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tty: serial: imx: fix rs485 rx after tx

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Since commit 79d0224f6b ("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: 79d0224f6b ("tty: serial: imx: Handle RS485 DE signal active high")
Cc: stable@vger.kernel.org
Signed-off-by: Martin Fuzzey <martin.fuzzey@flowbird.group>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230616104838.2729694-1-martin.fuzzey@flowbird.group
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Martin Fuzzey 2023-06-16 12:47:23 +02:00 committed by Greg Kroah-Hartman
parent e8cc334847
commit 639949a703
1 changed files with 13 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
drivers/tty/serial/imx.c
View File

@ -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);