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tty: serial: fsl_lpuart: Add support for RS-485

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Enable Vybrid's build-in support for RS-485 auto RTS for controlling line
direction of RS-485 transceiver driver.

Enable RS485 feature by either using ioctrl 'TIOCSRS485' or enable it in the
device tree by setting 'linux,rs485-enabled-at-boot-time' property.

Signed-off-by: Bhuvanchandra DV <bhuvanchandra.dv@toradex.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Bhuvanchandra DV 2016-07-19 13:13:10 +05:30 committed by Greg Kroah-Hartman
parent c05efd692f
commit 03895cf41d
1 changed files with 72 additions and 6 deletions
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78
drivers/tty/serial/fsl_lpuart.c
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@ -917,6 +917,52 @@ static void lpuart_dma_rx_free(struct uart_port *port)
sport->dma_rx_cookie = -EINVAL;
}
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);
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.
*/
if (!(rs485->flags & (SER_RS485_RTS_ON_SEND |
SER_RS485_RTS_AFTER_SEND)))
rs485->flags |= SER_RS485_RTS_ON_SEND;
if (rs485->flags & SER_RS485_RTS_ON_SEND &&
rs485->flags & SER_RS485_RTS_AFTER_SEND)
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;
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)
{
unsigned int temp = 0;
@ -950,17 +996,22 @@ static unsigned int lpuart32_get_mctrl(struct uart_port *port)
static void lpuart_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
unsigned char temp;
struct lpuart_port *sport = container_of(port,
struct lpuart_port, port);
temp = readb(port->membase + UARTMODEM) &
/* Make sure RXRTSE bit is not set when RS485 is enabled */
if (!(sport->port.rs485.flags & SER_RS485_ENABLED)) {
temp = readb(sport->port.membase + UARTMODEM) &
~(UARTMODEM_RXRTSE | UARTMODEM_TXCTSE);
if (mctrl & TIOCM_RTS)
temp |= UARTMODEM_RXRTSE;
if (mctrl & TIOCM_RTS)
temp |= UARTMODEM_RXRTSE;
if (mctrl & TIOCM_CTS)
temp |= UARTMODEM_TXCTSE;
if (mctrl & TIOCM_CTS)
temp |= UARTMODEM_TXCTSE;
writeb(temp, port->membase + UARTMODEM);
writeb(temp, port->membase + UARTMODEM);
}
}
static void lpuart32_set_mctrl(struct uart_port *port, unsigned int mctrl)
@ -1256,6 +1307,13 @@ lpuart_set_termios(struct uart_port *port, struct ktermios *termios,
cr1 |= UARTCR1_M;
}
/*
* When auto RS-485 RTS mode is enabled,
* hardware flow control need to be disabled.
*/
if (sport->port.rs485.flags & SER_RS485_ENABLED)
termios->c_cflag &= ~CRTSCTS;
if (termios->c_cflag & CRTSCTS) {
modem |= (UARTMODEM_RXRTSE | UARTMODEM_TXCTSE);
} else {
@ -1870,6 +1928,8 @@ static int lpuart_probe(struct platform_device *pdev)
sport->port.ops = &lpuart_pops;
sport->port.flags = UPF_BOOT_AUTOCONF;
sport->port.rs485_config = lpuart_config_rs485;
sport->clk = devm_clk_get(&pdev->dev, "ipg");
if (IS_ERR(sport->clk)) {
ret = PTR_ERR(sport->clk);
@ -1910,6 +1970,12 @@ 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);
}
return 0;
}