overlays: Add support for pps-rp1 dtoverlay

Add support for pps-rp1 dtoverlay. Enables advanced pinctrl features
found on RP1 based RPis and echo out functionality in the pps-gpio
kernel module.

Signed-off-by: Josh Blake <mail@josh.to>

Author: josh-blake

arch/arm/boot/dts/overlays/Makefile

@@ -227,6 +227,7 @@ dtbo-$(CONFIG_ARCH_BCM2835) += \
 	pitft35-resistive.dtbo \
 	pivision.dtbo \
 	pps-gpio.dtbo \
+	pps-rp1.dtbo \
 	proto-codec.dtbo \
 	pwm.dtbo \
 	pwm-2chan.dtbo \

arch/arm/boot/dts/overlays/README

@@ -4152,6 +4152,52 @@ Params: gpiopin                 Input GPIO (default "18")
                                 Default is "off".
 
 
+Name:   pps-rp1
+
+Info:   Configures the pps-gpio kernel module for use with the RP1 found on the
+        RPi 5 (pulse-per-second time signal via GPIO).
+
+Load:   dtoverlay=pps-rp1,<param>=<val>
+
+Params: pin                     (integer) Specifies the PPS input pin.
+                                Takes the pin number correlating to the RPi
+                                40-pin GPIO header.
+                                Defaults to GPIO 18.
+
+        pull-none               (boolean) Disable pull-up/down resistors on the
+                                PPS input pin.
+
+        pull-up                 (boolean) Enable pull-up resistor on the PPS
+                                input pin.
+
+        pull-down               (boolean) Enable pull-down resistor on the PPS
+                                input pin.
+
+        schmitt-trigger         (boolean) Enable the Schmitt-trigger on the PPS
+                                input pin.
+                                Defaults to off.
+
+        echo-pin                (integer) Specifies the PPS echo output pin.
+                                Takes the pin number correlating to the RPi
+                                40-pin GPIO header.
+                                Defaults to GPIO 17.
+
+        echo-ms                 (integer) Specifies the pulse-width in ms of the
+                                echo signal on the PPS echo output pin.
+                                Must be less than 999.
+                                Defaults to 10ms.
+
+        echo                    (boolean) Enables the PPS echo output signal.
+                                Defaults to off.
+
+        capture-clear           (boolean) Captures the clear event time.
+                                Defaults to off.
+
+        assert-falling-edge     (boolean) Trigger on the falling signal edge
+                                instead of the rising signal edge.
+                                Defaults to off.
+
+
 Name:   proto-codec
 Info:   Configures the PROTO Audio Codec card
 Load:   dtoverlay=proto-codec

arch/arm/boot/dts/overlays/pps-rp1-overlay.dts

@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// This file is released under the GPL v2.0 License, and comes without warranty, express or implied.
+// (C) Josh Blake, 2026
+
+/*
+ *	dtparams:
+ *	pin: (integer) Specifies the PPS Input pin.
+ *		Takes the pin number correlating to the RPi 40-pin GPIO.
+ *		Defaults to GPIO 18.
+ *	pull-none: (boolean) Disable pull-up/down resistors on the PPS Input pin.
+ *	pull-up: (boolean) Enable pull-up resistor on the PPS Input pin.
+ *	pull-down: (boolean) Enable pull-down resistor on the PPS Input pin.
+ *	schmitt-trigger: (boolean) Enable the Schmitt-trigger on the PPS Input pin.
+ *		Defaults to off.
+ *	echo-pin: (integer) Specifies the PPS Echo Output pin.
+ *		Takes the pin number correlating to the RPi 40-pin GPIO.
+ *		Defaults to GPIO 17.
+ *	echo-ms: (integer) Specifies the pulse-width in ms that the echo signal outputs
+ *		on the PPS Echo Output pin.
+ *		Must be less than 999.
+ *		Defaults to 10ms.
+ *	echo: (boolean) Enables the PPS Echo Output signal.
+ *		Defaults to off.
+ *	capture-clear: (boolean) Captures the clear event time.
+ *		Defaults to off.
+ *	assert-falling-edge: (boolean) Uses the falling signal edge instead of the
+ *		rising signal edge.
+ *		Defaults to off.
+ */
+
+/dts-v1/;
+/plugin/;
+
+/ {
+	compatible = "brcm,bcm2712";
+
+	fragment@0 {
+		target-path = "/";
+		__overlay__ {
+			pps: pps@ {
+				compatible = "pps-gpio";
+				pinctrl-names = "default";
+				pinctrl-0 = <&pps_gpios>;
+				gpios = <&gpio 18 0>;
+				status = "okay";
+			};
+		};
+	};
+
+	fragment@1 {
+		target = <&gpio>;
+		__overlay__ {
+			pps_gpios: pps_gpios@ {
+				pps_in: pps_in@ {
+					function = "gpio";
+					input-enable;
+				};
+			};
+		};
+	};
+
+	fragment@2 {
+		target = <&pps_gpios>;
+		__dormant__ {
+			pps_out: pps_out@ {
+				function = "gpio";
+				output-enable;
+				drive-push-pull;
+				bias-disable;
+			};
+		};
+	};
+
+	fragment@3 {
+		target = <&pps>;
+		pps_echo: __dormant__ {
+			echo-gpios = <&gpio 17 0>;
+			echo-active-ms = <10>;
+		};
+	};
+
+	__overrides__ {
+	// A very annoying and inelegant pinctrl to pin number LUT
+		pin =
+			<&pps>,"reg:0{,=18}",
+			<&pps>,"gpios:4{,=18}",
+			<&pps_gpios>,"reg:0{,=18}",
+			<&pps_in>,"reg:0{,=18}",
+			<&pps_in>,"pins{2=gpio2,3=gpio3,4=gpio4,17=gpio17,27=gpio27,22=gpio22,10=gpio10,9=gpio9,11=gpio11,0=gpio0,5=gpio5,6=gpio6,13=gpio13,19=gpio19,26=gpio26,14=gpio14,15=gpio15,18=gpio18,23=gpio23,24=gpio24,25=gpio25,8=gpio8,7=gpio7,1=gpio1,12=gpio12,16=gpio16,20=gpio20,21=gpio21,=gpio18}";
+		pull-none = <&pps_in>,"bias-disable?";
+		pull-up = <&pps_in>,"bias-pull-up?";
+		pull-down = <&pps_in>,"bias-pull-down?";
+		schmitt-trigger = <&pps_in>,"input-enable!",<&pps_in>,"input-schmitt-enable?";
+		assert-falling-edge = <&pps>,"assert-falling-edge?";
+		capture-clear = <&pps>,"capture-clear?";
+		echo-pin =
+			<&pps_out>,"reg:0{,=17}",
+			<&pps_out>,"pins{2=gpio2,3=gpio3,4=gpio4,17=gpio17,27=gpio27,22=gpio22,10=gpio10,9=gpio9,11=gpio11,0=gpio0,5=gpio5,6=gpio6,13=gpio13,19=gpio19,26=gpio26,14=gpio14,15=gpio15,18=gpio18,23=gpio23,24=gpio24,25=gpio25,8=gpio8,7=gpio7,1=gpio1,12=gpio12,16=gpio16,20=gpio20,21=gpio21,=gpio17}",
+			<&pps_echo>,"echo-gpios:4{,=17}";
+		echo-ms = <&pps_echo>,"echo-active-ms:0";
+		echo = <0>,"+2+3";
+	};
+};