1 Kernel driver g760a 2 =================== 3 4 Supported chips: 5 6 * Global Mixed-mode Technology Inc. G760A 7 8 Prefix: 'g760a' 9 10 Datasheet: Publicly available at the GMT website 11 12 http://www.gmt.com.tw/product/datasheet/EDS-760A.pdf 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.
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