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- Kernel driver via686a
- =====================
- Supported chips:
- * Via VT82C686A, VT82C686B Southbridge Integrated Hardware Monitor
- Prefix: 'via686a'
- Addresses scanned: ISA in PCI-space encoded address
- Datasheet: On request through web form (http://www.via.com.tw/en/resources/download-center/)
- Authors:
- Kyösti Mälkki <kmalkki@cc.hut.fi>,
- Mark D. Studebaker <mdsxyz123@yahoo.com>
- Bob Dougherty <bobd@stanford.edu>
- (Some conversion-factor data were contributed by
- Jonathan Teh Soon Yew <j.teh@iname.com>
- and Alex van Kaam <darkside@chello.nl>.)
- Module Parameters
- -----------------
- force_addr=0xaddr Set the I/O base address. Useful for boards that
- don't set the address in the BIOS. Look for a BIOS
- upgrade before resorting to this. Does not do a
- PCI force; the via686a must still be present in lspci.
- Don't use this unless the driver complains that the
- base address is not set.
- Example: 'modprobe via686a force_addr=0x6000'
- Description
- -----------
- The driver does not distinguish between the chips and reports
- all as a 686A.
- The Via 686a southbridge has integrated hardware monitor functionality.
- It also has an I2C bus, but this driver only supports the hardware monitor.
- For the I2C bus driver, see <file:Documentation/i2c/busses/i2c-viapro>
- The Via 686a implements three temperature sensors, two fan rotation speed
- sensors, five voltage sensors and alarms.
- Temperatures are measured in degrees Celsius. An alarm is triggered once
- when the Overtemperature Shutdown limit is crossed; it is triggered again
- as soon as it drops below the hysteresis value.
- Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
- triggered if the rotation speed has dropped below a programmable limit. Fan
- readings can be divided by a programmable divider (1, 2, 4 or 8) to give
- the readings more range or accuracy. Not all RPM values can accurately be
- represented, so some rounding is done. With a divider of 2, the lowest
- representable value is around 2600 RPM.
- Voltage sensors (also known as IN sensors) report their values in volts.
- An alarm is triggered if the voltage has crossed a programmable minimum
- or maximum limit. Voltages are internally scalled, so each voltage channel
- has a different resolution and range.
- If an alarm triggers, it will remain triggered until the hardware register
- is read at least once. This means that the cause for the alarm may
- already have disappeared! Note that in the current implementation, all
- hardware registers are read whenever any data is read (unless it is less
- than 1.5 seconds since the last update). This means that you can easily
- miss once-only alarms.
- The driver only updates its values each 1.5 seconds; reading it more often
- will do no harm, but will return 'old' values.
- Known Issues
- ------------
- This driver handles sensors integrated in some VIA south bridges. It is
- possible that a motherboard maker used a VT82C686A/B chip as part of a
- product design but was not interested in its hardware monitoring features,
- in which case the sensor inputs will not be wired. This is the case of
- the Asus K7V, A7V and A7V133 motherboards, to name only a few of them.
- So, if you need the force_addr parameter, and end up with values which
- don't seem to make any sense, don't look any further: your chip is simply
- not wired for hardware monitoring.
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