linux-kernel - Re: [PATCH v3 5/5] serial: 8250

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Message-ID: <9b2a7c4c-2ef1-5198-9aae-83f9fec00289@micronovasrl.com>
Date:   Fri, 5 Feb 2021 18:46:56 +0100
From:   Giulio Benetti <giulio.benetti@...ronovasrl.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Heiko Stuebner <heiko@...ech.de>, gregkh@...uxfoundation.org,
        jslaby@...e.com, matwey.kornilov@...il.com, lukas@...ner.de,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        christoph.muellner@...obroma-systems.com,
        Heiko Stuebner <heiko.stuebner@...obroma-systems.com>
Subject: Re: [PATCH v3 5/5] serial: 8250_dw: add em485 support

Il 02/02/2021 12:22, Andy Shevchenko ha scritto:
> On Tue, Feb 02, 2021 at 01:31:17AM +0100, Giulio Benetti wrote:
>> Il 18/05/2020 17:21, Andy Shevchenko ha scritto:
>>> On Sun, May 17, 2020 at 11:56:10PM +0200, Heiko Stuebner wrote:
>>>> From: Giulio Benetti <giulio.benetti@...ronovasrl.com>
>>>>
>>>> Need to use rs485 transceiver so let's use existing em485 485 emulation
>>>> layer on top of 8250.
>>>>
>>>> Add rs485_config callback to port and uses the standard em485 start and
>>>> stop helpers.
>>>
>>> Would it prevent to use native RS485 support?
>>
>> 8250_dw doesn't have a native RS485 support, do you mean using hardware
>> RTS assertion? Anyway at the moment it's not present. This would be the
>> first rs485 support added to 8250_dw.
> 
> DW v4.0+ has it.

I have access to datasheet of DW v3, and I don't have access to hardware
with DW v4.0v Uart.
But I could add rs485emu for only UART version < 4.0 and I can find Uart
version by reading UCV register, would it be acceptable?

Best regards
-- 
Giulio Benetti
CTO

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