Based on kernel version 3.12. Page generated on 2013-11-13 21:58 EST.
1 Kernel driver g762 2 ================== 3 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. 7 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. 11 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. 16 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). 23 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). 26 27 fan1_input: provide current fan rotation value in RPM as reported by 28 the fan to the device. 29 30 fan1_div: fan clock divisor. Supported value are 1, 2, 4 and 8. 31 32 fan1_pulses: number of pulses per fan revolution. Supported values 33 are 2 and 4. 34 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). 37 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. 41 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. 46 47 pwm1_mode: set or get fan driving mode: 1 for PWM mode, 0 for DC mode. 48 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. 52 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. 64 65 Note that the driver will update its values at most once per second.