linux-kernel - Re: [PATCH 7/8] serial: ar933x: Remove redundant assignment in rs485

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Date:   Sun, 26 Jun 2022 16:09:48 +0200
From:   Lino Sanfilippo <LinoSanfilippo@....de>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        vz@...ia.com, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org,
        linux-serial <linux-serial@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, lukas@...ner.de,
        p.rosenberger@...bus.com, Lino Sanfilippo <l.sanfilippo@...bus.com>
Subject: Re: [PATCH 7/8] serial: ar933x: Remove redundant assignment in
 rs485_config

On 25.06.22 at 12:14, Ilpo Järvinen wrote:
> On Wed, 22 Jun 2022, Lino Sanfilippo wrote:
>
>> From: Lino Sanfilippo <l.sanfilippo@...bus.com>
>>
>> In uart_set_rs485_config() the serial core already assigns the passed
>> serial_rs485 struct to the uart port.
>>
>> So remove the assignment in the drivers rs485_config() function to avoid
>> redundancy.
>>
>> Signed-off-by: Lino Sanfilippo <l.sanfilippo@...bus.com>
>> ---
>>  drivers/tty/serial/ar933x_uart.c | 1 -
>>  1 file changed, 1 deletion(-)
>>
>> diff --git a/drivers/tty/serial/ar933x_uart.c b/drivers/tty/serial/ar933x_uart.c
>> index ab2c5b2a1ce8..857e010d01dc 100644
>> --- a/drivers/tty/serial/ar933x_uart.c
>> +++ b/drivers/tty/serial/ar933x_uart.c
>> @@ -591,7 +591,6 @@ static int ar933x_config_rs485(struct uart_port *port,
>>  		dev_err(port->dev, "RS485 needs rts-gpio\n");
>>  		return 1;
>>  	}
>> -	port->rs485 = *rs485conf;
>>  	return 0;
>>  }
>
> Hmm, I realize that for some reason I missed cleaning up this particular
> driver after introducing the serial_rs485 sanitization. It shouldn't need
> that preceeding if block either because ar933x_no_rs485 gets applied if
> there's no rts_gpiod so the core clears SER_RS485_ENABLED.
>

I think we still need that "if" in case that RS485 was not enabled at driver
startup (no rs485-enabled-at-boot-time) and no RTS GPIO was defined but then
RS485 is enabled via TIOCSRS485.

Maybe in ar933x_uart_probe()

	if ((port->rs485.flags & SER_RS485_ENABLED) &&
	    !up->rts_gpiod) {
		dev_err(&pdev->dev, "lacking rts-gpio, disabling RS485\n");
		port->rs485.flags &= ~SER_RS485_ENABLED;
		port->rs485_supported = &ar933x_no_rs485;
	}

should rather be

	if (!up->rts_gpiod) {
		dev_err(&pdev->dev, "lacking rts-gpio, disabling RS485\n");
		port->rs485.flags &= ~SER_RS485_ENABLED;
		port->rs485_supported = &ar933x_no_rs485;
	}




Regards,
Lino