Subject: [PATCH 3/3] tty: serial: fsl_lpuart: Add support for RS-485

From: [email-masked] (Bhuvanchandra DV)
Date: Fri, 29 May 2015 16:12:13 +0530

On 05/29/2015 03:48 PM, Jakub Kici?ski wrote:
> On Fri, 29 May 2015 13:35:54 +0530, Bhuvanchandra DV wrote:
>> Enable Vybrid's build-in support for RS-485 auto RTS for
>> controlling line direction of RS-485 transceiver driver.
>>
>> Signed-off-by: Bhuvanchandra DV <[email-masked]>
>> ---
>>   drivers/tty/serial/fsl_lpuart.c | 60 +++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 60 insertions(+)
>>
>> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
>> index 357f623..c553b14 100644
>> --- a/drivers/tty/serial/fsl_lpuart.c
>> +++ b/drivers/tty/serial/fsl_lpuart.c
>> @@ -820,6 +820,50 @@ static unsigned int lpuart32_tx_empty(struct uart_port *port)
>>   		TIOCSER_TEMT : 0;
>>   }
>>
>> +static int lpuart_config_rs485(struct uart_port *port,
>> +			struct serial_rs485 *rs485)
>> +{
>> +	struct lpuart_port *sport = container_of(port,
>> +			struct lpuart_port, port);
>> +	u8 modem = readb(sport->port.membase + UARTMODEM) &
>> +		~(UARTMODEM_TXRTSPOL | UARTMODEM_TXRTSE);
>
> Please put empty line between variables and code.
Ok
>
>> +	writeb(modem, sport->port.membase + UARTMODEM);
>> +
>> +	if (rs485->flags & SER_RS485_ENABLED) {
>> +		/* Enable auto RS-485 RTS mode */
>> +		modem |= UARTMODEM_TXRTSE;
>> +
>> +		/*
>> +		* RTS needs to be logic HIGH either during transer _or_ after
>> +		* transfer, other variants are not supported by the hardware.
>> +		*/
>
> Indentation is off here.  '*' should be aligned.
Ok
>
>> +		if (!(rs485->flags & (SER_RS485_RTS_ON_SEND |
>> +				SER_RS485_RTS_AFTER_SEND)))
>
> and here - things should be aligned on the containing bracket (SER_
> under SER_ here).
Ok
>
>> +			rs485->flags |= SER_RS485_RTS_ON_SEND;
>> +
>> +		if (rs485->flags & SER_RS485_RTS_ON_SEND &&
>> +				rs485->flags & SER_RS485_RTS_AFTER_SEND)
>
> and here - same bracket rule (rs485-> under rs485->)
Ok
>
>> +			rs485->flags &= ~SER_RS485_RTS_AFTER_SEND;
>> +
>> +		/*
>> +		* The hardware defaults to RTS logic HIGH while transfer.
>> +		* Switch polarity in case RTS shall be logic HIGH
>> +		* after transfer.
>> +		* Note: UART is assumed to be active high.
>> +		*/
>> +		if (rs485->flags & SER_RS485_RTS_ON_SEND)
>> +			modem &= ~UARTMODEM_TXRTSPOL;
>
> UARTMODEM_TXRTSPOL was already clear when you read modem.
Ok
>
>> +		else if (rs485->flags & SER_RS485_RTS_AFTER_SEND)
>> +			modem |= UARTMODEM_TXRTSPOL;
>> +	}
>> +
>> +	/* Store the new configuration */
>> +	sport->port.rs485 = *rs485;
>> +
>> +	writeb(modem, sport->port.membase + UARTMODEM);
>> +	return 0;
>> +}
>> +
>>   static unsigned int lpuart_get_mctrl(struct uart_port *port)
>>   {
>>   	return TIOCM_CAR | TIOCM_CTS | TIOCM_DSR;
> [...]
>> @@ -1802,6 +1854,14 @@ static int lpuart_probe(struct platform_device *pdev)
>>   		dev_info(sport->port.dev, "DMA rx channel request failed, "
>>   				"operating without rx DMA\n");
>>
>> +	if (of_property_read_bool(np, "linux,rs485-enabled-at-boot-time")) {
>> +		sport->port.rs485.flags |= SER_RS485_ENABLED;
>> +		sport->port.rs485.flags |= SER_RS485_RTS_ON_SEND;
>> +		writeb(UARTMODEM_TXRTSE, sport->port.membase + UARTMODEM);
>> +	} else {
>> +		sport->port.rs485.flags &= ~SER_RS485_ENABLED;
>
> Why the need to clear the flag?  sport was kzalloc'ed.
Will remove it.

Best Regards,
Bhuvan