[PATCH] hwmon: Add f71805f documentation

Kernel driver f71805f

=====================

Supported chips:

  * Fintek F71805F/FG

    Prefix: 'f71805f'

    Addresses scanned: none, address read from Super I/O config space

    Datasheet: Provided by Fintek on request

Author: Jean Delvare <khali@linux-fr.org>

Thanks to Denis Kieft from Barracuda Networks for the donation of a

test system (custom Jetway K8M8MS motherboard, with CPU and RAM) and

for providing initial documentation.

Thanks to Kris Chen from Fintek for answering technical questions and

providing additional documentation.

Thanks to Chris Lin from Jetway for providing wiring schematics and

anwsering technical questions.

Description

-----------

The Fintek F71805F/FG Super I/O chip includes complete hardware monitoring

capabilities. It can monitor up to 9 voltages (counting its own power

source), 3 fans and 3 temperature sensors.

This chip also has fan controlling features, using either DC or PWM, in

three different modes (one manual, two automatic). The driver doesn't

support these features yet.

The driver assumes that no more than one chip is present, which seems

reasonable.

Voltage Monitoring

------------------

Voltages are sampled by an 8-bit ADC with a LSB of 8 mV. The supported

range is thus from 0 to 2.040 V. Voltage values outside of this range

need external resistors. An exception is in0, which is used to monitor

the chip's own power source (+3.3V), and is divided internally by a

factor 2.

The two LSB of the voltage limit registers are not used (always 0), so

you can only set the limits in steps of 32 mV (before scaling).

The wirings and resistor values suggested by Fintek are as follow:

        pin                                           expected

        name    use           R1      R2     divider  raw val.

in0     VCC     VCC3.3V     int.    int.        2.00    1.65 V

in1     VIN1    VTT1.2V      10K       -        1.00    1.20 V

in2     VIN2    VRAM        100K    100K        2.00   ~1.25 V (1)

in3     VIN3    VCHIPSET     47K    100K        1.47    2.24 V (2)

in4     VIN4    VCC5V       200K     47K        5.25    0.95 V

in5     VIN5    +12V        200K     20K       11.00    1.05 V

in6     VIN6    VCC1.5V      10K       -        1.00    1.50 V

in7     VIN7    VCORE        10K       -        1.00   ~1.40 V (1)

in8     VIN8    VSB5V       200K     47K        1.00    0.95 V

(1) Depends on your hardware setup.

(2) Obviously not correct, swapping R1 and R2 would make more sense.

These values can be used as hints at best, as motherboard manufacturers

are free to use a completely different setup. As a matter of fact, the

Jetway K8M8MS uses a significantly different setup. You will have to

find out documentation about your own motherboard, and edit sensors.conf

accordingly.

Each voltage measured has associated low and high limits, each of which

triggers an alarm when crossed.

Fan Monitoring

--------------

Fan rotation speeds are reported as 12-bit values from a gated clock

signal. Speeds down to 366 RPM can be measured. There is no theoretical

high limit, but values over 6000 RPM seem to cause problem. The effective

resolution is much lower than you would expect, the step between different

register values being 10 rather than 1.

The chip assumes 2 pulse-per-revolution fans.

An alarm is triggered if the rotation speed drops below a programmable

limit or is too low to be measured.

Temperature Monitoring

----------------------

Temperatures are reported in degrees Celsius. Each temperature measured

has a high limit, those crossing triggers an alarm. There is an associated

hysteresis value, below which the temperature has to drop before the

alarm is cleared.

All temperature channels are external, there is no embedded temperature

sensor. Each channel can be used for connecting either a thermal diode

or a thermistor. The driver reports the currently selected mode, but

doesn't allow changing it. In theory, the BIOS should have configured

everything properly.