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SubjectRe: [PATCH 3/3] tty: serial: fsl_lpuart: Add support for RS-485
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 <bhuvanchandra.dv@toradex.com>
> ---
> 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.

> + 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.

> + 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).

> + 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->)

> + 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.

> + 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.



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