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Diffstat (limited to 'Documentation/hwmon/adt7475')
| -rw-r--r-- | Documentation/hwmon/adt7475 | 170 |
1 files changed, 83 insertions, 87 deletions
diff --git a/Documentation/hwmon/adt7475 b/Documentation/hwmon/adt7475 index a2b1abec850e..ebfee5524020 100644 --- a/Documentation/hwmon/adt7475 +++ b/Documentation/hwmon/adt7475 @@ -1,87 +1,83 @@ -This describes the interface for the ADT7475 driver: - -(there are 4 fans, numbered fan1 to fan4): - -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. - -(there are three PWMs, numbered pwm1 to pwm3): - -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. - -pwmX_enable Fan speed control method: - - 0 - No control (fan at full speed) - 1 - Manual fan speed control (using pwm[1-*]) - 2 - Automatic fan speed control - -pwmX_auto_channels_temp Select which channels affect this PWM - - 1 - TEMP1 controls PWM - 2 - TEMP2 controls PWM - 4 - TEMP3 controls PWM - 6 - TEMP2 and TEMP3 control PWM - 7 - All three inputs control PWM - -pwmX_freq Read/write the PWM frequency in Hz. The number - should be one of the following: - - 11 Hz - 14 Hz - 22 Hz - 29 Hz - 35 Hz - 44 Hz - 58 Hz - 88 Hz - -pwmX_auto_point1_pwm Read/write the minimum PWM duty cycle in automatic mode - -pwmX_auto_point2_pwm Read/write the maximum PWM duty cycle in automatic mode - -(there are three temperature settings numbered temp1 to temp3): - -tempX_input Read the current temperature. The value is in milli - degrees of Celsius. - -tempX_max Read/write the upper temperature limit - exceeding this - will cause an alarm. - -tempX_min Read/write the lower temperature limit - exceeding this - will cause an alarm. - -tempX_offset Read/write the temperature adjustment offset - -tempX_crit Read/write the THERM limit for remote1. - -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. - -tempX_auto_point1_temp Read/write the minimum temperature where the fans will - turn on in automatic mode. - -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. - -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 - -(There are two voltage settings, in1 and in2): - -inX_input Read the current voltage on VCC. Value is in - millivolts. - -inX_min read/write the minimum voltage limit. - Dropping below this causes an alarm. - -inX_max read/write the maximum voltage limit. - Exceeding this causes an alarm. - -inX_alarm Read a 1 if the max/min alarm is set. +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 + +Authors: + Jordan Crouse + Hans de Goede + Darrick J. Wong (documentation) + + +Description +----------- + +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. + +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. + +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. + +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. + +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. |