This is a note to let you know that I've just added the patch titled
tty: serial: imx: fix rs485 rx after tx
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tty-serial-imx-fix-rs485-rx-after-tx.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 639949a7031e04c59ec91614eceb9543e9120f43 Mon Sep 17 00:00:00 2001
From: Martin Fuzzey <martin.fuzzey@flowbird.group>
Date: Fri, 16 Jun 2023 12:47:23 +0200
Subject: tty: serial: imx: fix rs485 rx after tx
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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@xxxxxxxxxxxxxxx
Signed-off-by: Martin Fuzzey <martin.fuzzey@flowbird.group>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20230616104838.2729694-1-martin.fuzzey@flowbird.group
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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 */
@@ -1394,7 +1405,7 @@ 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)
@@ -1499,10 +1510,7 @@ 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);
Patches currently in stable-queue which might be from martin.fuzzey@flowbird.group are
queue-5.15/tty-serial-imx-fix-rs485-rx-after-tx.patch
