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Subject[PATCH v1 3/3] tty: serial: lpuart: Add RS485 support for 32-bit uart flavour
Date
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>

---

drivers/tty/serial/fsl_lpuart.c | 65 ++++++++++++++++++++++++++++++++-
1 file changed, 63 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index 346b4a070ce9..22df5f8f48b6 100644
--- 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)
--
2.23.0
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