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Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/devicetree/bindings/hwmon/g762.txt | 47 | ||||
| -rw-r--r-- | Documentation/hwmon/g762 | 65 |
2 files changed, 112 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/hwmon/g762.txt b/Documentation/devicetree/bindings/hwmon/g762.txt new file mode 100644 index 000000000000..25cc6d8ee575 --- /dev/null +++ b/Documentation/devicetree/bindings/hwmon/g762.txt @@ -0,0 +1,47 @@ +GMT G762/G763 PWM Fan controller + +Required node properties: + + - "compatible": must be either "gmt,g762" or "gmt,g763" + - "reg": I2C bus address of the device + - "clocks": a fixed clock providing input clock frequency + on CLK pin of the chip. + +Optional properties: + + - "fan_startv": fan startup voltage. Accepted values are 0, 1, 2 and 3. + The higher the more. + + - "pwm_polarity": pwm polarity. Accepted values are 0 (positive duty) + and 1 (negative duty). + + - "fan_gear_mode": fan gear mode. Supported values are 0, 1 and 2. + +If an optional property is not set in .dts file, then current value is kept +unmodified (e.g. u-boot installed value). + +Additional information on operational parameters for the device is available +in Documentation/hwmon/g762. A detailed datasheet for the device is available +at http://natisbad.org/NAS/refs/GMT_EDS-762_763-080710-0.2.pdf. + +Example g762 node: + + clocks { + #address-cells = <1>; + #size-cells = <0>; + + g762_clk: fixedclk { + compatible = "fixed-clock"; + #clock-cells = <0>; + clock-frequency = <8192>; + } + } + + g762: g762@3e { + compatible = "gmt,g762"; + reg = <0x3e>; + clocks = <&g762_clk> + fan_gear_mode = <0>; /* chip default */ + fan_startv = <1>; /* chip default */ + pwm_polarity = <0>; /* chip default */ + }; diff --git a/Documentation/hwmon/g762 b/Documentation/hwmon/g762 new file mode 100644 index 000000000000..923db9c5b5bc --- /dev/null +++ b/Documentation/hwmon/g762 @@ -0,0 +1,65 @@ +Kernel driver g762 +================== + +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 DC - are supported by the device. + +For additional information, a detailed datasheet is available at +http://natisbad.org/NAS/ref/GMT_EDS-762_763-080710-0.2.pdf. sysfs +bindings are described in Documentation/hwmon/sysfs-interface. + +The following entries are available to the user in a subdirectory of +/sys/bus/i2c/drivers/g762/ to control the operation of the device. +This can be done manually using the following entries but is usually +done via a userland daemon like fancontrol. + +Note that those entries do not provide ways to setup the specific +hardware characteristics of the system (reference clock, pulses per +fan revolution, ...); Those can be modified via devicetree bindings +documented in Documentation/devicetree/bindings/hwmon/g762.txt or +using a specific platform_data structure in board initialization +file (see include/linux/platform_data/g762.h). + + 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_div: fan clock divisor. Supported value are 1, 2, 4 and 8. + + fan1_pulses: number of pulses per fan revolution. Supported values + are 2 and 4. + + 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_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. + + pwm1_enable: set current fan speed control mode i.e. 1 for manual fan + speed control (open-loop) via pwm1 described below, 2 for + automatic fan speed control (closed-loop) via fan1_target + above. + + pwm1_mode: set or get fan driving mode: 1 for PWM mode, 0 for DC mode. + + pwm1: get or set PWM fan control value in open-loop mode. This is an + integer value between 0 and 255. 0 stops the fan, 255 makes + it run at full speed. + +Both in PWM mode ('pwm1_mode' set to 1) and DC mode ('pwm1_mode' set to 0), +when current fan speed control mode is open-loop ('pwm1_enable' set to 1), +the fan speed is programmed by setting a value between 0 and 255 via 'pwm1' +entry (0 stops the fan, 255 makes it run at full speed). In closed-loop mode +('pwm1_enable' set to 2), the expected rotation speed in RPM can be passed to +the chip via 'fan1_target'. In closed-loop mode, the target speed is compared +with current speed (available via 'fan1_input') by the device and a feedback +is performed to match that target value. The 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. |