Commit 639949a7 authored by Martin Fuzzey's avatar Martin Fuzzey Committed by Greg Kroah-Hartman
Browse files

tty: serial: imx: fix rs485 rx after tx 



Since commit 79d0224f ("tty: serial: imx: Handle RS485 DE signal
active high") RS485 reception no longer works after a transmission.

The following scenario shows the problem:
	1) Open a port in RS485 mode
	2) Receive data from remote (OK)
	3) Transmit data to remote (OK)
	4) Receive data from remote (Nothing received)

In RS485 mode, imx_uart_start_tx() calls imx_uart_stop_rx() and, when the
transmission is complete, imx_uart_stop_tx() calls imx_uart_start_rx().

Since the above commit imx_uart_stop_rx() now sets the loopback bit but
imx_uart_start_rx() does not clear it causing the hardware to remain in
loopback mode and not receive external data.

Fix this by moving the existing loopback disable code to a helper function
and calling it from imx_uart_start_rx() too.

Fixes: 79d0224f ("tty: serial: imx: Handle RS485 DE signal active high")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarMartin Fuzzey <martin.fuzzey@flowbird.group>
Reviewed-by: default avatarIlpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230616104838.2729694-1-martin.fuzzey@flowbird.group


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e8cc3348

drivers/tty/serial/imx.c

+13 −5
Original line number Diff line number Diff line
@@ -369,6 +369,16 @@ static void imx_uart_soft_reset(struct imx_port *sport) 
	sport->idle_counter = 0;

}



static void imx_uart_disable_loopback_rs485(struct imx_port *sport)

{

	unsigned int uts;



	/* See SER_RS485_ENABLED/UTS_LOOP comment in imx_uart_probe() */

	uts = imx_uart_readl(sport, imx_uart_uts_reg(sport));

	uts &= ~UTS_LOOP;

	imx_uart_writel(sport, uts, imx_uart_uts_reg(sport));

}



/* called with port.lock taken and irqs off */

static void imx_uart_start_rx(struct uart_port *port)

{
@@ -390,6 +400,7 @@ static void imx_uart_start_rx(struct uart_port *port) 
	/* Write UCR2 first as it includes RXEN */

	imx_uart_writel(sport, ucr2, UCR2);

	imx_uart_writel(sport, ucr1, UCR1);

	imx_uart_disable_loopback_rs485(sport);

}



/* called with port.lock taken and irqs off */
@@ -1422,7 +1433,7 @@ static int imx_uart_startup(struct uart_port *port) 
	int retval;

	unsigned long flags;

	int dma_is_inited = 0;

	u32 ucr1, ucr2, ucr3, ucr4, uts;

	u32 ucr1, ucr2, ucr3, ucr4;



	retval = clk_prepare_enable(sport->clk_per);

	if (retval)
@@ -1521,10 +1532,7 @@ static int imx_uart_startup(struct uart_port *port) 
		imx_uart_writel(sport, ucr2, UCR2);

	}



	/* See SER_RS485_ENABLED/UTS_LOOP comment in imx_uart_probe() */

	uts = imx_uart_readl(sport, imx_uart_uts_reg(sport));

	uts &= ~UTS_LOOP;

	imx_uart_writel(sport, uts, imx_uart_uts_reg(sport));

	imx_uart_disable_loopback_rs485(sport);



	spin_unlock_irqrestore(&sport->port.lock, flags);