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