| Darrick J. Wong | c0b4e3a | 2008-11-12 13:27:03 -0800 | [diff] [blame] | 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 | |