send Byte and Receive Byte transaction types.
410These transactions will be used to read register values, instead of
411SMBus Read Byte, and PEC will work properly.
412
413Additionally, the ADM1032 doesn't support SMBus Send Byte with PEC.
414Instead, it will try to write the PEC value to the register (because the
415SMBus Send Byte transaction with PEC is similar to a Write Byte transaction
416without PEC), which is not what we want. Thus, PEC is explicitly disabled
417on SMBus Send Byte transactions in the lm90 driver.
418
419PEC on byte data transactions represents a significant increase in bandwidth
420usage (+33% for writes, +25% for reads) in normal conditions. With the need
421to use two SMBus transaction for reads, this overhead jumps to +50%. Worse,
422two transactions will typically mean twice as much delay waiting for
423transaction completion, effectively doubling the register cache refresh time.
424I guess reliability comes at a price, but it's quite expensive this time.
425
426So, as not everyone might enjoy the slowdown, PEC can be disabled through
427sysfs. Just write 0 to the "pec" file and PEC will be disabled. Write 1
428to that file to enable PEC again.
429