Documentation/hwmon/it87

   1 Kernel driver it87
   2 ==================
   3
   4 Supported 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   * IT8771E
  34     Prefix: 'it8771'
  35     Addresses scanned: from Super I/O config space (8 I/O ports)
  36     Datasheet: Not publicly available
  37   * IT8772E
  38     Prefix: 'it8772'
  39     Addresses scanned: from Super I/O config space (8 I/O ports)
  40     Datasheet: Not publicly available
  41   * IT8782F
  42     Prefix: 'it8782'
  43     Addresses scanned: from Super I/O config space (8 I/O ports)
  44     Datasheet: Not publicly available
  45   * IT8783E/F
  46     Prefix: 'it8783'
  47     Addresses scanned: from Super I/O config space (8 I/O ports)
  48     Datasheet: Not publicly available
  49   * SiS950   [clone of IT8705F]
  50     Prefix: 'it87'
  51     Addresses scanned: from Super I/O config space (8 I/O ports)
  52     Datasheet: No longer be available
  53
  54 Authors:
  55     Christophe Gauthron
  56     Jean Delvare <khali@linux-fr.org>
  57
  58
  59 Module Parameters
  60 -----------------
  61
  62 * update_vbat: int
  63
  64   0 if vbat should report power on value, 1 if vbat should be updated after
  65   each read. Default is 0. On some boards the battery voltage is provided
  66   by either the battery or the onboard power supply. Only the first reading
  67   at power on will be the actual battery voltage (which the chip does
  68   automatically). On other boards the battery voltage is always fed to
  69   the chip so can be read at any time. Excessive reading may decrease
  70   battery life but no information is given in the datasheet.
  71
  72 * fix_pwm_polarity int
  73
  74   Force PWM polarity to active high (DANGEROUS). Some chips are
  75   misconfigured by BIOS - PWM values would be inverted. This option tries
  76   to fix this. Please contact your BIOS manufacturer and ask him for fix.
  77
  78
  79 Hardware Interfaces
  80 -------------------
  81
  82 All the chips supported by this driver are LPC Super-I/O chips, accessed
  83 through the LPC bus (ISA-like I/O ports). The IT8712F additionally has an
  84 SMBus interface to the hardware monitoring functions. This driver no
  85 longer supports this interface though, as it is slower and less reliable
  86 than the ISA access, and was only available on a small number of
  87 motherboard models.
  88
  89
  90 Description
  91 -----------
  92
  93 This driver implements support for the IT8705F, IT8712F, IT8716F,
  94 IT8718F, IT8720F, IT8721F, IT8726F, IT8728F, IT8758E, IT8771E, IT8772E,
  95 IT8782F, IT8783E/F, and SiS950 chips.
  96
  97 These chips are 'Super I/O chips', supporting floppy disks, infrared ports,
  98 joysticks and other miscellaneous stuff. For hardware monitoring, they
  99 include an 'environment controller' with 3 temperature sensors, 3 fan
 100 rotation speed sensors, 8 voltage sensors, associated alarms, and chassis
 101 intrusion detection.
 102
 103 The IT8712F and IT8716F additionally feature VID inputs, used to report
 104 the Vcore voltage of the processor. The early IT8712F have 5 VID pins,
 105 the IT8716F and late IT8712F have 6. They are shared with other functions
 106 though, so the functionality may not be available on a given system.
 107
 108 The IT8718F and IT8720F also features VID inputs (up to 8 pins) but the value
 109 is stored in the Super-I/O configuration space. Due to technical limitations,
 110 this value can currently only be read once at initialization time, so
 111 the driver won't notice and report changes in the VID value. The two
 112 upper VID bits share their pins with voltage inputs (in5 and in6) so you
 113 can't have both on a given board.
 114
 115 The IT8716F, IT8718F, IT8720F, IT8721F/IT8758E and later IT8712F revisions
 116 have support for 2 additional fans. The additional fans are supported by the
 117 driver.
 118
 119 The IT8716F, IT8718F, IT8720F, IT8721F/IT8758E, IT8782F, IT8783E/F, and late
 120 IT8712F and IT8705F also have optional 16-bit tachometer counters for fans 1 to
 121 3. This is better (no more fan clock divider mess) but not compatible with the
 122 older chips and revisions. The 16-bit tachometer mode is enabled by the driver
 123 when one of the above chips is detected.
 124
 125 The IT8726F is just bit enhanced IT8716F with additional hardware
 126 for AMD power sequencing. Therefore the chip will appear as IT8716F
 127 to userspace applications.
 128
 129 The IT8728F, IT8771E, and IT8772E are considered compatible with the IT8721F,
 130 until a datasheet becomes available (hopefully.)
 131
 132 Temperatures are measured in degrees Celsius. An alarm is triggered once
 133 when the Overtemperature Shutdown limit is crossed.
