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Subject: Re: [PATCH 1/4] serial: 8250_dw: add em485 support
To:     Andy Shevchenko <andy.shevchenko@gmail.com>
Cc:     "Matwey V. Kornilov" <matwey.kornilov@gmail.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jslaby@suse.com>, Ed Blake <ed.blake@sondrel.com>,
        Joshua Scott <joshua.scott@alliedtelesis.co.nz>,
        "open list:SERIAL DRIVERS" <linux-serial@vger.kernel.org>,
        open list <linux-kernel@vger.kernel.org>
References: <CAJs94EZqdQAQG+inWvj89FCQtv06LxhY_J4YgNmK8mtvgDTchQ@mail.gmail.com>
 <20180606095156.72628-1-giulio.benetti@micronovasrl.com>
 <20180606095156.72628-4-giulio.benetti@micronovasrl.com>
 <CAHp75VfgYmX5WiG5HpN7hLiW1CfhDYV2gya58OGYyBQwVGTY2A@mail.gmail.com>
From:   Giulio Benetti <giulio.benetti@micronovasrl.com>
Message-ID: <9d8bdd5b-842f-8943-a186-a99f31d71a2a@micronovasrl.com>
Date:   Wed, 6 Jun 2018 21:16:37 +0200
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Il 06/06/2018 18:51, Andy Shevchenko ha scritto:
> On Wed, Jun 6, 2018 at 12:51 PM, Giulio Benetti
> <giulio.benetti@micronovasrl.com> wrote:
>> Need to use rs485 transceiver so let's use existing em485 485 emulation
>> layer on top of 8250.
>>
>> Add rs485_config callback to port.
> 
> Besides the fact the series lacks of cover letter, I think it should

Sorry for that, next patchsets will have cover-letters.

> be postponed until we get a clear understanding how RS485 is supposed
> to be initialized and what exact problems you are trying to address.
> 
>>
>> Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
>> ---
>>   drivers/tty/serial/8250/8250_dw.c | 31 +++++++++++++++++++++++++++++++
>>   1 file changed, 31 insertions(+)
>>
>> diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
>> index 6fcdb90f616a..45366e6e5411 100644
>> --- a/drivers/tty/serial/8250/8250_dw.c
>> +++ b/drivers/tty/serial/8250/8250_dw.c
>> @@ -314,6 +314,36 @@ static void dw8250_set_ldisc(struct uart_port *p, struct ktermios *termios)
>>          serial8250_do_set_ldisc(p, termios);
>>   }
>>
>> +static int dw8250_rs485_config(struct uart_port *p,
>> +                              struct serial_rs485 *rs485)
>> +{
>> +       struct uart_8250_port *up = up_to_u8250p(p);
>> +
>> +       /* Clamp the delays to [0, 100ms] */
>> +       rs485->delay_rts_before_send = min(rs485->delay_rts_before_send, 100U);
>> +       rs485->delay_rts_after_send  = min(rs485->delay_rts_after_send, 100U);
>> +
>> +       p->rs485 = *rs485;
>> +
>> +       /*
>> +        * Both serial8250_em485_init and serial8250_em485_destroy
>> +        * are idempotent
>> +        */
>> +       if (rs485->flags & SER_RS485_ENABLED) {
>> +               int ret = serial8250_em485_init(up);
>> +
>> +               if (ret) {
>> +                       rs485->flags &= ~SER_RS485_ENABLED;
>> +                       p->rs485.flags &= ~SER_RS485_ENABLED;
>> +               }
>> +               return ret;
>> +       }
>> +
>> +       serial8250_em485_destroy(up);
>> +
>> +       return 0;
>> +}
>> +
>>   /*
>>    * dw8250_fallback_dma_filter will prevent the UART from getting just any free
>>    * channel on platforms that have DMA engines, but don't have any channels
>> @@ -449,6 +479,7 @@ static int dw8250_probe(struct platform_device *pdev)
>>          p->serial_out   = dw8250_serial_out;
>>          p->set_ldisc    = dw8250_set_ldisc;
>>          p->set_termios  = dw8250_set_termios;
>> +       p->rs485_config = dw8250_rs485_config;
>>
>>          p->membase = devm_ioremap(dev, regs->start, resource_size(regs));
>>          if (!p->membase)
>> --
>> 2.17.1
>>
> 
> 
> 

-- 
Giulio Benetti
CTO

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