ccf988b66d
Convert each file at I2C subsystem, renaming them to .rst and adding to the driver-api book. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Acked-by: Wolfram Sang <wsa@the-dreams.de> Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
85 lines
3.4 KiB
ReStructuredText
85 lines
3.4 KiB
ReStructuredText
Kernel driver via686a
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=====================
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Supported chips:
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* Via VT82C686A, VT82C686B Southbridge Integrated Hardware Monitor
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Prefix: 'via686a'
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Addresses scanned: ISA in PCI-space encoded address
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Datasheet: On request through web form (http://www.via.com.tw/en/resources/download-center/)
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Authors:
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- Kyösti Mälkki <kmalkki@cc.hut.fi>,
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- Mark D. Studebaker <mdsxyz123@yahoo.com>
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- Bob Dougherty <bobd@stanford.edu>
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- (Some conversion-factor data were contributed by
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- Jonathan Teh Soon Yew <j.teh@iname.com>
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- and Alex van Kaam <darkside@chello.nl>.)
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Module Parameters
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-----------------
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======================= =======================================================
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force_addr=0xaddr Set the I/O base address. Useful for boards that
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don't set the address in the BIOS. Look for a BIOS
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upgrade before resorting to this. Does not do a
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PCI force; the via686a must still be present in lspci.
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Don't use this unless the driver complains that the
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base address is not set.
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Example: 'modprobe via686a force_addr=0x6000'
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======================= =======================================================
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Description
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-----------
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The driver does not distinguish between the chips and reports
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all as a 686A.
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The Via 686a southbridge has integrated hardware monitor functionality.
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It also has an I2C bus, but this driver only supports the hardware monitor.
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For the I2C bus driver, see <file:Documentation/i2c/busses/i2c-viapro.rst>
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The Via 686a implements three temperature sensors, two fan rotation speed
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sensors, five voltage sensors and alarms.
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Temperatures are measured in degrees Celsius. An alarm is triggered once
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when the Overtemperature Shutdown limit is crossed; it is triggered again
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as soon as it drops below the hysteresis value.
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Fan rotation speeds are reported in RPM (rotations per minute). An alarm is
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triggered if the rotation speed has dropped below a programmable limit. Fan
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readings can be divided by a programmable divider (1, 2, 4 or 8) to give
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the readings more range or accuracy. Not all RPM values can accurately be
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represented, so some rounding is done. With a divider of 2, the lowest
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representable value is around 2600 RPM.
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Voltage sensors (also known as IN sensors) report their values in volts.
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An alarm is triggered if the voltage has crossed a programmable minimum
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or maximum limit. Voltages are internally scalled, so each voltage channel
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has a different resolution and range.
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If an alarm triggers, it will remain triggered until the hardware register
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is read at least once. This means that the cause for the alarm may
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already have disappeared! Note that in the current implementation, all
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hardware registers are read whenever any data is read (unless it is less
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than 1.5 seconds since the last update). This means that you can easily
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miss once-only alarms.
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The driver only updates its values each 1.5 seconds; reading it more often
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will do no harm, but will return 'old' values.
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Known Issues
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------------
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This driver handles sensors integrated in some VIA south bridges. It is
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possible that a motherboard maker used a VT82C686A/B chip as part of a
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product design but was not interested in its hardware monitoring features,
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in which case the sensor inputs will not be wired. This is the case of
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the Asus K7V, A7V and A7V133 motherboards, to name only a few of them.
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So, if you need the force_addr parameter, and end up with values which
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don't seem to make any sense, don't look any further: your chip is simply
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not wired for hardware monitoring.
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