[lm-sensors] [PATCH v2] adt7470: Add documentation
khali at linux-fr.org
Thu Oct 9 12:07:40 CEST 2008
On Wed, 8 Oct 2008 12:00:48 -0700, Darrick J. Wong wrote:
> Add at least the bare minimum of documentation for this chip.
> Signed-off-by: Darrick J. Wong <djwong at us.ibm.com>
> Documentation/hwmon/adt7470 | 76 +++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 76 insertions(+), 0 deletions(-)
> diff --git a/Documentation/hwmon/adt7470 b/Documentation/hwmon/adt7470
> new file mode 100644
> index 0000000..109650a
> --- /dev/null
> +++ b/Documentation/hwmon/adt7470
> @@ -0,0 +1,76 @@
> +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
> +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 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 DOES NOT sample all inputs continuously. A single pin on the
> +ADT7470 is connected to a multitude of thermal diodes, but the chip must be
> +instructed explicitly to read the multitude of diodes. If you want to use
> +automatic fan control mode, you must manually read any of the temperature
> +sensors or the fan control algorithm will not run. The chip WILL NOT DO THIS
> +AUTOMATICALLY; this must be done from userspace. This may be a bug in the chip
> +design, given that many other AD chips take care of this. 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
> +As stated above, the temperature inputs must be read periodically from
> +userspace in order for the automatic pwm algorithm to run.
More information about the lm-sensors