projects / linux-block.git / blame
| Commit | Line | Data |
|---|---|---|
| 3bcfa9e4 HVR |
1 | Kernel driver g760a |
| 2 | =================== | |
| 3 | ||
| 4 | Supported chips: | |
| b04f2f7d | 5 | |
| 3bcfa9e4 | 6 | * Global Mixed-mode Technology Inc. G760A |
| b04f2f7d | 7 | |
| 3bcfa9e4 | 8 | Prefix: 'g760a' |
| b04f2f7d | 9 | |
| 3bcfa9e4 | 10 | Datasheet: Publicly available at the GMT website |
| b04f2f7d | 11 | |
| 0ea6e611 | 12 | http://www.gmt.com.tw/product/datasheet/EDS-760A.pdf |
| 3bcfa9e4 HVR |
13 | |
| 14 | Author: Herbert Valerio Riedel <hvr@gnu.org> | |
| 15 | ||
| 16 | Description | |
| 17 | ----------- | |
| 18 | ||
| 19 | The GMT G760A Fan Speed PWM Controller is connected directly to a fan | |
| 20 | and performs closed-loop control of the fan speed. | |
| 21 | ||
| 22 | The fan speed is programmed by setting the period via 'pwm1' of two | |
| 23 | consecutive speed pulses. The period is defined in terms of clock | |
| 24 | cycle counts of an assumed 32kHz clock source. | |
| 25 | ||
| 26 | Setting a period of 0 stops the fan; setting the period to 255 sets | |
| 27 | fan to maximum speed. | |
| 28 | ||
| 29 | The measured fan rotation speed returned via 'fan1_input' is derived | |
| 30 | from the measured speed pulse period by assuming again a 32kHz clock | |
| 31 | source and a 2 pulse-per-revolution fan. | |
| 32 | ||
| 33 | The 'alarms' file provides access to the two alarm bits provided by | |
| 34 | the G760A chip's status register: Bit 0 is set when the actual fan | |
| 35 | speed differs more than 20% with respect to the programmed fan speed; | |
| 36 | bit 1 is set when fan speed is below 1920 RPM. | |
| 37 | ||
| 38 | The g760a driver will not update its values more frequently than every | |
| 39 | other second; reading them more often will do no harm, but will return | |
| 40 | 'old' values. |