[PATCH] arm64: dts: rockchip: Enable audio on DFRobot UNIHIKER M10 V1.2

[Miotsuki Mizuno <founder@crepuse.com>]

Enable the internal RK3308 codec and its I2S2 interface, and add a
simple-audio-card. Route the onboard microphone to MIC1 and supply it
from MICBIAS1, with the bias set to 85 percent of AVDD as used during
board bring-up.

The board does not expose a speaker interface, so no speaker routing
is added.

The board uses codec revision B. Support has been accepted in the ASoC
for-7.4 branch as commit 157f7cba77a9 ("ASoC: codecs: rk3308: add support
for codec revision B"). This is a runtime dependency; the DTS uses the
existing codec compatible and bindings.

Signed-off-by: Mizuno Miotsuki <founder@crepuse.com>
---
Based on Heiko's v7.4-armsoc/dts64 branch. The codec revision-B driver
support is in Mark Brown's ASoC for-7.4 branch (157f7cba77a9); there is
no build-time or binding dependency on that change.

The same microphone route and 85-percent bias setting were used during
V1.2 bring-up. Codec registration and onboard microphone capture were
verified then, with the recording confirmed by listening. PCM/DAPM
checks were also performed with the preceding codec candidate; physical
LINEOUT and HPOUT audio were not tested. The final accepted codec
shared-output implementation was compile-tested only.

Validation of this patch:
- Target DTB build: PASS (arm64 defconfig, aarch64-linux-gnu-gcc).
- Target dtbs_check against all bindings: PASS, no diagnostics
  (dtschema 2026.9, CHECK_DTBS=y).
- Strict checkpatch: PASS, 0 errors, 0 warnings, 0 checks.

 .../dts/rockchip/rk3308-unihiker-m10-v1.2.dts | 30 +++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/arch/arm64/boot/dts/rockchip/rk3308-unihiker-m10-v1.2.dts b/arch/arm64/boot/dts/rockchip/rk3308-unihiker-m10-v1.2.dts
index 270ea970c95a..7adef454ea89 100644
--- a/arch/arm64/boot/dts/rockchip/rk3308-unihiker-m10-v1.2.dts
+++ b/arch/arm64/boot/dts/rockchip/rk3308-unihiker-m10-v1.2.dts
@@ -54,6 +54,26 @@ sdio_pwrseq: sdio-pwrseq {
 		reset-gpios = <&gpio0 RK_PA2 GPIO_ACTIVE_LOW>;
 	};
 
+	sound {
+		compatible = "simple-audio-card";
+		simple-audio-card,name = "UNIHIKER M10 RK3308 codec";
+		simple-audio-card,format = "i2s";
+		simple-audio-card,mclk-fs = <256>;
+		simple-audio-card,widgets =
+			"Microphone", "Internal Microphone";
+		simple-audio-card,routing =
+			"Internal Microphone", "MICBIAS1",
+			"MIC1", "Internal Microphone";
+
+		simple-audio-card,cpu {
+			sound-dai = <&i2s_8ch_2>;
+		};
+
+		simple-audio-card,codec {
+			sound-dai = <&codec>;
+		};
+	};
+
 	vcc_1v8: regulator-vcc-1v8 {
 		compatible = "regulator-fixed";
 		regulator-name = "vcc_1v8";
@@ -117,6 +137,11 @@ vdd_core: regulator-vdd-core {
 	};
 };
 
+&codec {
+	rockchip,micbias-avdd-percent = <85>;
+	status = "okay";
+};
+
 &cpu0 {
 	cpu-supply = <&vdd_core>;
 };
@@ -131,6 +156,11 @@ &emmc {
 	status = "okay";
 };
 
+&i2s_8ch_2 {
+	#sound-dai-cells = <0>;
+	status = "okay";
+};
+
 &io_domains {
 	vccio0-supply = <&vcc_io>;
 	vccio1-supply = <&vcc_io>;

base-commit: f204f28bd1fa9b4cf3e47488ba3ba25251aba18a
-- 
2.56.0