via686a.rst (3530B)
1Kernel driver via686a 2===================== 3 4Supported chips: 5 6 * Via VT82C686A, VT82C686B Southbridge Integrated Hardware Monitor 7 8 Prefix: 'via686a' 9 10 Addresses scanned: ISA in PCI-space encoded address 11 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 by 19 - Jonathan Teh Soon Yew <j.teh@iname.com> 20 - and Alex van Kaam <darkside@chello.nl>.) 21 22Module Parameters 23----------------- 24 25======================= ======================================================= 26force_addr=0xaddr Set the I/O base address. Useful for boards that 27 don't set the address in the BIOS. Look for a BIOS 28 upgrade before resorting to this. Does not do a 29 PCI force; the via686a must still be present in lspci. 30 Don't use this unless the driver complains that the 31 base address is not set. 32 Example: 'modprobe via686a force_addr=0x6000' 33======================= ======================================================= 34 35Description 36----------- 37 38The driver does not distinguish between the chips and reports 39all 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 speed 46sensors, five voltage sensors and alarms. 47 48Temperatures are measured in degrees Celsius. An alarm is triggered once 49when the Overtemperature Shutdown limit is crossed; it is triggered again 50as soon as it drops below the hysteresis value. 51 52Fan rotation speeds are reported in RPM (rotations per minute). An alarm is 53triggered if the rotation speed has dropped below a programmable limit. Fan 54readings can be divided by a programmable divider (1, 2, 4 or 8) to give 55the readings more range or accuracy. Not all RPM values can accurately be 56represented, so some rounding is done. With a divider of 2, the lowest 57representable 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 minimum 61or maximum limit. Voltages are internally scalled, so each voltage channel 62has a different resolution and range. 63 64If an alarm triggers, it will remain triggered until the hardware register 65is read at least once. This means that the cause for the alarm may 66already have disappeared! Note that in the current implementation, all 67hardware registers are read whenever any data is read (unless it is less 68than 1.5 seconds since the last update). This means that you can easily 69miss once-only alarms. 70 71The driver only updates its values each 1.5 seconds; reading it more often 72will do no harm, but will return 'old' values. 73 74Known Issues 75------------ 76 77This driver handles sensors integrated in some VIA south bridges. It is 78possible that a motherboard maker used a VT82C686A/B chip as part of a 79product design but was not interested in its hardware monitoring features, 80in which case the sensor inputs will not be wired. This is the case of 81the 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 which 83don't seem to make any sense, don't look any further: your chip is simply 84not wired for hardware monitoring.