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hwmon: (nct6775) Add support for temperature sensors
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1Note
2====
3
4This driver supersedes the NCT6775F and NCT6776F support in the W83627EHF
5driver.
6
7Kernel driver NCT6775
8=====================
9
10Supported chips:
11 * Nuvoton NCT6775F/W83667HG-I
12 Prefix: 'nct6775'
13 Addresses scanned: ISA address retrieved from Super I/O registers
14 Datasheet: Available from Nuvoton upon request
15 * Nuvoton NCT6776F
16 Prefix: 'nct6776'
17 Addresses scanned: ISA address retrieved from Super I/O registers
18 Datasheet: Available from Nuvoton upon request
19 * Nuvoton NCT6779D
20 Prefix: 'nct6779'
21 Addresses scanned: ISA address retrieved from Super I/O registers
22 Datasheet: Available from Nuvoton upon request
23
24Authors:
25 Guenter Roeck <linux@roeck-us.net>
26
27Description
28-----------
29
30This driver implements support for the Nuvoton NCT6775F, NCT6776F, and NCT6779D
31super I/O chips.
32
33The chips support up to 25 temperature monitoring sources. Up to 6 of those are
34direct temperature sensor inputs, the others are special sources such as PECI,
35PCH, and SMBUS. Depending on the chip type, 2 to 6 of the temperature sources
36can be monitored and compared against minimum, maximum, and critical
37temperatures. The driver reports up to 10 of the temperatures to the user.
38There are 4 to 5 fan rotation speed sensors, 8 to 15 analog voltage sensors,
39one VID, alarms with beep warnings (control unimplemented), and some automatic
40fan regulation strategies (plus manual fan control mode).
41
42The temperature sensor sources on all chips are configurable. The configured
43source for each of the temperature sensors is provided in tempX_label.
44
45Temperatures are measured in degrees Celsius and measurement resolution is
46either 1 degC or 0.5 degC, depending on the temperature source and
47configuration. An alarm is triggered when the temperature gets higher than
48the high limit; it stays on until the temperature falls below the hysteresis
49value. Alarms are only supported for temp1 to temp6, depending on the chip type.
50
51Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
52triggered if the rotation speed has dropped below a programmable limit. On
53NCT6775F, fan readings can be divided by a programmable divider (1, 2, 4, 8,
5416, 32, 64 or 128) to give the readings more range or accuracy; the other chips
55do not have a fan speed divider. The driver sets the most suitable fan divisor
56itself; specifically, it doubles the divider value each time a fan speed reading
57returns an invalid value. Some fans might not be present because they share pins
58with other functions.
59
60Voltage sensors (also known as IN sensors) report their values in millivolts.
61An alarm is triggered if the voltage has crossed a programmable minimum
62or maximum limit.
63
64The driver supports automatic fan control mode known as Thermal Cruise.
65In this mode, the chip attempts to keep the measured temperature in a
66predefined temperature range. If the temperature goes out of range, fan
67is driven slower/faster to reach the predefined range again.
68
69The mode works for fan1-fan5.
70
71Usage Notes
72-----------
73
74On various ASUS boards with NCT6776F, it appears that CPUTIN is not really
75connected to anything and floats, or that it is connected to some non-standard
76temperature measurement device. As a result, the temperature reported on CPUTIN
77will not reflect a usable value. It often reports unreasonably high
78temperatures, and in some cases the reported temperature declines if the actual
79temperature increases (similar to the raw PECI temperature value - see PECI
80specification for details). CPUTIN should therefore be be ignored on ASUS
81boards. The CPU temperature on ASUS boards is reported from PECI 0.