[PATCH v3] arm64: dts: renesas: r8a779g3: Add Argon40 fan HAT DTO to Retronix R-Car V4H Sparrow Hawk

[Marek Vasut]

Add DT overlay to bind Argon40 fan HAT, on Retronix R-Car V4H
Sparrow Hawk board. Fan RPM control and full RPM on reboot has
been tested.

Tested-by: Wolfram Sang <wsa+renesas at sang-engineering.com>
Signed-off-by: Marek Vasut <marek.vasut+renesas at mailbox.org>
---
Cc: Conor Dooley <conor+dt at kernel.org>
Cc: Geert Uytterhoeven <geert+renesas at glider.be>
Cc: Krzysztof Kozlowski <krzk+dt at kernel.org>
Cc: Magnus Damm <magnus.damm at gmail.com>
Cc: Rob Herring <robh at kernel.org>
Cc: devicetree at vger.kernel.org
Cc: linux-renesas-soc at vger.kernel.org
---
NOTE: Depends on series:
      https://lore.kernel.org/linux-hwmon/20250904202157.170600-1-marek.vasut+renesas@mailbox.org/
---
V2: - Rename the pwm-fan node to pwm-fan-ext to avoid colission
      with existing pwm-fan node in r8a779g3-sparrow-hawk.dts .
      There can be two independent blower fans.
V3: - Add TB from Wolfram
    - Rework the list of hwmon devices in example
---
 arch/arm64/boot/dts/renesas/Makefile          |  3 ++
 .../r8a779g3-sparrow-hawk-fan-argon40.dtso    | 51 +++++++++++++++++++
 2 files changed, 54 insertions(+)
 create mode 100644 arch/arm64/boot/dts/renesas/r8a779g3-sparrow-hawk-fan-argon40.dtso

diff --git a/arch/arm64/boot/dts/renesas/Makefile b/arch/arm64/boot/dts/renesas/Makefile
index bef624636d58b..b2325d1ddf9d3 100644
--- a/arch/arm64/boot/dts/renesas/Makefile
+++ b/arch/arm64/boot/dts/renesas/Makefile
@@ -96,6 +96,9 @@ dtb-$(CONFIG_ARCH_R8A779G0) += r8a779g2-white-hawk-single-ard-audio-da7212.dtb
 
 DTC_FLAGS_r8a779g3-sparrow-hawk += -Wno-spi_bus_bridge
 dtb-$(CONFIG_ARCH_R8A779G0) += r8a779g3-sparrow-hawk.dtb
+dtb-$(CONFIG_ARCH_R8A779G0) += r8a779g3-sparrow-hawk-fan-argon40.dtbo
+r8a779g3-sparrow-hawk-fan-argon40-dtbs := r8a779g3-sparrow-hawk.dtb r8a779g3-sparrow-hawk-fan-argon40.dtbo
+dtb-$(CONFIG_ARCH_R8A779G0) += r8a779g3-sparrow-hawk-fan-argon40.dtb
 dtb-$(CONFIG_ARCH_R8A779G0) += r8a779g3-sparrow-hawk-fan-pwm.dtbo
 r8a779g3-sparrow-hawk-fan-pwm-dtbs := r8a779g3-sparrow-hawk.dtb r8a779g3-sparrow-hawk-fan-pwm.dtbo
 dtb-$(CONFIG_ARCH_R8A779G0) += r8a779g3-sparrow-hawk-fan-pwm.dtb
diff --git a/arch/arm64/boot/dts/renesas/r8a779g3-sparrow-hawk-fan-argon40.dtso b/arch/arm64/boot/dts/renesas/r8a779g3-sparrow-hawk-fan-argon40.dtso
new file mode 100644
index 0000000000000..c32bd665e50c4
--- /dev/null
+++ b/arch/arm64/boot/dts/renesas/r8a779g3-sparrow-hawk-fan-argon40.dtso
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+/*
+ * Device Tree Overlay for the Argon40 HAT blower fan in connector CN7
+ * on R-Car V4H ES3.0 Sparrow Hawk board
+ *
+ * Copyright (C) 2025 Marek Vasut <marek.vasut+renesas at mailbox.org>
+ *
+ * Example usage:
+ *
+ * # Localize hwmon sysfs directory that matches the PWM fan,
+ * # enable the PWM fan, and configure the fan speed manually.
+ * r8a779g3-sparrow-hawk$ ls -1 /sys/devices/platform/pwm-fan-ext/hwmon/hwmon?/pwm?_enable
+ * /sys/devices/platform/pwm-fan-ext/hwmon/hwmon0/pwm1_enable
+ *
+ * # Select mode 2 , enable fan PWM and regulator and keep them enabled.
+ * # For details, see Linux Documentation/hwmon/pwm-fan.rst
+ * r8a779g3-sparrow-hawk$ echo 2 > /sys/devices/platform/pwm-fan-ext/hwmon/hwmon0/pwm1_enable
+ *
+ * # Configure PWM fan speed in range 0..255 , 0 is stopped , 255 is full speed .
+ * # Fan speed 101 is about 2/5 of the PWM fan speed:
+ * r8a779g3-sparrow-hawk$ echo 101 > /sys/devices/platform/pwm-fan-ext/hwmon/hwmon0/pwm1
+ */
+
+/dts-v1/;
+/plugin/;
+
+&{/} {
+	pwm-fan-ext {
+		compatible = "pwm-fan";
+		#cooling-cells = <2>;
+		/* PWM period: 33us ~= 30 kHz */
+		pwms = <&pwmhat 0 33334 0>;
+		/* Available cooling levels */
+		cooling-levels = <0 50 100 150 200 255>;
+		fan-shutdown-percent = <100>;
+	};
+};
+
+/* Page 31 / IO_CN */
+&i2c3 {
+	#address-cells = <1>;
+	#size-cells = <0>;
+	clock-frequency = <400000>;
+	status = "okay";
+
+	pwmhat: pwm at 1a {
+		compatible = "argon40,fan-hat";
+		reg = <0x1a>;
+		#pwm-cells = <3>;
+	};
+};
-- 
2.51.0