tty: serial: lpuart: Add RS485 support for 32-bit uart flavour

This commits adds RS485 support for LPUART hardware that uses 32-bit
registers. These are typically found in i.MX8 processors.

Signed-off-by: Philippe Schenker <philippe.schenker@toradex.com>
Reviewed-by: Fugang Duan <fugang.duan@nxp.com>
Link: https://lore.kernel.org/r/20191017141428.10330-3-philippe.schenker@toradex.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 346b4a070ce9881a757716eb85c357bee12cbf24..22df5f8f48b6ec3578525d2bcd60c0fd909eef73 100644 (file)
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -1280,6 +1280,57 @@ static int lpuart_config_rs485(struct uart_port *port,
        return 0;
 }
 
+static int lpuart32_config_rs485(struct uart_port *port,
+                       struct serial_rs485 *rs485)
+{
+       struct lpuart_port *sport = container_of(port,
+                       struct lpuart_port, port);
+
+       unsigned long modem = lpuart32_read(&sport->port, UARTMODIR)
+                               & ~(UARTMODEM_TXRTSPOL | UARTMODEM_TXRTSE);
+       lpuart32_write(&sport->port, modem, UARTMODIR);
+
+       /* clear unsupported configurations */
+       rs485->delay_rts_before_send = 0;
+       rs485->delay_rts_after_send = 0;
+       rs485->flags &= ~SER_RS485_RX_DURING_TX;
+
+       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;
+
+       lpuart32_write(&sport->port, modem, UARTMODIR);
+       return 0;
+}
+
 static unsigned int lpuart_get_mctrl(struct uart_port *port)
 {
        unsigned int temp = 0;
@@ -1878,6 +1929,13 @@ lpuart32_set_termios(struct uart_port *port, struct ktermios *termios,
                ctrl |= UARTCTRL_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 |= (UARTMODIR_RXRTSE | UARTMODIR_TXCTSE);
        } else {
@@ -2405,7 +2463,10 @@ 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;
+       if (lpuart_is_32(sport))
+               sport->port.rs485_config = lpuart32_config_rs485;
+       else
+               sport->port.rs485_config = lpuart_config_rs485;
 
        sport->ipg_clk = devm_clk_get(&pdev->dev, "ipg");
        if (IS_ERR(sport->ipg_clk)) {
@@ -2459,7 +2520,7 @@ static int lpuart_probe(struct platform_device *pdev)
            sport->port.rs485.delay_rts_after_send)
                dev_err(&pdev->dev, "driver doesn't support RTS delays\n");
 
-       lpuart_config_rs485(&sport->port, &sport->port.rs485);
+       sport->port.rs485_config(&sport->port, &sport->port.rs485);
 
        sport->dma_tx_chan = dma_request_slave_channel(sport->port.dev, "tx");
        if (!sport->dma_tx_chan)