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PWM

Introduction to PWM Configuration and Debugging

pinctrl​

You can refer to the configured pwm node settings in k1-x_pinctrl.dtsi located in the Linux repository under arch/riscv/boot/dts/spacemit/. The configuration is as follows:

   412     pinctrl_pwm0_1: pwm0_1_grp {
   413         pinctrl-single,pins =<
   414             K1X_PADCONF(GPIO_14, MUX_MODE3, (EDGE_NONE | PULL_UP | PAD_1V8_DS2))    /* pwm0 */
   415         >;
   416     };

dts configuration​

  • By default, all pwm nodes are configured, as shown in the following figure
1351         pwm0: pwm@d401a000 {
1352             compatible = "spacemit,k1x-pwm";
1353             reg = <0x0 0xd401a000 0x0 0x10>;
1354             #pwm-cells = <1>;
1355             clocks = <&ccu CLK_PWM0>;
1356             resets = <&reset RESET_PWM0>;
1357             k1x,pwm-disable-fd;
1358             status = "disabled";
1359         };
  • Enable the node in solution configuration, as follows: Enable the node and configure the pin node
807 &pwm0 {
808     pinctrl-names = "default";
809     pinctrl-0 = <&pinctrl_pwm0_1>;
810     status = "okay";
811 };

Debug​

The following verification is based on the bianbu linux system

# cd /sys/class/pwm/
# ls # Each node represents an led light
pwmchip0  pwmchip1  pwmchip2  pwmchip3  pwmchip4  pwmchip5  pwmchip6

# echo 0 > pwmchip0/export
# ls pwmchip0/pwm0/
capture     enable      polarity    uevent
duty_cycle  period      power

# The unit is ns, that is, a period is 1KHZ
# echo 1000000 > pwmchip0/pwm0/period 

# Set PWM duty cycle
# echo 500000 > pwmchip0/pwm0/duty_cycle 

# enable PWM
# echo 1 > pwmchip0/pwm0/enable 

# Adjust duty cycle, this time the brightness decreases
# echo 50000 > pwmchip0/pwm0/duty_cycle 

# disable PWM
# echo 0 > pwmchip0/pwm0/enable