linux-kernel - Re: [PATCH 4/7] dt_bindings: snps-dw-apb-uart: Add RS485

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Date:   Wed, 2 Mar 2022 11:47:13 -0600
From:   Rob Herring <robh@...nel.org>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     linux-serial@...r.kernel.org, Jiri Slaby <jirislaby@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, Lukas Wunner <lukas@...ner.de>,
        Johan Hovold <johan@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 4/7] dt_bindings: snps-dw-apb-uart: Add RS485

On Wed, Mar 02, 2022 at 11:56:03AM +0200, Ilpo Järvinen wrote:
> Add RS485 enable & line polarity properties.
> 
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: devicetree@...r.kernel.org
> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> ---
>  .../bindings/serial/snps-dw-apb-uart.yaml       | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
> index 12137fe80acf..8d440afabb1f 100644
> --- a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
> +++ b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.yaml
> @@ -103,6 +103,23 @@ properties:
>        register. Define this if your serial port does not use this pin.
>      type: boolean
>  
> +  snps,rs485-interface-en:
> +    description: Use true RS-485 DE and RE signals (in contrast to RS-485
> +      emulation using RTS). Requires IP version 4 or above.
> +    type: boolean
> +

> +  snps,de-active-high:
> +    description: Defines the polarity of driver enable (DE_EN) signal.
> +      Meaningful only with snps,rs485-interface-en. True indicates active
> +      high.
> +    type: boolean
> +
> +  snps,re-active-high:
> +    description: Defines the polarity of receiver enable (RE_EN) signal.
> +      Meaningful only with snps,rs485-interface-en. True indicates active
> +      high.
> +    type: boolean

Seems plausible that other rs485 implementations could have varying 
polarities too. IOW, should be common properties.

> +
>  required:
>    - compatible
>    - reg
> -- 
> 2.30.2
>