mirror of
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2025-09-04 20:19:47 +08:00
6722feada7
We've never seen any device supported by the lm78 or w83781d driver at addresses 0x20-0x27, so let's stop probing these addresses. Extra probes cost time, and have potential for confusing or misdetecting other I2C devices. Signed-off-by: Jean Delvare <khali@linux-fr.org> Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com>
68 lines
3.1 KiB
Plaintext
68 lines
3.1 KiB
Plaintext
Kernel driver lm78
|
|
==================
|
|
|
|
Supported chips:
|
|
* National Semiconductor LM78 / LM78-J
|
|
Prefix: 'lm78'
|
|
Addresses scanned: I2C 0x28 - 0x2f, ISA 0x290 (8 I/O ports)
|
|
Datasheet: Publicly available at the National Semiconductor website
|
|
http://www.national.com/
|
|
* National Semiconductor LM79
|
|
Prefix: 'lm79'
|
|
Addresses scanned: I2C 0x28 - 0x2f, ISA 0x290 (8 I/O ports)
|
|
Datasheet: Publicly available at the National Semiconductor website
|
|
http://www.national.com/
|
|
|
|
Author: Frodo Looijaard <frodol@dds.nl>
|
|
|
|
Description
|
|
-----------
|
|
|
|
This driver implements support for the National Semiconductor LM78, LM78-J
|
|
and LM79. They are described as 'Microprocessor System Hardware Monitors'.
|
|
|
|
There is almost no difference between the three supported chips. Functionally,
|
|
the LM78 and LM78-J are exactly identical. The LM79 has one more VID line,
|
|
which is used to report the lower voltages newer Pentium processors use.
|
|
From here on, LM7* means either of these three types.
|
|
|
|
The LM7* implements one temperature sensor, three fan rotation speed sensors,
|
|
seven voltage sensors, VID lines, alarms, and some miscellaneous stuff.
|
|
|
|
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. A more useful behavior
|
|
can be found by setting the Hysteresis value to +127 degrees Celsius; in
|
|
this case, alarms are issued during all the time when the actual temperature
|
|
is above the Overtemperature Shutdown value. Measurements are guaranteed
|
|
between -55 and +125 degrees, with a resolution of 1 degree.
|
|
|
|
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. Note that minimum in this case always means 'closest to
|
|
zero'; this is important for negative voltage measurements. All voltage
|
|
inputs can measure voltages between 0 and 4.08 volts, with a resolution
|
|
of 0.016 volt.
|
|
|
|
The VID lines encode the core voltage value: the voltage level your processor
|
|
should work with. This is hardcoded by the mainboard and/or processor itself.
|
|
It is a value in volts. When it is unconnected, you will often find the
|
|
value 3.50 V here.
|
|
|
|
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 LM7* only updates its values each 1.5 seconds; reading it more often
|
|
will do no harm, but will return 'old' values.
|