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[v5,3/6] dt-bindings: serial: add binding for rs485 rx-enable state when rs485 is disabled

Message ID 20240126-dev-rx-enable-v5-3-5d934eda05ca@theobroma-systems.com
State New
Headers show
Series [v5,1/6] dt-bindings: serial: Add binding for rs485 receiver enable GPIO | expand

Commit Message

Farouk Bouabid Jan. 26, 2024, 5:27 p.m. UTC
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@theobroma-systems.com>
---
 Documentation/devicetree/bindings/serial/rs485.yaml | 5 +++++
 1 file changed, 5 insertions(+)

Comments

Rob Herring (Arm) Jan. 30, 2024, 11:02 p.m. UTC | #1
On Fri, Jan 26, 2024 at 06:27:44PM +0100, Farouk Bouabid wrote:
> RS485 can have a receiver-enable gpio (rx-enable-gpios). When rs485 is

s/gpio/GPIO/

> 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.

Sounds like a constraint:

dependencies:
  rs485-rx-enable-inactive-when-rs485-disabled: [ rx-enable-gpios ]

> 
> Signed-off-by: Farouk Bouabid <farouk.bouabid@theobroma-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:

For something a bit shorter, perhaps: rs485-rx-enable-inactive-on-disable

> +    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
>
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Patch

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