linux-kernel - [PATCH v4 3/6] dt-bindings: serial: add binding for rs485 rx-enable state when rs485 is disabled

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Message-Id: <20240126-dev-rx-enable-v4-3-45aaf4d96328@theobroma-systems.com>
Date: Fri, 26 Jan 2024 15:55:12 +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 3/6] dt-bindings: serial: add binding for rs485
 rx-enable state when rs485 is disabled

RS485 can have a receiver-enable gpio (rx-enable-gpios). When rs485 is
enabled, this gpio, if provided, must be driven active while receiving.
However when RS485 is disabled this gpio should not have an undefined
state. In that case, as DE and RE pins can be connected both to this gpio,
if its state is not properly defined, can cause unexpected transceiver
behavior.
This binding depend on rx-enable-gpios to be implemented.

Signed-off-by: Farouk Bouabid <farouk.bouabid@...obroma-systems.com>
---
 Documentation/devicetree/bindings/serial/rs485.yaml | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/devicetree/bindings/serial/rs485.yaml b/Documentation/devicetree/bindings/serial/rs485.yaml
index b64577036b5c..4c79dfaaf460 100644
--- a/Documentation/devicetree/bindings/serial/rs485.yaml
+++ b/Documentation/devicetree/bindings/serial/rs485.yaml
@@ -55,6 +55,11 @@ properties:
     description: GPIO to handle a separate RS485 receive enable signal
     maxItems: 1
 
+  rs485-rx-enable-inactive-when-rs485-disabled:
+    description: rx-enable GPIO is not active when RS485 is disabled. If missing, active-state
+      is assumed.
+    $ref: /schemas/types.yaml#/definitions/flag
+
   rs485-term-gpios:
     description: GPIO pin to enable RS485 bus termination.
     maxItems: 1

-- 
2.34.1