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Linux/Documentation/hwmon/it87.rst

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  1 Kernel driver it87
  2 ==================
  3 
  4 Supported chips:
  5 
  6   * IT8603E/IT8623E
  7 
  8     Prefix: 'it8603'
  9 
 10     Addresses scanned: from Super I/O config space (8 I/O ports)
 11 
 12     Datasheet: Not publicly available
 13 
 14   * IT8620E
 15 
 16     Prefix: 'it8620'
 17 
 18     Addresses scanned: from Super I/O config space (8 I/O ports)
 19 
 20   * IT8628E
 21 
 22     Prefix: 'it8628'
 23 
 24     Addresses scanned: from Super I/O config space (8 I/O ports)
 25 
 26     Datasheet: Not publicly available
 27 
 28   * IT8705F
 29 
 30     Prefix: 'it87'
 31 
 32     Addresses scanned: from Super I/O config space (8 I/O ports)
 33 
 34     Datasheet: Once publicly available at the ITE website, but no longer
 35 
 36   * IT8712F
 37 
 38     Prefix: 'it8712'
 39 
 40     Addresses scanned: from Super I/O config space (8 I/O ports)
 41 
 42     Datasheet: Once publicly available at the ITE website, but no longer
 43 
 44   * IT8716F/IT8726F
 45 
 46     Prefix: 'it8716'
 47 
 48     Addresses scanned: from Super I/O config space (8 I/O ports)
 49 
 50     Datasheet: Once publicly available at the ITE website, but no longer
 51 
 52   * IT8718F
 53 
 54     Prefix: 'it8718'
 55 
 56     Addresses scanned: from Super I/O config space (8 I/O ports)
 57 
 58     Datasheet: Once publicly available at the ITE website, but no longer
 59 
 60   * IT8720F
 61 
 62     Prefix: 'it8720'
 63 
 64     Addresses scanned: from Super I/O config space (8 I/O ports)
 65 
 66     Datasheet: Not publicly available
 67 
 68   * IT8721F/IT8758E
 69 
 70     Prefix: 'it8721'
 71 
 72     Addresses scanned: from Super I/O config space (8 I/O ports)
 73 
 74     Datasheet: Not publicly available
 75 
 76   * IT8728F
 77 
 78     Prefix: 'it8728'
 79 
 80     Addresses scanned: from Super I/O config space (8 I/O ports)
 81 
 82     Datasheet: Not publicly available
 83 
 84   * IT8732F
 85 
 86     Prefix: 'it8732'
 87 
 88     Addresses scanned: from Super I/O config space (8 I/O ports)
 89 
 90     Datasheet: Not publicly available
 91 
 92   * IT8771E
 93 
 94     Prefix: 'it8771'
 95 
 96     Addresses scanned: from Super I/O config space (8 I/O ports)
 97 
 98     Datasheet: Not publicly available
 99 
100   * IT8772E
101 
102     Prefix: 'it8772'
103 
104     Addresses scanned: from Super I/O config space (8 I/O ports)
105 
106     Datasheet: Not publicly available
107 
108   * IT8781F
109 
110     Prefix: 'it8781'
111 
112     Addresses scanned: from Super I/O config space (8 I/O ports)
113 
114     Datasheet: Not publicly available
115 
116   * IT8782F
117 
118     Prefix: 'it8782'
119 
120     Addresses scanned: from Super I/O config space (8 I/O ports)
121 
122     Datasheet: Not publicly available
123 
124   * IT8783E/F
125 
126     Prefix: 'it8783'
127 
128     Addresses scanned: from Super I/O config space (8 I/O ports)
129 
130     Datasheet: Not publicly available
131 
132   * IT8786E
133 
134     Prefix: 'it8786'
135 
136     Addresses scanned: from Super I/O config space (8 I/O ports)
137 
138     Datasheet: Not publicly available
139 
140   * IT8790E
141 
142     Prefix: 'it8790'
143 
144     Addresses scanned: from Super I/O config space (8 I/O ports)
145 
146     Datasheet: Not publicly available
147 
148   * IT8792E/IT8795E
149 
150     Prefix: 'it8792'
151 
152     Addresses scanned: from Super I/O config space (8 I/O ports)
153 
154     Datasheet: Not publicly available
155 
156   * IT87952E
157 
158     Prefix: 'it87952'
159 
160     Addresses scanned: from Super I/O config space (8 I/O ports)
161 
162     Datasheet: Not publicly available
163 
164   * SiS950   [clone of IT8705F]
165 
166     Prefix: 'it87'
167 
168     Addresses scanned: from Super I/O config space (8 I/O ports)
169 
170     Datasheet: No longer be available
171 
172 
173 Authors:
174     - Christophe Gauthron
175     - Jean Delvare <jdelvare@suse.de>
176 
177 
178 Module Parameters
179 -----------------
180 
181 * update_vbat bool
182     0 if vbat should report power on value, 1 if vbat should be updated after
183     each read. Default is 0. On some boards the battery voltage is provided
184     by either the battery or the onboard power supply. Only the first reading
185     at power on will be the actual battery voltage (which the chip does
186     automatically). On other boards the battery voltage is always fed to
187     the chip so can be read at any time. Excessive reading may decrease
188     battery life but no information is given in the datasheet.
