I have used GPIO8 for SD Detect,and assigned FAN_TACH to PIN228, I have changed the device tree and enabled the SDMMC3,when i set the pwm PWM_duty_cycle and the fan worked well,but can not get the fan speed
cat /sys/devices/generic_pwm_tachometer/hwmon/hwmon1/rpm
it alwys get 0.
i can not find any info about gpio_tachometer:
Device tree bindings for fan tach output connected to IRQ capable GPIO.
Required properties:
- compatible : "nvidia,gpio-tachometer"
- win-len : Duration in multiples of 100ms, for which the IRQ will be enabled
while measuring speed. Maximum allowed value is 5 seconds to avoid
possible IRQ overload at high speed.
- pulse-per-rev : Number of signals generated on the tach output pin by the motor
for one full rotation.
- gpio : GPIO pin on which tach output of the motor is connected.
Optional properties:
- schedule-delay: Time in milliseconds for the background thread to monitor the speed.
If the measured speed is 0, system shutdown will be initiated.
Time duration should be higher than win-len time.
Example:
gpio_tachometer {
compatible = "nvidia,gpio-tachometer";
win-len = <2>; /*For every measurement, take samples for 200ms*/
pulse-per-rev = <2>; /*Motor generates 2 pulses for every full rotation*/
schedule-delay = <10000>; /*Check motor speed every 10seconds and shutdown if motor is stopped*/
gpio = <&tegra_main_gpio TEGRA_MAIN_GPIO(Y, 1) 0>;
status = "okay";
};