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Based on kernel version 3.13. Page generated on 2014-01-20 22:03 EST.

1	Kernel driver g762
2	==================
4	The GMT G762 Fan Speed PWM Controller is connected directly to a fan
5	and performs closed-loop or open-loop control of the fan speed. Two
6	modes - PWM or DC - are supported by the device.
8	For additional information, a detailed datasheet is available at
9	http://natisbad.org/NAS/ref/GMT_EDS-762_763-080710-0.2.pdf. sysfs
10	bindings are described in Documentation/hwmon/sysfs-interface.
12	The following entries are available to the user in a subdirectory of
13	/sys/bus/i2c/drivers/g762/ to control the operation of the device.
14	This can be done manually using the following entries but is usually
15	done via a userland daemon like fancontrol.
17	Note that those entries do not provide ways to setup the specific
18	hardware characteristics of the system (reference clock, pulses per
19	fan revolution, ...); Those can be modified via devicetree bindings
20	documented in Documentation/devicetree/bindings/hwmon/g762.txt or
21	using a specific platform_data structure in board initialization
22	file (see include/linux/platform_data/g762.h).
24	  fan1_target: set desired fan speed. This only makes sense in closed-loop
25	            fan speed control (i.e. when pwm1_enable is set to 2).
27	  fan1_input: provide current fan rotation value in RPM as reported by
28	            the fan to the device.
30	  fan1_div: fan clock divisor. Supported value are 1, 2, 4 and 8.
32	  fan1_pulses: number of pulses per fan revolution. Supported values
33	            are 2 and 4.
35	  fan1_fault: reports fan failure, i.e. no transition on fan gear pin for
36	            about 0.7s (if the fan is not voluntarily set off).
38	  fan1_alarm: in closed-loop control mode, if fan RPM value is 25% out
39	            of the programmed value for over 6 seconds 'fan1_alarm' is
40	            set to 1.
42	  pwm1_enable: set current fan speed control mode i.e. 1 for manual fan
43	            speed control (open-loop) via pwm1 described below, 2 for
44	            automatic fan speed control (closed-loop) via fan1_target
45	            above.
47	  pwm1_mode: set or get fan driving mode: 1 for PWM mode, 0 for DC mode.
49	  pwm1: get or set PWM fan control value in open-loop mode. This is an
50	            integer value between 0 and 255. 0 stops the fan, 255 makes
51	            it run at full speed.
53	Both in PWM mode ('pwm1_mode' set to 1) and DC mode ('pwm1_mode' set to 0),
54	when current fan speed control mode is open-loop ('pwm1_enable' set to 1),
55	the fan speed is programmed by setting a value between 0 and 255 via 'pwm1'
56	entry (0 stops the fan, 255 makes it run at full speed). In closed-loop mode
57	('pwm1_enable' set to 2), the expected rotation speed in RPM can be passed to
58	the chip via 'fan1_target'. In closed-loop mode, the target speed is compared
59	with current speed (available via 'fan1_input') by the device and a feedback
60	is performed to match that target value. The fan speed value is computed
61	based on the parameters associated with the physical characteristics of the
62	system: a reference clock source frequency, a number of pulses per fan
63	revolution, etc.
65	Note that the driver will update its values at most once per second.
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