0001 Kernel driver g760a
0002 ===================
0003
0004 Supported chips:
0005
0006 * Global Mixed-mode Technology Inc. G760A
0007
0008 Prefix: 'g760a'
0009
0010 Datasheet: Publicly available at the GMT website
0011
0012 http://www.gmt.com.tw/product/datasheet/EDS-760A.pdf
0013
0014 Author: Herbert Valerio Riedel <hvr@gnu.org>
0015
0016 Description
0017 -----------
0018
0019 The GMT G760A Fan Speed PWM Controller is connected directly to a fan
0020 and performs closed-loop control of the fan speed.
0021
0022 The fan speed is programmed by setting the period via 'pwm1' of two
0023 consecutive speed pulses. The period is defined in terms of clock
0024 cycle counts of an assumed 32kHz clock source.
0025
0026 Setting a period of 0 stops the fan; setting the period to 255 sets
0027 fan to maximum speed.
0028
0029 The measured fan rotation speed returned via 'fan1_input' is derived
0030 from the measured speed pulse period by assuming again a 32kHz clock
0031 source and a 2 pulse-per-revolution fan.
0032
0033 The 'alarms' file provides access to the two alarm bits provided by
0034 the G760A chip's status register: Bit 0 is set when the actual fan
0035 speed differs more than 20% with respect to the programmed fan speed;
0036 bit 1 is set when fan speed is below 1920 RPM.
0037
0038 The g760a driver will not update its values more frequently than every
0039 other second; reading them more often will do no harm, but will return
0040 'old' values.
