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 > + > +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 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 > +pwm#_auto_point2_temp. > + > +Notes > +----- > + > +As stated above, the temperature inputs must be read periodically from > +userspace in order for the automatic pwm algorithm to run. Applied, thanks. -- Jean Delvare
