linux-kernel - [PATCH v4 5/6] arm64: dts: rockchip: rk3399-puma-haikou: add rs485 support on uart2

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Message-Id: <20240126-dev-rx-enable-v4-5-45aaf4d96328@theobroma-systems.com>
Date: Fri, 26 Jan 2024 15:55:14 +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 5/6] arm64: dts: rockchip: rk3399-puma-haikou: add rs485
 support on uart2

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
uart2 using ioctl, DE/RE are both connected to GPIO2_C3 which is the
RTS signal for uart0. Which means GPIO2_C3 is implemented as rs485
rx-enable gpio.

In full-duplex mode (em485 is disabled), DE is connected to GPIO2_C3 and
RE is grounded (enabled). 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/rk3399-puma-haikou.dts | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/boot/dts/rockchip/rk3399-puma-haikou.dts b/arch/arm64/boot/dts/rockchip/rk3399-puma-haikou.dts
index 18a98c4648ea..576024c745ed 100644
--- a/arch/arm64/boot/dts/rockchip/rk3399-puma-haikou.dts
+++ b/arch/arm64/boot/dts/rockchip/rk3399-puma-haikou.dts
@@ -273,11 +273,13 @@ &u2phy0_host {
 
 &uart0 {
 	pinctrl-names = "default";
-	pinctrl-0 = <&uart0_xfer &uart0_cts &uart0_rts>;
+	pinctrl-0 = <&uart0_xfer>;
 	status = "okay";
 };
 
 &uart2 {
+	rs485-rx-enable-gpios = <&gpio2 RK_PC3 GPIO_ACTIVE_LOW>;
+	rs485-rx-enable-inactive-when-rs485-disabled;
 	status = "okay";
 };
 

-- 
2.34.1