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New documentation for the adt7475 driver, based on the adt7473 driver documentation. It is IMHO much more useful that the previous documentation which was essentially redundant with sysfs-interface. Signed-off-by: Jean Delvare <khali@linux-fr.org> Cc: "Mark M. Hoffman" <mhoffman@lightlink.com> Cc: Hans de Goede <hdegoede@redhat.com> Cc: Jordan Crouse <jordan@cosmicpenguin.net> Cc: "Darrick J. Wong" <djwong@us.ibm.com>
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| This describes the interface for the ADT7475 driver: | ||
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| (there are 4 fans, numbered fan1 to fan4): | ||
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| fanX_input Read the current speed of the fan (in RPMs) | ||
| fanX_min Read/write the minimum speed of the fan. Dropping | ||
| below this sets an alarm. | ||
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| (there are three PWMs, numbered pwm1 to pwm3): | ||
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| pwmX Read/write the current duty cycle of the PWM. Writes | ||
| only have effect when auto mode is turned off (see | ||
| below). Range is 0 - 255. | ||
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| pwmX_enable Fan speed control method: | ||
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| 0 - No control (fan at full speed) | ||
| 1 - Manual fan speed control (using pwm[1-*]) | ||
| 2 - Automatic fan speed control | ||
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| pwmX_auto_channels_temp Select which channels affect this PWM | ||
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| 1 - TEMP1 controls PWM | ||
| 2 - TEMP2 controls PWM | ||
| 4 - TEMP3 controls PWM | ||
| 6 - TEMP2 and TEMP3 control PWM | ||
| 7 - All three inputs control PWM | ||
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| pwmX_freq Read/write the PWM frequency in Hz. The number | ||
| should be one of the following: | ||
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| 11 Hz | ||
| 14 Hz | ||
| 22 Hz | ||
| 29 Hz | ||
| 35 Hz | ||
| 44 Hz | ||
| 58 Hz | ||
| 88 Hz | ||
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| pwmX_auto_point1_pwm Read/write the minimum PWM duty cycle in automatic mode | ||
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| pwmX_auto_point2_pwm Read/write the maximum PWM duty cycle in automatic mode | ||
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| (there are three temperature settings numbered temp1 to temp3): | ||
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| tempX_input Read the current temperature. The value is in milli | ||
| degrees of Celsius. | ||
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| tempX_max Read/write the upper temperature limit - exceeding this | ||
| will cause an alarm. | ||
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| tempX_min Read/write the lower temperature limit - exceeding this | ||
| will cause an alarm. | ||
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| tempX_offset Read/write the temperature adjustment offset | ||
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| tempX_crit Read/write the THERM limit for remote1. | ||
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| tempX_crit_hyst Set the temperature value below crit where the | ||
| fans will stay on - this helps drive the temperature | ||
| low enough so it doesn't stay near the edge and | ||
| cause THERM to keep tripping. | ||
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| tempX_auto_point1_temp Read/write the minimum temperature where the fans will | ||
| turn on in automatic mode. | ||
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| tempX_auto_point2_temp Read/write the maximum temperature over which the fans | ||
| will run in automatic mode. tempX_auto_point1_temp | ||
| and tempX_auto_point2_temp together define the | ||
| range of automatic control. | ||
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| tempX_alarm Read a 1 if the max/min alarm is set | ||
| tempX_fault Read a 1 if either temp1 or temp3 diode has a fault | ||
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| (There are two voltage settings, in1 and in2): | ||
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| inX_input Read the current voltage on VCC. Value is in | ||
| millivolts. | ||
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| inX_min read/write the minimum voltage limit. | ||
| Dropping below this causes an alarm. | ||
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| inX_max read/write the maximum voltage limit. | ||
| Exceeding this causes an alarm. | ||
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| inX_alarm Read a 1 if the max/min alarm is set. | ||
| Kernel driver adt7475 | ||
| ===================== | ||
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| 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 | ||
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| Authors: | ||
| Jordan Crouse | ||
| Hans de Goede | ||
| Darrick J. Wong (documentation) | ||
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| Description | ||
| ----------- | ||
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| This driver implements support for the Analog Devices ADT7473 and ADT7475 | ||
| chip family. Both chips differ only in minor details. They will be | ||
| collectively designed by the name "ADT747x" in the rest of this document. | ||
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| 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) 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. | ||
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| 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. | ||
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| 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. | ||
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| 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. | ||
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| Special Features | ||
| ---------------- | ||
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| 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. | ||
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| The datasheet is very detailed and describes a procedure for determining | ||
| an optimal configuration for the automatic PWM control. | ||
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| Fan Speed Control | ||
| ----------------- | ||
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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 | ||
| 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 | ||
| 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). | ||
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| Fan speed may be set to maximum when the temperature sensor associated with | ||
| the PWM control exceeds temp#_max. | ||
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| Notes | ||
| ----- | ||
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| 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. |