linux-kernel - [PATCH v4 6/6] arm64: dts: rockchip: px30-ringneck-haikou: add rs485 support on uart5

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Message-Id: <20240126-dev-rx-enable-v4-6-45aaf4d96328@theobroma-systems.com>
Date: Fri, 26 Jan 2024 15:55:15 +0100
From: Farouk Bouabid <farouk.bouabid@...obroma-systems.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 Jiri Slaby <jirislaby@...nel.org>, Rob Herring <robh+dt@...nel.org>, 
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, 
 Conor Dooley <conor+dt@...nel.org>, Heiko Stuebner <heiko@...ech.de>
Cc: Rob Herring <robh@...nel.org>, linux-kernel@...r.kernel.org, 
 linux-serial@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-arm-kernel@...ts.infradead.org, linux-rockchip@...ts.infradead.org, 
 quentin.schulz@...obroma-systems.com, 
 Farouk Bouabid <farouk.bouabid@...obroma-systems.com>
Subject: [PATCH v4 6/6] arm64: dts: rockchip: px30-ringneck-haikou: add
 rs485 support on uart5

A hardware switch can set the rs485 transceiver into half or full duplex
mode.

Switching to the half-duplex mode requires the user to enable em485 on
uart5 using ioctl, DE/RE are both connected to GPIO0_B5 which is the
RTS signal for uart5. Which means GPIO0_B5 is implemented as rs485
rx-enable gpio.

In full-duplex mode (em485 is disabled), DE is connected to GPIO0_B5 and
RE is grounded (active). This requires rx-enable gpio to be inactive to
enable DE as well.

Signed-off-by: Farouk Bouabid <farouk.bouabid@...obroma-systems.com>
---
 arch/arm64/boot/dts/rockchip/px30-ringneck-haikou.dts | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/boot/dts/rockchip/px30-ringneck-haikou.dts b/arch/arm64/boot/dts/rockchip/px30-ringneck-haikou.dts
index 16798eb77077..369a6518a487 100644
--- a/arch/arm64/boot/dts/rockchip/px30-ringneck-haikou.dts
+++ b/arch/arm64/boot/dts/rockchip/px30-ringneck-haikou.dts
@@ -227,6 +227,8 @@ &uart0 {
 
 &uart5 {
 	pinctrl-0 = <&uart5_xfer>;
+	rs485-rx-enable-gpios = <&gpio0 RK_PB5 GPIO_ACTIVE_LOW>;
+	rs485-rx-enable-inactive-when-rs485-disabled;
 	status = "okay";
 };
 

-- 
2.34.1