boards: arm: rpi_pico: add pwm bindings to devictree

Add bindings for pwm-leds to the rpi pico board. The default
pwm binding is connected to the onboard LED (P25).

Signed-off-by: Joep Buruma <burumaj50@gmail.com>

boards/arm/rpi_pico/doc/index.rst

@@ -70,6 +70,9 @@ hardware features:
    * - Watchdog Timer (WDT)
      - :kconfig:option:`CONFIG_WATCHDOG`
      - :dtcompatible:`raspberrypi,pico-watchdog`
+   * - PWM
+     - :kconfig: `CONFIG_PWM`
+     - :dtcompatible: `raspberrypi,pico-pwm`
 
 Programming and Debugging
 *************************

boards/arm/rpi_pico/rpi_pico-pinctrl.dtsi

@@ -31,4 +31,10 @@
 			input-schmitt-enable;
 		};
 	};
+
+	pwm_ch4b_default: pwm_ch4b_default {
+		group1 {
+			pinmux = <PWM_4B_P25>;
+		};
+	};
 };

boards/arm/rpi_pico/rpi_pico.dts

@@ -8,6 +8,7 @@
 
 #include <rpi_pico/rp2040.dtsi>
 #include "rpi_pico-pinctrl.dtsi"
+#include <dt-bindings/pwm/pwm.h>
 
 #include <zephyr/dt-bindings/i2c/i2c.h>
 
@@ -34,9 +35,19 @@
 		#clock-cells = <0>;
 	};
 
+	pwm_leds {
+		compatible = "pwm-leds";
+		pwm_led0: pwm_led_0 {
+			status = "disabled";
+			pwms = <&pwm 9 PWM_MSEC(20) PWM_POLARITY_NORMAL>;
+			label = "PWM_LED";
+		};
+	};
+
 	aliases {
 		led0 = &led0;
 		watchdog0 = &wdt0;
+		pwm-led0 = &pwm_led0;
 	};
 };
 
@@ -99,3 +110,9 @@
 zephyr_udc0: &usbd {
 	status = "okay";
 };
+
+&pwm {
+	pinctrl-0 = <&pwm_ch4b_default>;
+	pinctrl-names = "default";
+	divider-int-0 = <255>;
+};

boards/arm/rpi_pico/rpi_pico.yaml

@@ -14,3 +14,4 @@ supported:
   - i2c
   - hwinfo
   - watchdog
+  - pwm