| Kernel driver g760a |
| =================== |
| |
| Supported chips: |
| * Global Mixed-mode Technology Inc. G760A |
| Prefix: 'g760a' |
| Datasheet: Publicly available at the GMT website |
| http://www.gmt.com.tw/datasheet/g760a.pdf |
| |
| Author: Herbert Valerio Riedel <hvr@gnu.org> |
| |
| Description |
| ----------- |
| |
| The GMT G760A Fan Speed PWM Controller is connected directly to a fan |
| and performs closed-loop control of the fan speed. |
| |
| The fan speed is programmed by setting the period via 'pwm1' of two |
| consecutive speed pulses. The period is defined in terms of clock |
| cycle counts of an assumed 32kHz clock source. |
| |
| Setting a period of 0 stops the fan; setting the period to 255 sets |
| fan to maximum speed. |
| |
| The measured fan rotation speed returned via 'fan1_input' is derived |
| from the measured speed pulse period by assuming again a 32kHz clock |
| source and a 2 pulse-per-revolution fan. |
| |
| The 'alarms' file provides access to the two alarm bits provided by |
| the G760A chip's status register: Bit 0 is set when the actual fan |
| speed differs more than 20% with respect to the programmed fan speed; |
| bit 1 is set when fan speed is below 1920 RPM. |
| |
| The g760a driver will not update its values more frequently than every |
| other second; reading them more often will do no harm, but will return |
| 'old' values. |