projects / deliverable / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| c0b4e3ab DW |
1 | Kernel driver adt7462 |
| 2 | ====================== | |
| 3 | ||
| 4 | Supported chips: | |
| 5 | * Analog Devices ADT7462 | |
| 6 | Prefix: 'adt7462' | |
| 7 | Addresses scanned: I2C 0x58, 0x5C | |
| 8 | Datasheet: Publicly available at the Analog Devices website | |
| 9 | ||
| 10 | Author: Darrick J. Wong | |
| 11 | ||
| 12 | Description | |
| 13 | ----------- | |
| 14 | ||
| 15 | This driver implements support for the Analog Devices ADT7462 chip family. | |
| 16 | ||
| 17 | This chip is a bit of a beast. It has 8 counters for measuring fan speed. It | |
| 18 | can also measure 13 voltages or 4 temperatures, or various combinations of the | |
| 19 | two. See the chip documentation for more details about the exact set of | |
| 20 | configurations. This driver does not allow one to configure the chip; that is | |
| 21 | left to the system designer. | |
| 22 | ||
| 23 | A sophisticated control system for the PWM outputs is designed into the ADT7462 | |
| 24 | that allows fan speed to be adjusted automatically based on any of the three | |
| 25 | temperature sensors. Each PWM output is individually adjustable and | |
| 26 | programmable. Once configured, the ADT7462 will adjust the PWM outputs in | |
| 27 | response to the measured temperatures without further host intervention. This | |
| 28 | feature can also be disabled for manual control of the PWM's. | |
| 29 | ||
| 30 | Each of the measured inputs (voltage, temperature, fan speed) has | |
| 31 | corresponding high/low limit values. The ADT7462 will signal an ALARM if | |
| 32 | any measured value exceeds either limit. | |
| 33 | ||
| 34 | The ADT7462 samples all inputs continuously. The driver will not read | |
| 35 | the registers more often than once every other second. Further, | |
| 36 | configuration data is only read once per minute. | |
| 37 | ||
| 38 | Special Features | |
| 39 | ---------------- | |
| 40 | ||
| 41 | The ADT7462 have a 10-bit ADC and can therefore measure temperatures | |
| 42 | with 0.25 degC resolution. | |
| 43 | ||
| 44 | The Analog Devices datasheet is very detailed and describes a procedure for | |
| 45 | determining an optimal configuration for the automatic PWM control. | |
| 46 | ||
| 47 | The driver will report sensor labels when it is able to determine that | |
| 48 | information from the configuration registers. | |
| 49 | ||
| 50 | Configuration Notes | |
| 51 | ------------------- | |
| 52 | ||
| 53 | Besides standard interfaces driver adds the following: | |
| 54 | ||
| 55 | * PWM Control | |
| 56 | ||
| 57 | * pwm#_auto_point1_pwm and temp#_auto_point1_temp and | |
| 58 | * pwm#_auto_point2_pwm and temp#_auto_point2_temp - | |
| 59 | ||
| 60 | point1: Set the pwm speed at a lower temperature bound. | |
| 61 | point2: Set the pwm speed at a higher temperature bound. | |
| 62 | ||
| 63 | The ADT7462 will scale the pwm between the lower and higher pwm speed when | |
| 64 | the temperature is between the two temperature boundaries. PWM values range | |
| 65 | from 0 (off) to 255 (full speed). Fan speed will be set to maximum when the | |
| 66 | temperature sensor associated with the PWM control exceeds temp#_max. | |
| 67 |