Root/Documentation/hwmon/it87

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  * SiS950 [clone of IT8705F]
30    Prefix: 'it87'
31    Addresses scanned: from Super I/O config space (8 I/O ports)
32    Datasheet: No longer be available
33
34Authors:
35    Christophe Gauthron
36    Jean Delvare <khali@linux-fr.org>
37
38
39Module Parameters
40-----------------
41
42* update_vbat: int
43
44  0 if vbat should report power on value, 1 if vbat should be updated after
45  each read. Default is 0. On some boards the battery voltage is provided
46  by either the battery or the onboard power supply. Only the first reading
47  at power on will be the actual battery voltage (which the chip does
48  automatically). On other boards the battery voltage is always fed to
49  the chip so can be read at any time. Excessive reading may decrease
50  battery life but no information is given in the datasheet.
51
52* fix_pwm_polarity int
53
54  Force PWM polarity to active high (DANGEROUS). Some chips are
55  misconfigured by BIOS - PWM values would be inverted. This option tries
56  to fix this. Please contact your BIOS manufacturer and ask him for fix.
57
58
59Hardware Interfaces
60-------------------
61
62All the chips suported by this driver are LPC Super-I/O chips, accessed
63through the LPC bus (ISA-like I/O ports). The IT8712F additionally has an
64SMBus interface to the hardware monitoring functions. This driver no
65longer supports this interface though, as it is slower and less reliable
66than the ISA access, and was only available on a small number of
67motherboard models.
68
69
70Description
71-----------
72
73This driver implements support for the IT8705F, IT8712F, IT8716F,
74IT8718F, IT8720F, IT8721F, IT8726F, IT8758E and SiS950 chips.
75
76These chips are 'Super I/O chips', supporting floppy disks, infrared ports,
77joysticks and other miscellaneous stuff. For hardware monitoring, they
78include an 'environment controller' with 3 temperature sensors, 3 fan
79rotation speed sensors, 8 voltage sensors, and associated alarms.
80
81The IT8712F and IT8716F additionally feature VID inputs, used to report
82the Vcore voltage of the processor. The early IT8712F have 5 VID pins,
83the IT8716F and late IT8712F have 6. They are shared with other functions
84though, so the functionality may not be available on a given system.
85
86The IT8718F and IT8720F also features VID inputs (up to 8 pins) but the value
87is stored in the Super-I/O configuration space. Due to technical limitations,
88this value can currently only be read once at initialization time, so
89the driver won't notice and report changes in the VID value. The two
90upper VID bits share their pins with voltage inputs (in5 and in6) so you
91can't have both on a given board.
92
93The IT8716F, IT8718F, IT8720F, IT8721F/IT8758E and later IT8712F revisions
94have support for 2 additional fans. The additional fans are supported by the
95driver.
96
97The IT8716F, IT8718F, IT8720F and IT8721F/IT8758E, and late IT8712F and
98IT8705F also have optional 16-bit tachometer counters for fans 1 to 3. This
99is better (no more fan clock divider mess) but not compatible with the older
100chips and revisions. The 16-bit tachometer mode is enabled by the driver when
101one of the above chips is detected.
102
103The IT8726F is just bit enhanced IT8716F with additional hardware
104for AMD power sequencing. Therefore the chip will appear as IT8716F
105to userspace applications.
106
107Temperatures are measured in degrees Celsius. An alarm is triggered once
108when the Overtemperature Shutdown limit is crossed.
109
110Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
111triggered if the rotation speed has dropped below a programmable limit. When
11216-bit tachometer counters aren't used, fan readings can be divided by
113a programmable divider (1, 2, 4 or 8) to give the readings more range or
114accuracy. With a divider of 2, the lowest representable value is around
1152600 RPM. Not all RPM values can accurately be represented, so some rounding
116is done.
117
118Voltage sensors (also known as IN sensors) report their values in volts. An
119alarm is triggered if the voltage has crossed a programmable minimum or
120maximum limit. Note that minimum in this case always means 'closest to
121zero'; this is important for negative voltage measurements. All voltage
122inputs can measure voltages between 0 and 4.08 volts, with a resolution of
1230.016 volt (except IT8721F/IT8758E: 0.012 volt.) The battery voltage in8 does
124not have limit registers.
125
126On the IT8721F/IT8758E, some voltage inputs are internal and scaled inside
127the chip (in7, in8 and optionally in3). The driver handles this transparently
128so user-space doesn't have to care.
129
130The VID lines (IT8712F/IT8716F/IT8718F/IT8720F) encode the core voltage value:
131the voltage level your processor should work with. This is hardcoded by
132the mainboard and/or processor itself. It is a value in volts.
133
134If an alarm triggers, it will remain triggered until the hardware register
135is read at least once. This means that the cause for the alarm may already
136have disappeared! Note that in the current implementation, all hardware
137registers are read whenever any data is read (unless it is less than 1.5
138seconds since the last update). This means that you can easily miss
139once-only alarms.
140
141Out-of-limit readings can also result in beeping, if the chip is properly
142wired and configured. Beeping can be enabled or disabled per sensor type
143(temperatures, voltages and fans.)
144
145The IT87xx only updates its values each 1.5 seconds; reading it more often
146will do no harm, but will return 'old' values.
147
148To change sensor N to a thermistor, 'echo 4 > tempN_type' where N is 1, 2,
149or 3. To change sensor N to a thermal diode, 'echo 3 > tempN_type'.
150Give 0 for unused sensor. Any other value is invalid. To configure this at
151startup, consult lm_sensors's /etc/sensors.conf. (4 = thermistor;
1523 = thermal diode)
153
154
155Fan speed control
156-----------------
157
158The fan speed control features are limited to manual PWM mode. Automatic
159"Smart Guardian" mode control handling is only implemented for older chips
160(see below.) However if you want to go for "manual mode" just write 1 to
161pwmN_enable.
162
163If you are only able to control the fan speed with very small PWM values,
164try lowering the PWM base frequency (pwm1_freq). Depending on the fan,
165it may give you a somewhat greater control range. The same frequency is
166used to drive all fan outputs, which is why pwm2_freq and pwm3_freq are
167read-only.
168
169
170Automatic fan speed control (old interface)
171-------------------------------------------
172
173The driver supports the old interface to automatic fan speed control
174which is implemented by IT8705F chips up to revision F and IT8712F
175chips up to revision G.
176
177This interface implements 4 temperature vs. PWM output trip points.
178The PWM output of trip point 4 is always the maximum value (fan running
179at full speed) while the PWM output of the other 3 trip points can be
180freely chosen. The temperature of all 4 trip points can be freely chosen.
181Additionally, trip point 1 has an hysteresis temperature attached, to
182prevent fast switching between fan on and off.
183
184The chip automatically computes the PWM output value based on the input
185temperature, based on this simple rule: if the temperature value is
186between trip point N and trip point N+1 then the PWM output value is
187the one of trip point N. The automatic control mode is less flexible
188than the manual control mode, but it reacts faster, is more robust and
189doesn't use CPU cycles.
190
191Trip points must be set properly before switching to automatic fan speed
192control mode. The driver will perform basic integrity checks before
193actually switching to automatic control mode.
194

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