189 
190 * fix_pwm_polarity bool
191     Force PWM polarity to active high (DANGEROUS). Some chips are
192     misconfigured by BIOS - PWM values would be inverted. This option tries
193     to fix this. Please contact your BIOS manufacturer and ask him for fix.
194 
195 * force_id short, short
196 
197   Force multiple chip ID to specified value, separated by ','.
198   For example "force_id=0x8689,0x8633".  A value of 0 is ignored
199   for that chip.
200   Note: A single force_id value (e.g. "force_id=0x8689") is used for
201   all chips, to only set the first chip use "force_id=0x8689,0".
202   Should only be used for testing.
203 
204 * ignore_resource_conflict bool
205 
206   Similar to acpi_enforce_resources=lax, but only affects this driver.
207   ACPI resource conflicts are ignored if this parameter is provided and
208   set to 1.
209   Provided since there are reports that system-wide acpi_enfore_resources=lax
210   can result in boot failures on some systems.
211   Note: This is inherently risky since it means that both ACPI and this driver
212   may access the chip at the same time. This can result in race conditions and,
213   worst case, result in unexpected system reboots.
214 
215 
216 Hardware Interfaces
217 -------------------
218 
219 All the chips supported by this driver are LPC Super-I/O chips, accessed
220 through the LPC bus (ISA-like I/O ports). The IT8712F additionally has an
221 SMBus interface to the hardware monitoring functions. This driver no
222 longer supports this interface though, as it is slower and less reliable
223 than the ISA access, and was only available on a small number of
224 motherboard models.
225 
226 
227 Description
228 -----------
229 
230 This driver implements support for the IT8603E, IT8620E, IT8623E, IT8628E,
231 IT8705F, IT8712F, IT8716F, IT8718F, IT8720F, IT8721F, IT8726F, IT8728F, IT8732F,
232 IT8758E, IT8771E, IT8772E, IT8781F, IT8782F, IT8783E/F, IT8786E, IT8790E,
233 IT8792E/IT8795E, IT87952E and SiS950 chips.
234 
235 These chips are 'Super I/O chips', supporting floppy disks, infrared ports,
236 joysticks and other miscellaneous stuff. For hardware monitoring, they
237 include an 'environment controller' with 3 temperature sensors, 3 fan
238 rotation speed sensors, 8 voltage sensors, associated alarms, and chassis
239 intrusion detection.
240 
241 The IT8712F and IT8716F additionally feature VID inputs, used to report
242 the Vcore voltage of the processor. The early IT8712F have 5 VID pins,
243 the IT8716F and late IT8712F have 6. They are shared with other functions
244 though, so the functionality may not be available on a given system.
245 
246 The IT8718F and IT8720F also features VID inputs (up to 8 pins) but the value
247 is stored in the Super-I/O configuration space. Due to technical limitations,
248 this value can currently only be read once at initialization time, so
249 the driver won't notice and report changes in the VID value. The two
250 upper VID bits share their pins with voltage inputs (in5 and in6) so you
251 can't have both on a given board.
252 
253 The IT8716F, IT8718F, IT8720F, IT8721F/IT8758E and later IT8712F revisions
254 have support for 2 additional fans. The additional fans are supported by the
255 driver.
256 
257 The IT8716F, IT8718F, IT8720F, IT8721F/IT8758E, IT8732F, IT8781F, IT8782F,
258 IT8783E/F, and late IT8712F and IT8705F also have optional 16-bit tachometer
259 counters for fans 1 to 3. This is better (no more fan clock divider mess) but
260 not compatible with the older chips and revisions. The 16-bit tachometer mode
261 is enabled by the driver when one of the above chips is detected.
262 
263 The IT8726F is just bit enhanced IT8716F with additional hardware
264 for AMD power sequencing. Therefore the chip will appear as IT8716F
265 to userspace applications.
266 
267 The IT8728F, IT8771E, and IT8772E are considered compatible with the IT8721F,
268 until a datasheet becomes available (hopefully.)
269 
270 The IT8603E/IT8623E is a custom design, hardware monitoring part is similar to
271 IT8728F. It only supports 3 fans, 16-bit fan mode, and the full speed mode
272 of the fan is not supported (value 0 of pwmX_enable).
273 
274 The IT8620E and IT8628E are custom designs, hardware monitoring part is similar
275 to IT8728F. It only supports 16-bit fan mode. Both chips support up to 6 fans.
276 
277 The IT8790E, IT8792E/IT8795E and IT87952E support up to 3 fans. 16-bit fan
278 mode is always enabled.
279 
280 The IT8732F supports a closed-loop mode for fan control, but this is not
281 currently implemented by the driver.
