Signed-off-by: Arnaud Ebalard <arno@xxxxxxxxxxxx> --- Documentation/hwmon/g762 | 89 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 89 insertions(+) create mode 100644 Documentation/hwmon/g762 diff --git a/Documentation/hwmon/g762 b/Documentation/hwmon/g762 new file mode 100644 index 0000000..f281b3d --- /dev/null +++ b/Documentation/hwmon/g762 @@ -0,0 +1,89 @@ +Kernel driver g762 +================== + +This documentation is based on G760a one, GMT G762 datasheet available +at http://natisbad.org/NAS/ref/GMT_EDS-762_763-080710-0.2.pdf (used +for the development of the driver) and sysfs bindings described in +Documentation/hwmon/sysfs-interface. + +The GMT G762 Fan Speed PWM Controller is connected directly to a fan +and performs closed-loop or open-loop control of the fan speed. Two +modes - PWM or linear - are supported by the device. + +The following entries are available to the user in a subdirectory of +/sys/bus/i2c/drivers/g762/ to control the operation of the device. +Some of those can be used to fit operations of the controller to the +characteristics of the system (reference clock value, fan gear mode, +number of pulses per fan revolution, ...). Other more common +parameters can be used to interact with the fan and control its speed +(set a rotation speed and get current speed for instance). This can be +done manually using the following entries but is usually done via a +userland daemon like fancontrol. + + + fan1_target: set desired fan speed. This only makes sense in closed-loop + fan speed control (i.e. when pwm1_enable is set to 2). + + fan1_input: provide current fan rotation value in RPM as reported by + the fan to the device. + + fan1_pulses: number of tachometer pulses per fan revolution. Supported + values are 2 and 4. Default value is 2. + + fan1_div: fan clock divisor. Supported value are 1, 2, 4 and 8. Default + value is 1. + + fan1_gear_mode: fan gear mode. Supported values are 0, 1 and 2. Default + value is 0. The value is a characteristic of the system + and a higher value can be set for more precisely control + fans with a high rotation speed. Note that this affects the + measurable speed range, not the read value. + + fan1_fault: reports fan failure, i.e. no transition on fan gear pin for + about 0.7s (if the fan is not voluntarily set off). + + fan1_fault_detection: enable fan failure detection and reporting as + described above. + + fan1_alarm: in closed-loop control mode, if fan RPM value is 25% out + of the programmed value for over 6 seconds 'fan1_alarm' is + set to 1. + + fan1_alarm_detection: enable fan out of control detection and reporting + as described above. + + fan1_startup_voltage: get or set fan startup voltage. Supported values + are 0, 1, 2, 3 (respectively for 1.0V, 1.5V, 2.0V and 2.5V). + + + + pwm1: get or set PWM fan control value. This is an integer value + between 0 and 255. 0 stops the fan, 255 makes it run at + full speed. + + pwm1_polarity: set or get the PWM polarity, 0 for positive duty, 1 for + negative duty + + pwm1_enable: set current fan speed control mode i.e. 1 for manual fan + speed control (open-loop), 2 for automatic fan speed control + (closed-loop). + + pwm1_mode: set or get fan driving mode: 1 for PWM mode, 0 for linear + mode. Default is linear mode. + + pwm1_freq: set or get value of PWM reference clock frequency. Default + value is 32768 (Hz). This parameter only makes sense when + the device is set to operate in PWM mode (i.e. pwm1_mode + is 1). + + +In PWM mode ('pwm1_mode' set to 1), the fan speed is programmed either by +setting a value between 0 and 255 via 'pwm1' entry (0 stops the fan, 255 +makes it run at full speed). This can also be done by passing the +expected RPM value via 'fan1_target'. Current fan speed value can be +retrieved via 'fan1_input'. This fan speed value is computed based on +the parameters associated with the physical characteristics of the +system: a reference clock source frequency, a number of pulses per fan +revolution, etc. + +Note that the driver will update its values at most once per second. -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
