[PATCH v5 2/6] serial: 8250: Support separate rs485 rx-enable GPIO

[Farouk Bouabid]

Hi Christoph,


On 30.01.24 13:29, Christoph Niedermaier wrote:
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>
> From: Farouk Bouabid
> Sent: Monday, January 29, 2024 9:57 AM
>
> Hi,
>
>> On 26.01.24 20:58, Lino Sanfilippo wrote:
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>>>
>>> Hi,
>>>
>>> On 26.01.24 18:27, Farouk Bouabid wrote:
>>>> From: Heiko Stuebner <heiko.stuebner at cherry.de>
>>>>
>>>> The RE signal is used to control the duplex mode of transmissions,
>>>> aka receiving data while sending in full duplex mode, while stopping
>>>> receiving data in half-duplex mode.
>>>>
>>>> On a number of boards the !RE signal is tied to ground so reception
>>>> is always enabled except if the UART allows disabling the receiver.
>>>> This can be taken advantage of to implement half-duplex mode - like
>>>> done on 8250_bcm2835aux.
>>>>
>>>> Another solution is to tie !RE to RTS always forcing half-duplex mode.
>>>>
>>>> And finally there is the option to control the RE signal separately,
>>>> like done here by introducing a new rs485-specific gpio that can be
>>>> set depending on the RX_DURING_TX setting in the common em485 callbacks.
>>>>
>>> we just added the rx_during_tx_gpio to the serial core.
>>> Why cant you use this GPIO for your purpose?
>>>
>>> Regards,
>>> Lino.
>> What we are trying to implement is a gpio that emulates the RTS signal
>> itself as we do not have a dedicated RTS signal that can be controlled
>> through MCR. The rx during tx state in our case is a fixed state of
>> "NO_RX_WHILE_TX"
> Why can't the property rts-gpios be used here for this purpose?


Yes that indeed serves our purpose. Thank you for the suggestion.


Regards

Farouk

>
>
> Regards
> Christoph