From: Martin Fuzzey martin.fuzzey@flowbird.group
commit 639949a7031e04c59ec91614eceb9543e9120f43 upstream.
Since commit 79d0224f6bf2 ("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: 79d0224f6bf2 ("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.gr... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tty/serial/imx.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-)
--- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -397,6 +397,16 @@ static void start_hrtimer_ms(struct hrti hrtimer_start(hrt, ms_to_ktime(msec), HRTIMER_MODE_REL); }
+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) { @@ -418,6 +428,7 @@ static void imx_uart_start_rx(struct uar /* 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 */ @@ -1404,7 +1415,7 @@ static int imx_uart_startup(struct uart_ int retval, i; 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) @@ -1509,10 +1520,7 @@ static int imx_uart_startup(struct uart_ 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);