282 
283 Temperatures are measured in degrees Celsius. An alarm is triggered once
284 when the Overtemperature Shutdown limit is crossed.
285 
286 Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
287 triggered if the rotation speed has dropped below a programmable limit. When
288 16-bit tachometer counters aren't used, fan readings can be divided by
289 a programmable divider (1, 2, 4 or 8) to give the readings more range or
290 accuracy. With a divider of 2, the lowest representable value is around
291 2600 RPM. Not all RPM values can accurately be represented, so some rounding
292 is done.
293 
294 Voltage sensors (also known as IN sensors) report their values in volts. An
295 alarm is triggered if the voltage has crossed a programmable minimum or
296 maximum limit. Note that minimum in this case always means 'closest to
297 zero'; this is important for negative voltage measurements. On most chips, all
298 voltage inputs can measure voltages between 0 and 4.08 volts, with a resolution
299 of 0.016 volt.  IT8603E, IT8721F/IT8758E and IT8728F can measure between 0 and
300 3.06 volts, with a resolution of 0.012 volt.  IT8732F can measure between 0 and
301 2.8 volts with a resolution of 0.0109 volt.  The battery voltage in8 does not
302 have limit registers.
303 
304 On the IT8603E, IT8620E, IT8628E, IT8721F/IT8758E, IT8732F, IT8781F, IT8782F,
305 and IT8783E/F, some voltage inputs are internal and scaled inside the chip:
306 * in3 (optional)
307 * in7 (optional for IT8781F, IT8782F, and IT8783E/F)
308 * in8 (always)
309 * in9 (relevant for IT8603E only)
310 The driver handles this transparently so user-space doesn't have to care.
311 
312 The VID lines (IT8712F/IT8716F/IT8718F/IT8720F) encode the core voltage value:
313 the voltage level your processor should work with. This is hardcoded by
314 the mainboard and/or processor itself. It is a value in volts.
315 
316 If an alarm triggers, it will remain triggered until the hardware register
317 is read at least once. This means that the cause for the alarm may already
318 have disappeared! Note that in the current implementation, all hardware
319 registers are read whenever any data is read (unless it is less than 1.5
320 seconds since the last update). This means that you can easily miss
321 once-only alarms.
322 
323 Out-of-limit readings can also result in beeping, if the chip is properly
324 wired and configured. Beeping can be enabled or disabled per sensor type
325 (temperatures, voltages and fans.)
326 
327 The IT87xx only updates its values each 1.5 seconds; reading it more often
328 will do no harm, but will return 'old' values.
329 
330 To change sensor N to a thermistor, 'echo 4 > tempN_type' where N is 1, 2,
331 or 3. To change sensor N to a thermal diode, 'echo 3 > tempN_type'.
332 Give 0 for unused sensor. Any other value is invalid. To configure this at
333 startup, consult lm_sensors's /etc/sensors.conf. (4 = thermistor;
334 3 = thermal diode)
335 
336 
337 Fan speed control
338 -----------------
339 
340 The fan speed control features are limited to manual PWM mode. Automatic
341 "Smart Guardian" mode control handling is only implemented for older chips
342 (see below.) However if you want to go for "manual mode" just write 1 to
343 pwmN_enable.
344 
345 If you are only able to control the fan speed with very small PWM values,
346 try lowering the PWM base frequency (pwm1_freq). Depending on the fan,
347 it may give you a somewhat greater control range. The same frequency is
348 used to drive all fan outputs, which is why pwm2_freq and pwm3_freq are
349 read-only.
350 
351 
352 Automatic fan speed control (old interface)
353 -------------------------------------------
354 
355 The driver supports the old interface to automatic fan speed control
356 which is implemented by IT8705F chips up to revision F and IT8712F
357 chips up to revision G.
358 
359 This interface implements 4 temperature vs. PWM output trip points.
360 The PWM output of trip point 4 is always the maximum value (fan running
361 at full speed) while the PWM output of the other 3 trip points can be
362 freely chosen. The temperature of all 4 trip points can be freely chosen.
363 Additionally, trip point 1 has an hysteresis temperature attached, to
364 prevent fast switching between fan on and off.
365 
366 The chip automatically computes the PWM output value based on the input
367 temperature, based on this simple rule: if the temperature value is
368 between trip point N and trip point N+1 then the PWM output value is
369 the one of trip point N. The automatic control mode is less flexible
370 than the manual control mode, but it reacts faster, is more robust and
371 doesn't use CPU cycles.
372 
373 Trip points must be set properly before switching to automatic fan speed
374 control mode. The driver will perform basic integrity checks before
375 actually switching to automatic control mode.
376 
377 
378 Temperature offset attributes
379 -----------------------------
380 
381 The driver supports temp[1-3]_offset sysfs attributes to adjust the reported
382 temperature for thermal diodes or diode-connected thermal transistors.
383 If a temperature sensor is configured for thermistors, the attribute values
384 are ignored. If the thermal sensor type is Intel PECI, the temperature offset
385 must be programmed to the critical CPU temperature.

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