mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-23 12:43:55 +08:00
7ebd8b66dd
Now that all files were converted to ReST format, rename them and add an index. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
95 lines
2.9 KiB
ReStructuredText
95 lines
2.9 KiB
ReStructuredText
Kernel driver adt7470
|
|
=====================
|
|
|
|
Supported chips:
|
|
|
|
* Analog Devices ADT7470
|
|
|
|
Prefix: 'adt7470'
|
|
|
|
Addresses scanned: I2C 0x2C, 0x2E, 0x2F
|
|
|
|
Datasheet: Publicly available at the Analog Devices website
|
|
|
|
Author: Darrick J. Wong
|
|
|
|
Description
|
|
-----------
|
|
|
|
This driver implements support for the Analog Devices ADT7470 chip. There may
|
|
be other chips that implement this interface.
|
|
|
|
The ADT7470 uses the 2-wire interface compatible with the SMBus 2.0
|
|
specification. Using an analog to digital converter it measures up to ten (10)
|
|
external temperatures. It has four (4) 16-bit counters for measuring fan speed.
|
|
There are four (4) PWM outputs that can be used to control fan speed.
|
|
|
|
A sophisticated control system for the PWM outputs is designed into the ADT7470
|
|
that allows fan speed to be adjusted automatically based on any of the ten
|
|
temperature sensors. Each PWM output is individually adjustable and
|
|
programmable. Once configured, the ADT7470 will adjust the PWM outputs in
|
|
response to the measured temperatures with further host intervention. This
|
|
feature can also be disabled for manual control of the PWM's.
|
|
|
|
Each of the measured inputs (temperature, fan speed) has corresponding high/low
|
|
limit values. The ADT7470 will signal an ALARM if any measured value exceeds
|
|
either limit.
|
|
|
|
The ADT7470 samples all inputs continuously. A kernel thread is started up for
|
|
the purpose of periodically querying the temperature sensors, thus allowing the
|
|
automatic fan pwm control to set the fan speed. The driver will not read the
|
|
registers more often than once every 5 seconds. Further, configuration data is
|
|
only read once per minute.
|
|
|
|
Special Features
|
|
----------------
|
|
|
|
The ADT7470 has a 8-bit ADC and is capable of measuring temperatures with 1
|
|
degC resolution.
|
|
|
|
The Analog Devices datasheet is very detailed and describes a procedure for
|
|
determining an optimal configuration for the automatic PWM control.
|
|
|
|
Configuration Notes
|
|
-------------------
|
|
|
|
Besides standard interfaces driver adds the following:
|
|
|
|
* PWM Control
|
|
|
|
* pwm#_auto_point1_pwm and pwm#_auto_point1_temp and
|
|
* pwm#_auto_point2_pwm and pwm#_auto_point2_temp -
|
|
|
|
- point1: Set the pwm speed at a lower temperature bound.
|
|
- point2: Set the pwm speed at a higher temperature bound.
|
|
|
|
The ADT7470 will scale the pwm between the lower and higher pwm speed when
|
|
the temperature is between the two temperature boundaries. PWM values range
|
|
from 0 (off) to 255 (full speed). Fan speed will be set to maximum when the
|
|
temperature sensor associated with the PWM control exceeds
|
|
pwm#_auto_point2_temp.
|
|
|
|
The driver also allows control of the PWM frequency:
|
|
|
|
* pwm1_freq
|
|
|
|
The PWM frequency is rounded to the nearest one of:
|
|
|
|
* 11.0 Hz
|
|
* 14.7 Hz
|
|
* 22.1 Hz
|
|
* 29.4 Hz
|
|
* 35.3 Hz
|
|
* 44.1 Hz
|
|
* 58.8 Hz
|
|
* 88.2 Hz
|
|
* 1.4 kHz
|
|
* 22.5 kHz
|
|
|
|
Notes
|
|
-----
|
|
|
|
The temperature inputs no longer need to be read periodically from userspace in
|
|
order for the automatic pwm algorithm to run. This was the case for earlier
|
|
versions of the driver.
|