mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-27 14:43:58 +08:00
ede7fbdf52
Part 3: Move the drivers documentation, plus two general documentation files. Note that the patch "adds trailing whitespace", because it does move the files as-is, and some files happen to have trailing whitespace. Signed-off-by: Jean Delvare <khali@linux-fr.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
58 lines
2.2 KiB
Plaintext
58 lines
2.2 KiB
Plaintext
Kernel driver lm63
|
|
==================
|
|
|
|
Supported chips:
|
|
* National Semiconductor LM63
|
|
Prefix: 'lm63'
|
|
Addresses scanned: I2C 0x4c
|
|
Datasheet: Publicly available at the National Semiconductor website
|
|
http://www.national.com/pf/LM/LM63.html
|
|
|
|
Author: Jean Delvare <khali@linux-fr.org>
|
|
|
|
Thanks go to Tyan and especially Alex Buckingham for setting up a remote
|
|
access to their S4882 test platform for this driver.
|
|
http://www.tyan.com/
|
|
|
|
Description
|
|
-----------
|
|
|
|
The LM63 is a digital temperature sensor with integrated fan monitoring
|
|
and control.
|
|
|
|
The LM63 is basically an LM86 with fan speed monitoring and control
|
|
capabilities added. It misses some of the LM86 features though:
|
|
- No low limit for local temperature.
|
|
- No critical limit for local temperature.
|
|
- Critical limit for remote temperature can be changed only once. We
|
|
will consider that the critical limit is read-only.
|
|
|
|
The datasheet isn't very clear about what the tachometer reading is.
|
|
|
|
An explanation from National Semiconductor: The two lower bits of the read
|
|
value have to be masked out. The value is still 16 bit in width.
|
|
|
|
All temperature values are given in degrees Celsius. Resolution is 1.0
|
|
degree for the local temperature, 0.125 degree for the remote temperature.
|
|
|
|
The fan speed is measured using a tachometer. Contrary to most chips which
|
|
store the value in an 8-bit register and have a selectable clock divider
|
|
to make sure that the result will fit in the register, the LM63 uses 16-bit
|
|
value for measuring the speed of the fan. It can measure fan speeds down to
|
|
83 RPM, at least in theory.
|
|
|
|
Note that the pin used for fan monitoring is shared with an alert out
|
|
function. Depending on how the board designer wanted to use the chip, fan
|
|
speed monitoring will or will not be possible. The proper chip configuration
|
|
is left to the BIOS, and the driver will blindly trust it.
|
|
|
|
A PWM output can be used to control the speed of the fan. The LM63 has two
|
|
PWM modes: manual and automatic. Automatic mode is not fully implemented yet
|
|
(you cannot define your custom PWM/temperature curve), and mode change isn't
|
|
supported either.
|
|
|
|
The lm63 driver will not update its values more frequently than every
|
|
second; reading them more often will do no harm, but will return 'old'
|
|
values.
|
|
|