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