linux-kernel - [PATCH v6 2/2] arm64: dts: rockchip: px30-ringneck-haikou: add rs485 support on uart5

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Message-Id: <20240208-dev-rx-enable-v6-2-39e68e17a339@theobroma-systems.com>
Date: Thu, 08 Feb 2024 16:39:56 +0100
From: Farouk Bouabid <farouk.bouabid@...obroma-systems.com>
To: 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: devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
 linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 quentin.schulz@...obroma-systems.com, 
 Farouk Bouabid <farouk.bouabid@...obroma-systems.com>
Subject: [PATCH v6 2/2] 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 uart0. Implement GPIO0_B5 as rts-gpios with RTS_ON_SEND
option enabled (default) so that driver mode gets enabled while sending
(RTS high) and receiver mode gets enabled while not sending (RTS low).

In full-duplex mode (em485 is disabled), DE is connected to GPIO0_B5 and
RE is grounded (enabled). Since GPIO0_B5 is implemented as rts-gpios, the
driver mode gets enabled whenever we want to send something and RE is not
affected (always enabled) in this case by the state of RTS.

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

diff --git a/arch/arm64/boot/dts/rockchip/px30-ringneck-haikou.dts b/arch/arm64/boot/dts/rockchip/px30-ringneck-haikou.dts
index 16798eb77077..ae398acdcf45 100644
--- a/arch/arm64/boot/dts/rockchip/px30-ringneck-haikou.dts
+++ b/arch/arm64/boot/dts/rockchip/px30-ringneck-haikou.dts
@@ -227,6 +227,7 @@ &uart0 {

 &uart5 {
 	pinctrl-0 = <&uart5_xfer>;
+	rts-gpios = <&gpio0 RK_PB5 GPIO_ACTIVE_HIGH>;
 	status = "okay";
 };

-- 
2.34.1