overlays: Add overlay pwm1

pwm1 enables the second PWM interface found on BCM2711. It can only
be mapped to GPIOs 40 & 41.

See: https://forums.raspberrypi.com/viewtopic.php?t=342458

Signed-off-by: Phil Elwell <phil@raspberrypi.com>

arch/arm/boot/dts/overlays/Makefile

@@ -183,6 +183,7 @@ dtbo-$(CONFIG_ARCH_BCM2835) += \
 	pwm.dtbo \
 	pwm-2chan.dtbo \
 	pwm-ir-tx.dtbo \
+	pwm1.dtbo \
 	qca7000.dtbo \
 	qca7000-uart0.dtbo \
 	ramoops.dtbo \

arch/arm/boot/dts/overlays/README

@@ -3216,6 +3216,24 @@ Params: gpio_pin                Output GPIO (default 18)
         func                    Pin function (default 2 = Alt5)
 
 
+Name:   pwm1
+Info:   Configures one or two PWM channel on PWM1 (BCM2711 only)
+        N.B.:
+          1) The onboard analogue audio output uses both PWM channels.
+          2) So be careful mixing audio and PWM.
+        Note that even when only one pin is enabled, both channels are available
+        from the PWM driver, so be careful to use the correct one.
+Load:   dtoverlay=pwm1,<param>=<val>
+Params: clock                   PWM clock frequency (informational)
+        pins_40                 Enable channel 0 (PWM1_0) on GPIO 40
+        pins_41                 Enable channel 1 (PWM1_1) on GPIO 41
+        pins_40_41              Enable channels 0 (PWM1_0) and 1 (PW1_1) on
+                                GPIOs 40 and 41 (default)
+        pull_up                 Enable pull-ups on the PWM pins (default)
+        pull_down               Enable pull-downs on the PWM pins
+        pull_off                Disable pulls on the PWM pins
+
+
 Name:   qca7000
 Info:   in-tech's Evaluation Board for PLC Stamp micro
         This uses spi0 and a separate GPIO interrupt to connect the QCA7000.

arch/arm/boot/dts/overlays/overlay_map.dts

@@ -77,6 +77,10 @@
 		renamed = "miniuart-bt";
 	};
 
+	pwm1 {
+		bcm2711;
+	};
+
 	ramoops {
 		bcm2835;
 		bcm2711 = "ramoops-pi4";

arch/arm/boot/dts/overlays/pwm1-overlay.dts

@@ -0,0 +1,60 @@
+/dts-v1/;
+/plugin/;
+
+#include <dt-bindings/pinctrl/bcm2835.h>
+
+/ {
+	compatible = "brcm,bcm2711";
+
+	fragment@0 {
+		target = <&pins>;
+		__overlay__ {
+			brcm,pins = <40 41>;
+		};
+	};
+
+	fragment@1 {
+		target = <&pins>;
+		__dormant__ {
+			brcm,pins = <40>;
+		};
+	};
+
+	fragment@2 {
+		target = <&pins>;
+		__dormant__ {
+			brcm,pins = <41>;
+		};
+	};
+
+	fragment@3 {
+		target = <&gpio>;
+		__overlay__ {
+			pins: pwm1_overlay_pins {
+				brcm,pins = <40 41>;
+				brcm,function = <BCM2835_FSEL_ALT0>;
+				brcm,pull = <BCM2835_PUD_UP>;
+			};
+		};
+	};
+
+	fragment@4 {
+		target = <&pwm1>;
+		pwm: __overlay__ {
+			status = "okay";
+			assigned-clock-rates = <100000000>;
+			pinctrl-names = "default";
+			pinctrl-0 = <&pins>;
+		};
+	};
+
+	__overrides__ {
+		clock = <&pwm>, "assigned-clock-rates:0";
+		pins_40_41 = <0>,"+0-1-2";
+		pins_40 = <0>,"-0+1-2";
+		pins_41 = <0>,"-0-1+2";
+		pull_up = <&pins>, "brcm,pull:0=", <BCM2835_PUD_UP>;
+		pull_down = <&pins>, "brcm,pull:0=", <BCM2835_PUD_DOWN>;
+		pull_off = <&pins>, "brcm,pull:0=", <BCM2835_PUD_OFF>;
+	};
+};