linux-kernel - Re: [PATCH 0/2] Add software flow control support for STM32 UART

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Message-ID: <CAHp75VfDUoFMWg42OFHZtKQ972eoR3UDLVAs+BQjJm3h3-fOGw@mail.gmail.com>
Date:   Mon, 13 Apr 2020 12:17:21 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     mani@...nel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/2] Add software flow control support for STM32 UART

On Mon, Apr 13, 2020 at 7:06 AM <mani@...nel.org> wrote:
>
> From: Manivannan Sadhasivam <mani@...nel.org>
>
> Hello,
>
> This patchset adds software flow control support for STM32 UART controller.
> This is necessary for the upcoming STM32MP1 based board called Stinger96
> IoT-Box. On that board, a bluetooth chip is connected to one of the UART
> controller but the CTS/RTS lines got swapped mistakenly. So in order to
> workaround that hardware bug and also to support the usecase of using only
> Tx/Rx pins, this patchset adds software flow control support.
>
> This patchset has been validated w/ Stinger96 IoT-Box connected to Murata
> WiFi-BT combo chip.
>

I think it's a mix of terminology or so. Looking into the patches I
found that it's required to have GPIOs for SW flow control.
No, SW flow control does not require any additional signals, except RxD/TxD.

On top of that, it seems you adding mctrl-gpio functionality. Why
can't you use that one? And thus no bindings needs to be updated.

> Thanks,
> Mani
>
> Manivannan Sadhasivam (2):
>   dt-bindings: serial: Add binding for software flow control in STM32
>     UART
>   tty: serial: Add software flow control support for STM32 USART
>
>  .../bindings/serial/st,stm32-uart.yaml        |  15 +-
>  drivers/tty/serial/stm32-usart.c              | 143 +++++++++++++++++-
>  drivers/tty/serial/stm32-usart.h              |   4 +
>  3 files changed, 155 insertions(+), 7 deletions(-)
>
> --
> 2.17.1
>


-- 
With Best Regards,
Andy Shevchenko