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diff --git a/Documentation/hwmon/adt7475.rst b/Documentation/hwmon/adt7475.rst new file mode 100644 index 000000000000..ef3ea1ea9bc1 --- /dev/null +++ b/Documentation/hwmon/adt7475.rst @@ -0,0 +1,156 @@ +Kernel driver adt7475 +===================== + +Supported chips: + + * Analog Devices ADT7473 + + Prefix: 'adt7473' + + Addresses scanned: I2C 0x2C, 0x2D, 0x2E + + Datasheet: Publicly available at the On Semiconductors website + + * Analog Devices ADT7475 + + Prefix: 'adt7475' + + Addresses scanned: I2C 0x2E + + Datasheet: Publicly available at the On Semiconductors website + + * Analog Devices ADT7476 + + Prefix: 'adt7476' + + Addresses scanned: I2C 0x2C, 0x2D, 0x2E + + Datasheet: Publicly available at the On Semiconductors website + + * Analog Devices ADT7490 + + Prefix: 'adt7490' + + Addresses scanned: I2C 0x2C, 0x2D, 0x2E + + Datasheet: Publicly available at the On Semiconductors website + +Authors: + - Jordan Crouse + - Hans de Goede + - Darrick J. Wong (documentation) + - Jean Delvare + + +Description +----------- + +This driver implements support for the Analog Devices ADT7473, ADT7475, +ADT7476 and ADT7490 chip family. The ADT7473 and ADT7475 differ only in +minor details. The ADT7476 has additional features, including extra voltage +measurement inputs and VID support. The ADT7490 also has additional +features, including extra voltage measurement inputs and PECI support. All +the supported chips will be collectively designed by the name "ADT747x" in +the rest of this document. + +The ADT747x uses the 2-wire interface compatible with the SMBus 2.0 +specification. Using an analog to digital converter it measures three (3) +temperatures and two (2) or more voltages. It has four (4) 16-bit counters +for measuring fan speed. There are three (3) PWM outputs that can be used +to control fan speed. + +A sophisticated control system for the PWM outputs is designed into the +ADT747x that allows fan speed to be adjusted automatically based on any of the +three temperature sensors. Each PWM output is individually adjustable and +programmable. Once configured, the ADT747x will adjust the PWM outputs in +response to the measured temperatures without further host intervention. +This feature can also be disabled for manual control of the PWM's. + +Each of the measured inputs (voltage, temperature, fan speed) has +corresponding high/low limit values. The ADT747x will signal an ALARM if +any measured value exceeds either limit. + +The ADT747x samples all inputs continuously. The driver will not read +the registers more often than once every other second. Further, +configuration data is only read once per minute. + +Chip Differences Summary +------------------------ + +ADT7473: + * 2 voltage inputs + * system acoustics optimizations (not implemented) + +ADT7475: + * 2 voltage inputs + +ADT7476: + * 5 voltage inputs + * VID support + +ADT7490: + * 6 voltage inputs + * 1 Imon input (not implemented) + * PECI support (not implemented) + * 2 GPIO pins (not implemented) + * system acoustics optimizations (not implemented) + +Sysfs Mapping +------------- + +==== =========== =========== ========= ========== +in ADT7490 ADT7476 ADT7475 ADT7473 +==== =========== =========== ========= ========== +in0 2.5VIN (22) 2.5VIN (22) - - +in1 VCCP (23) VCCP (23) VCCP (14) VCCP (14) +in2 VCC (4) VCC (4) VCC (4) VCC (3) +in3 5VIN (20) 5VIN (20) +in4 12VIN (21) 12VIN (21) +in5 VTT (8) +==== =========== =========== ========= ========== + +Special Features +---------------- + +The ADT747x has a 10-bit ADC and can therefore measure temperatures +with a resolution of 0.25 degree Celsius. Temperature readings can be +configured either for two's complement format or "Offset 64" format, +wherein 64 is subtracted from the raw value to get the temperature value. + +The datasheet is very detailed and describes a procedure for determining +an optimal configuration for the automatic PWM control. + +Fan Speed Control +----------------- + +The driver exposes two trip points per PWM channel. + +- point1: Set the PWM speed at the lower temperature bound +- point2: Set the PWM speed at the higher temperature bound + +The ADT747x will scale the PWM linearly between the lower and higher PWM +speed when the temperature is between the two temperature boundaries. +Temperature boundaries are associated to temperature channels rather than +PWM outputs, and a given PWM output can be controlled by several temperature +channels. As a result, the ADT747x may compute more than one PWM value +for a channel at a given time, in which case the maximum value (fastest +fan speed) is applied. PWM values range from 0 (off) to 255 (full speed). + +Fan speed may be set to maximum when the temperature sensor associated with +the PWM control exceeds temp#_max. + +At Tmin - hysteresis the PWM output can either be off (0% duty cycle) or at the +minimum (i.e. auto_point1_pwm). This behaviour can be configured using the +`pwm[1-*]_stall_disable sysfs attribute`. A value of 0 means the fans will shut +off. A value of 1 means the fans will run at auto_point1_pwm. + +The responsiveness of the ADT747x to temperature changes can be configured. +This allows smoothing of the fan speed transition. To set the transition time +set the value in ms in the `temp[1-*]_smoothing` sysfs attribute. + +Notes +----- + +The nVidia binary driver presents an ADT7473 chip via an on-card i2c bus. +Unfortunately, they fail to set the i2c adapter class, so this driver may +fail to find the chip until the nvidia driver is patched. |