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1Kernel driver via686a2=====================3 4Supported chips:5 6 * Via VT82C686A, VT82C686B Southbridge Integrated Hardware Monitor7 8 Prefix: 'via686a'9 10 Addresses scanned: ISA in PCI-space encoded address11 12 Datasheet: On request through web form (http://www.via.com.tw/en/resources/download-center/)13 14Authors:15 - Kyösti Mälkki <kmalkki@cc.hut.fi>,16 - Mark D. Studebaker <mdsxyz123@yahoo.com>17 - Bob Dougherty <bobd@stanford.edu>18 - (Some conversion-factor data were contributed by19 - Jonathan Teh Soon Yew <j.teh@iname.com>20 - and Alex van Kaam <darkside@chello.nl>.)21 22Module Parameters23-----------------24 25======================= =======================================================26force_addr=0xaddr Set the I/O base address. Useful for boards that27 don't set the address in the BIOS. Look for a BIOS28 upgrade before resorting to this. Does not do a29 PCI force; the via686a must still be present in lspci.30 Don't use this unless the driver complains that the31 base address is not set.32 Example: 'modprobe via686a force_addr=0x6000'33======================= =======================================================34 35Description36-----------37 38The driver does not distinguish between the chips and reports39all as a 686A.40 41The Via 686a southbridge has integrated hardware monitor functionality.42It also has an I2C bus, but this driver only supports the hardware monitor.43For the I2C bus driver, see <file:Documentation/i2c/busses/i2c-viapro.rst>44 45The Via 686a implements three temperature sensors, two fan rotation speed46sensors, five voltage sensors and alarms.47 48Temperatures are measured in degrees Celsius. An alarm is triggered once49when the Overtemperature Shutdown limit is crossed; it is triggered again50as soon as it drops below the hysteresis value.51 52Fan rotation speeds are reported in RPM (rotations per minute). An alarm is53triggered if the rotation speed has dropped below a programmable limit. Fan54readings can be divided by a programmable divider (1, 2, 4 or 8) to give55the readings more range or accuracy. Not all RPM values can accurately be56represented, so some rounding is done. With a divider of 2, the lowest57representable value is around 2600 RPM.58 59Voltage sensors (also known as IN sensors) report their values in volts.60An alarm is triggered if the voltage has crossed a programmable minimum61or maximum limit. Voltages are internally scaled, so each voltage channel62has a different resolution and range.63 64If an alarm triggers, it will remain triggered until the hardware register65is read at least once. This means that the cause for the alarm may66already have disappeared! Note that in the current implementation, all67hardware registers are read whenever any data is read (unless it is less68than 1.5 seconds since the last update). This means that you can easily69miss once-only alarms.70 71The driver only updates its values each 1.5 seconds; reading it more often72will do no harm, but will return 'old' values.73 74Known Issues75------------76 77This driver handles sensors integrated in some VIA south bridges. It is78possible that a motherboard maker used a VT82C686A/B chip as part of a79product design but was not interested in its hardware monitoring features,80in which case the sensor inputs will not be wired. This is the case of81the Asus K7V, A7V and A7V133 motherboards, to name only a few of them.82So, if you need the force_addr parameter, and end up with values which83don't seem to make any sense, don't look any further: your chip is simply84not wired for hardware monitoring.85