 134
 135 Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
 136 triggered if the rotation speed has dropped below a programmable limit. When
 137 16-bit tachometer counters aren't used, fan readings can be divided by
 138 a programmable divider (1, 2, 4 or 8) to give the readings more range or
 139 accuracy. With a divider of 2, the lowest representable value is around
 140 2600 RPM. Not all RPM values can accurately be represented, so some rounding
 141 is done.
 142
 143 Voltage sensors (also known as IN sensors) report their values in volts. An
 144 alarm is triggered if the voltage has crossed a programmable minimum or
 145 maximum limit. Note that minimum in this case always means 'closest to
 146 zero'; this is important for negative voltage measurements. All voltage
 147 inputs can measure voltages between 0 and 4.08 volts, with a resolution of
 148 0.016 volt (except IT8721F/IT8758E and IT8728F: 0.012 volt.) The battery
 149 voltage in8 does not have limit registers.
 150
 151 On the IT8721F/IT8758E, IT8782F, and IT8783E/F, some voltage inputs are
 152 internal and scaled inside the chip (in7 (optional for IT8782F and IT8783E/F),
 153 in8 and optionally in3). The driver handles this transparently so user-space
 154 doesn't have to care.
 155
 156 The VID lines (IT8712F/IT8716F/IT8718F/IT8720F) encode the core voltage value:
 157 the voltage level your processor should work with. This is hardcoded by
 158 the mainboard and/or processor itself. It is a value in volts.
 159
 160 If an alarm triggers, it will remain triggered until the hardware register
 161 is read at least once. This means that the cause for the alarm may already
 162 have disappeared! Note that in the current implementation, all hardware
 163 registers are read whenever any data is read (unless it is less than 1.5
 164 seconds since the last update). This means that you can easily miss
 165 once-only alarms.
 166
 167 Out-of-limit readings can also result in beeping, if the chip is properly
 168 wired and configured. Beeping can be enabled or disabled per sensor type
 169 (temperatures, voltages and fans.)
 170
 171 The IT87xx only updates its values each 1.5 seconds; reading it more often
 172 will do no harm, but will return 'old' values.
 173
 174 To change sensor N to a thermistor, 'echo 4 > tempN_type' where N is 1, 2,
 175 or 3. To change sensor N to a thermal diode, 'echo 3 > tempN_type'.
 176 Give 0 for unused sensor. Any other value is invalid. To configure this at
 177 startup, consult lm_sensors's /etc/sensors.conf. (4 = thermistor;
 178 3 = thermal diode)
 179
 180
 181 Fan speed control
 182 -----------------
 183
 184 The fan speed control features are limited to manual PWM mode. Automatic
 185 "Smart Guardian" mode control handling is only implemented for older chips
 186 (see below.) However if you want to go for "manual mode" just write 1 to
 187 pwmN_enable.
 188
 189 If you are only able to control the fan speed with very small PWM values,
 190 try lowering the PWM base frequency (pwm1_freq). Depending on the fan,
 191 it may give you a somewhat greater control range. The same frequency is
 192 used to drive all fan outputs, which is why pwm2_freq and pwm3_freq are
 193 read-only.
 194
 195
 196 Automatic fan speed control (old interface)
 197 -------------------------------------------
 198
 199 The driver supports the old interface to automatic fan speed control
 200 which is implemented by IT8705F chips up to revision F and IT8712F
 201 chips up to revision G.
 202
 203 This interface implements 4 temperature vs. PWM output trip points.
 204 The PWM output of trip point 4 is always the maximum value (fan running
 205 at full speed) while the PWM output of the other 3 trip points can be
 206 freely chosen. The temperature of all 4 trip points can be freely chosen.
 207 Additionally, trip point 1 has an hysteresis temperature attached, to
 208 prevent fast switching between fan on and off.
 209
 210 The chip automatically computes the PWM output value based on the input
 211 temperature, based on this simple rule: if the temperature value is
 212 between trip point N and trip point N+1 then the PWM output value is
 213 the one of trip point N. The automatic control mode is less flexible
 214 than the manual control mode, but it reacts faster, is more robust and
 215 doesn't use CPU cycles.
 216
 217 Trip points must be set properly before switching to automatic fan speed
 218 control mode. The driver will perform basic integrity checks before
 219 actually switching to automatic control mode.
 220
 221
 222 Temperature offset attributes
 223 -----------------------------
 224
 225 The driver supports temp[1-3]_offset sysfs attributes to adjust the reported
 226 temperature for thermal diodes or diode-connected thermal transistors.
 227 If a temperature sensor is configured for thermistors, the attribute values
 228 are ignored. If the thermal sensor type is Intel PECI, the temperature offset
 229 must be programmed to the critical CPU temperature.