linux/Documentation/hwmon/it87
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   1Kernel driver it87
   2==================
   3
   4Supported chips:
   5  * IT8705F
   6    Prefix: 'it87'
   7    Addresses scanned: from Super I/O config space (8 I/O ports)
   8    Datasheet: Once publicly available at the ITE website, but no longer
   9  * IT8712F
  10    Prefix: 'it8712'
  11    Addresses scanned: from Super I/O config space (8 I/O ports)
  12    Datasheet: Once publicly available at the ITE website, but no longer
  13  * IT8716F/IT8726F
  14    Prefix: 'it8716'
  15    Addresses scanned: from Super I/O config space (8 I/O ports)
  16    Datasheet: Once publicly available at the ITE website, but no longer
  17  * IT8718F
  18    Prefix: 'it8718'
  19    Addresses scanned: from Super I/O config space (8 I/O ports)
  20    Datasheet: Once publicly available at the ITE website, but no longer
  21  * IT8720F
  22    Prefix: 'it8720'
  23    Addresses scanned: from Super I/O config space (8 I/O ports)
  24    Datasheet: Not publicly available
  25  * IT8721F/IT8758E
  26    Prefix: 'it8721'
  27    Addresses scanned: from Super I/O config space (8 I/O ports)
  28    Datasheet: Not publicly available
  29  * IT8728F
  30    Prefix: 'it8728'
  31    Addresses scanned: from Super I/O config space (8 I/O ports)
  32    Datasheet: Not publicly available
  33  * IT8782F
  34    Prefix: 'it8782'
  35    Addresses scanned: from Super I/O config space (8 I/O ports)
  36    Datasheet: Not publicly available
  37  * IT8783E/F
  38    Prefix: 'it8783'
  39    Addresses scanned: from Super I/O config space (8 I/O ports)
  40    Datasheet: Not publicly available
  41  * SiS950   [clone of IT8705F]
  42    Prefix: 'it87'
  43    Addresses scanned: from Super I/O config space (8 I/O ports)
  44    Datasheet: No longer be available
  45
  46Authors:
  47    Christophe Gauthron
  48    Jean Delvare <khali@linux-fr.org>
  49
  50
  51Module Parameters
  52-----------------
  53
  54* update_vbat: int
  55
  56  0 if vbat should report power on value, 1 if vbat should be updated after
  57  each read. Default is 0. On some boards the battery voltage is provided
  58  by either the battery or the onboard power supply. Only the first reading
  59  at power on will be the actual battery voltage (which the chip does
  60  automatically). On other boards the battery voltage is always fed to
  61  the chip so can be read at any time. Excessive reading may decrease
  62  battery life but no information is given in the datasheet.
  63
  64* fix_pwm_polarity int
  65
  66  Force PWM polarity to active high (DANGEROUS). Some chips are
  67  misconfigured by BIOS - PWM values would be inverted. This option tries
  68  to fix this. Please contact your BIOS manufacturer and ask him for fix.
  69
  70
  71Hardware Interfaces
  72-------------------
  73
  74All the chips supported by this driver are LPC Super-I/O chips, accessed
  75through the LPC bus (ISA-like I/O ports). The IT8712F additionally has an
  76SMBus interface to the hardware monitoring functions. This driver no
  77longer supports this interface though, as it is slower and less reliable
  78than the ISA access, and was only available on a small number of
  79motherboard models.
  80
  81
  82Description
  83-----------
  84
  85This driver implements support for the IT8705F, IT8712F, IT8716F,
  86IT8718F, IT8720F, IT8721F, IT8726F, IT8728F, IT8758E, IT8781F, IT8782F,
  87IT8783E/F, and SiS950 chips.
  88
  89These chips are 'Super I/O chips', supporting floppy disks, infrared ports,
  90joysticks and other miscellaneous stuff. For hardware monitoring, they
  91include an 'environment controller' with 3 temperature sensors, 3 fan
  92rotation speed sensors, 8 voltage sensors, associated alarms, and chassis
  93intrusion detection.
  94
  95The IT8712F and IT8716F additionally feature VID inputs, used to report
  96the Vcore voltage of the processor. The early IT8712F have 5 VID pins,
  97the IT8716F and late IT8712F have 6. They are shared with other functions
  98though, so the functionality may not be available on a given system.
  99
 100The IT8718F and IT8720F also features VID inputs (up to 8 pins) but the value
 101is stored in the Super-I/O configuration space. Due to technical limitations,
 102this value can currently only be read once at initialization time, so
 103the driver won't notice and report changes in the VID value. The two
 104upper VID bits share their pins with voltage inputs (in5 and in6) so you
 105can't have both on a given board.
 106
 107The IT8716F, IT8718F, IT8720F, IT8721F/IT8758E and later IT8712F revisions
 108have support for 2 additional fans. The additional fans are supported by the
 109driver.
