dts: overlays: Enable RP1 Audio Out using audremap-pi5-overlay

Since RP1 Audio Out can only work on GPIOs 12, 13 which would
previously have needed dtoverlay=audremap, overload it both to
enable and pin-map the block (do not enable for other pinouts).

At the same time, generate a default "codec" and "sound card".

Signed-off-by: Nick Hollinghurst <nick.hollinghurst@raspberrypi.com>

Author: njhollinghurst

arch/arm/boot/dts/overlays/Makefile

@@ -33,6 +33,7 @@ dtbo-$(CONFIG_ARCH_BCM2835) += \
 	audioinjector-wm8731-audio.dtbo \
 	audiosense-pi.dtbo \
 	audremap.dtbo \
+	audremap-pi5.dtbo \
 	balena-fin.dtbo \
 	bcm2712d0.dtbo \
 	camera-mux-2port.dtbo \

arch/arm/boot/dts/overlays/README

@@ -871,6 +871,17 @@ Params: swap_lr                 Reverse the channel allocation, which will also
                                 pins are on different controllers)
 
 
+Name:   audremap-pi5
+Info:   On Raspberry Pi 5 / 500 /CM5, enable digital audio output
+        and route it to GPIOs 12 & 13 on the 40-pin header
+Load:   dtoverlay=audremap-pi5,<param>=<val>
+Params: swap_lr                 Reverse the channel allocation (default off)
+        pins_12_13              Select GPIOs 12 & 13 (default)
+        pins_18_19              Not available; this will not enable audio out
+        pins_40_41              Not available; this will not enable audio out
+        pins_40_45              Not available; this will not enable audio out
+
+
 Name:   balena-fin
 Info:   Overlay that enables WLAN, Bluetooth and the GPIO expander on the
         balenaFin carrier board for the Raspberry Pi Compute Module 3/3+ Lite.

arch/arm/boot/dts/overlays/audremap-pi5-overlay.dts

@@ -0,0 +1,65 @@
+/dts-v1/;
+/plugin/;
+
+/*
+ * Raspberry Pi 5 has a different Audio Out hardware from earlier Raspberry Pis.
+ * It can output only to GPIOs 12 and 13. We therefore enable it *only* when
+ * that particular GPIO mapping is requested here. To make it work with ASOC
+ * we must also define a "dummy" codec and a generic audio card.
+ */
+
+/ {
+	compatible = "brcm,bcm2712";
+
+	fragment@0 {
+		target = <&rp1_audio_out>;
+		frag0: __overlay__ {
+			pinctrl-0 = <&rp1_audio_out_12_13>;
+			pinctrl-names = "default";
+			status = "ok";
+		};
+	};
+
+	fragment@1 {
+		 target-path = "/";
+		 __overlay__ {
+
+			 rp1_audio_out_codec: rp1_audio_out_codec@0 {
+			     compatible = "linux,spdif-dit";
+			     #sound-dai-cells = <0>;
+			     status = "ok";
+			 };
+
+			 rp1_audio_out_simple_card@0 {
+			     compatible = "simple-audio-card";
+			     simple-audio-card,name = "RP1-Audio-Out";
+			     #address-cells = <1>;
+			     #size-cells = <0>;
+			     status = "ok";
+
+			     simple-audio-card,dai-link@0 {
+				 reg = <0>;
+				 format = "left_j";
+				 bitclock-master = <&sndcpu0>;
+				 frame-master = <&sndcpu0>;
+
+				sndcpu0: cpu {
+					sound-dai = <&rp1_audio_out>;
+				};
+
+				codec {
+				    sound-dai = <&rp1_audio_out_codec>;
+				};
+			    };
+			};
+		};
+	};
+
+	__overrides__ {
+		swap_lr = <&frag0>, "swap_lr?";
+		pins_12_13 = <0>, "+0+1"; /* this is the default */
+		pins_18_19 = <0>, "-0-1"; /* sorry not supported */
+		pins_40_41 = <0>, "-0-1"; /* sorry not supported */
+		pins_40_45 = <0>, "-0-1"; /* sorry not supported */
+	};
+};

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

@@ -4,6 +4,11 @@
 	audremap {
 		bcm2835;
 		bcm2711;
+		bcm2712 = "audremap-pi5";
+	};
+
+	audremap-pi5 {
+		bcm2712;
 	};
 
 	balena-fin {