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 http://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 http://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 http://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 http://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 http://www.ti.com/litv/pdf/sbos686 267 268Author: Jean Delvare <jdelvare@suse.de> 269 270 271Description 272----------- 273 274The LM90 is a digital temperature sensor. It senses its own temperature as 275well as the temperature of up to one external diode. It is compatible 276with many other devices, many of which are supported by this driver. 277 278Note that there is no easy way to differentiate between the MAX6657, 279MAX6658 and MAX6659 variants. The extra features of the MAX6659 are only 280supported by this driver if the chip is located at address 0x4d or 0x4e, 281or if the chip type is explicitly selected as max6659. 282The MAX6680 and MAX6681 only differ in their pinout, therefore they obviously 283can't (and don't need to) be distinguished. 284 285The specificity of this family of chipsets over the ADM1021/LM84 286family is that it features critical limits with hysteresis, and an 287increased resolution of the remote temperature measurement. 288 289The different chipsets of the family are not strictly identical, although 290very similar. For reference, here comes a non-exhaustive list of specific 291features: 292 293LM90: 294 * Filter and alert configuration register at 0xBF. 295 * ALERT is triggered by temperatures over critical limits. 296 297LM86 and LM89: 298 * Same as LM90 299 * Better external channel accuracy 300 301LM99: 302 * Same as LM89 303 * External temperature shifted by 16 degrees down 304 305ADM1032: 306 * Consecutive alert register at 0x22. 307 * Conversion averaging. 308 * Up to 64 conversions/s. 309 * ALERT is triggered by open remote sensor. 310 * SMBus PEC support for Write Byte and Receive Byte transactions. 311 312ADT7461, ADT7461A, NCT1008: 313 * Extended temperature range (breaks compatibility) 314 * Lower resolution for remote temperature 315 316MAX6654: 317 * Better local resolution 318 * Selectable address 319 * Remote sensor type selection 320 * Extended temperature range 321 * Extended resolution only available when conversion rate <= 1 Hz 322 323MAX6657 and MAX6658: 324 * Better local resolution 325 * Remote sensor type selection 326 327MAX6659: 328 * Better local resolution 329 * Selectable address 330 * Second critical temperature limit 331 * Remote sensor type selection 332 333MAX6680 and MAX6681: 334 * Selectable address 335 * Remote sensor type selection 336 337MAX6695 and MAX6696: 338 * Better local resolution 339 * Selectable address (max6696) 340 * Second critical temperature limit 341 * Two remote sensors 342 343W83L771W/G 344 * The G variant is lead-free, otherwise similar to the W. 345 * Filter and alert configuration register at 0xBF 346 * Moving average (depending on conversion rate) 347 348W83L771AWG/ASG 349 * Successor of the W83L771W/G, same features. 350 * The AWG and ASG variants only differ in package format. 351 * Diode ideality factor configuration (remote sensor) at 0xE3 352 353SA56004X: 354 * Better local resolution 355 356All temperature values are given in degrees Celsius. Resolution 357is 1.0 degree for the local temperature, 0.125 degree for the remote 358temperature, except for the MAX6654, MAX6657, MAX6658 and MAX6659 which have 359a resolution of 0.125 degree for both temperatures. 360 361Each sensor has its own high and low limits, plus a critical limit. 362Additionally, there is a relative hysteresis value common to both critical 363values. To make life easier to user-space applications, two absolute values 364are exported, one for each channel, but these values are of course linked. 365Only the local hysteresis can be set from user-space, and the same delta 366applies to the remote hysteresis. 367 368The lm90 driver will not update its values more frequently than configured with 369the update_interval attribute; reading them more often will do no harm, but will 370return 'old' values. 371 372SMBus Alert Support 373------------------- 374 375This driver has basic support for SMBus alert. When an alert is received, 376the status register is read and the faulty temperature channel is logged. 377 378The Analog Devices chips (ADM1032, ADT7461 and ADT7461A) and ON 379Semiconductor chips (NCT1008) do not implement the SMBus alert protocol 380properly so additional care is needed: the ALERT output is disabled when 381an alert is received, and is re-enabled only when the alarm is gone. 382Otherwise the chip would block alerts from other chips in the bus as long 383as the alarm is active. 384 385PEC Support 386----------- 387 388The ADM1032 is the only chip of the family which supports PEC. It does 389not support PEC on all transactions though, so some care must be taken. 390 391When reading a register value, the PEC byte is computed and sent by the 392ADM1032 chip. However, in the case of a combined transaction (SMBus Read 393Byte), the ADM1032 computes the CRC value over only the second half of 394the message rather than its entirety, because it thinks the first half 395of the message belongs to a different transaction. As a result, the CRC 396value differs from what the SMBus master expects, and all reads fail. 397 398For this reason, the lm90 driver will enable PEC for the ADM1032 only if 399the bus supports the SMBus Send Byte and Receive Byte transaction types. 400These transactions will be used to read register values, instead of 401SMBus Read Byte, and PEC will work properly. 402 403Additionally, the ADM1032 doesn't support SMBus Send Byte with PEC. 404Instead, it will try to write the PEC value to the register (because the 405SMBus Send Byte transaction with PEC is similar to a Write Byte transaction 406without PEC), which is not what we want. Thus, PEC is explicitly disabled 407on SMBus Send Byte transactions in the lm90 driver. 408 409PEC on byte data transactions represents a significant increase in bandwidth 410usage (+33% for writes, +25% for reads) in normal conditions. With the need 411to use two SMBus transaction for reads, this overhead jumps to +50%. Worse, 412two transactions will typically mean twice as much delay waiting for 413transaction completion, effectively doubling the register cache refresh time. 414I guess reliability comes at a price, but it's quite expensive this time. 415 416So, as not everyone might enjoy the slowdown, PEC can be disabled through 417sysfs. Just write 0 to the "pec" file and PEC will be disabled. Write 1 418to that file to enable PEC again. 419