 110
 111The IT8716F, IT8718F, IT8720F, IT8721F/IT8758E, IT8782F, IT8783E/F, and late
 112IT8712F and IT8705F also have optional 16-bit tachometer counters for fans 1 to
 1133. This is better (no more fan clock divider mess) but not compatible with the
 114older chips and revisions. The 16-bit tachometer mode is enabled by the driver
 115when one of the above chips is detected.
 116
 117The IT8726F is just bit enhanced IT8716F with additional hardware
 118for AMD power sequencing. Therefore the chip will appear as IT8716F
 119to userspace applications.
 120
 121The IT8728F is considered compatible with the IT8721F, until a datasheet
 122becomes available (hopefully.)
 123
 124Temperatures are measured in degrees Celsius. An alarm is triggered once
 125when the Overtemperature Shutdown limit is crossed.
 126
 127Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
 128triggered if the rotation speed has dropped below a programmable limit. When
 12916-bit tachometer counters aren't used, fan readings can be divided by
 130a programmable divider (1, 2, 4 or 8) to give the readings more range or
 131accuracy. With a divider of 2, the lowest representable value is around
 1322600 RPM. Not all RPM values can accurately be represented, so some rounding
 133is done.
 134
 135Voltage sensors (also known as IN sensors) report their values in volts. An
 136alarm is triggered if the voltage has crossed a programmable minimum or
 137maximum limit. Note that minimum in this case always means 'closest to
 138zero'; this is important for negative voltage measurements. All voltage
 139inputs can measure voltages between 0 and 4.08 volts, with a resolution of
 1400.016 volt (except IT8721F/IT8758E and IT8728F: 0.012 volt.) The battery
 141voltage in8 does not have limit registers.
 142
 143On the IT8721F/IT8758E, IT8782F, and IT8783E/F, some voltage inputs are
 144internal and scaled inside the chip (in7 (optional for IT8782F and IT8783E/F),
 145in8 and optionally in3). The driver handles this transparently so user-space
 146doesn't have to care.
 147
 148The VID lines (IT8712F/IT8716F/IT8718F/IT8720F) encode the core voltage value:
 149the voltage level your processor should work with. This is hardcoded by
 150the mainboard and/or processor itself. It is a value in volts.
 151
 152If an alarm triggers, it will remain triggered until the hardware register
 153is read at least once. This means that the cause for the alarm may already
 154have disappeared! Note that in the current implementation, all hardware
 155registers are read whenever any data is read (unless it is less than 1.5
 156seconds since the last update). This means that you can easily miss
 157once-only alarms.
 158
 159Out-of-limit readings can also result in beeping, if the chip is properly
 160wired and configured. Beeping can be enabled or disabled per sensor type
 161(temperatures, voltages and fans.)
 162
 163The IT87xx only updates its values each 1.5 seconds; reading it more often
 164will do no harm, but will return 'old' values.
 165
 166To change sensor N to a thermistor, 'echo 4 > tempN_type' where N is 1, 2,
 167or 3. To change sensor N to a thermal diode, 'echo 3 > tempN_type'.
 168Give 0 for unused sensor. Any other value is invalid. To configure this at
 169startup, consult lm_sensors's /etc/sensors.conf. (4 = thermistor;
 1703 = thermal diode)
 171
 172
 173Fan speed control
 174-----------------
 175
 176The fan speed control features are limited to manual PWM mode. Automatic
 177"Smart Guardian" mode control handling is only implemented for older chips
 178(see below.) However if you want to go for "manual mode" just write 1 to
 179pwmN_enable.
 180
 181If you are only able to control the fan speed with very small PWM values,
 182try lowering the PWM base frequency (pwm1_freq). Depending on the fan,
 183it may give you a somewhat greater control range. The same frequency is
 184used to drive all fan outputs, which is why pwm2_freq and pwm3_freq are
 185read-only.
 186
 187
 188Automatic fan speed control (old interface)
 189-------------------------------------------
 190
 191The driver supports the old interface to automatic fan speed control
 192which is implemented by IT8705F chips up to revision F and IT8712F
 193chips up to revision G.
 194
 195This interface implements 4 temperature vs. PWM output trip points.
 196The PWM output of trip point 4 is always the maximum value (fan running
 197at full speed) while the PWM output of the other 3 trip points can be
 198freely chosen. The temperature of all 4 trip points can be freely chosen.
 199Additionally, trip point 1 has an hysteresis temperature attached, to
 200prevent fast switching between fan on and off.
 201
 202The chip automatically computes the PWM output value based on the input
 203temperature, based on this simple rule: if the temperature value is
 204between trip point N and trip point N+1 then the PWM output value is
 205the one of trip point N. The automatic control mode is less flexible
 206than the manual control mode, but it reacts faster, is more robust and
 207doesn't use CPU cycles.
 208
 209Trip points must be set properly before switching to automatic fan speed
 210control mode. The driver will perform basic integrity checks before
 211actually switching to automatic control mode.
 212
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