6.6-stable review patch. If anyone has any objections, please let me know.
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From: Paul Geurts paul_geurts@live.nl
[ Upstream commit 78d60dae9a0c9f09aa3d6477c94047df2fe6f7b0 ]
When using the serial port as RS485 port, the tx statemachine is used to control the RTS pin to drive the RS485 transceiver TX_EN pin. When the TTY port is closed in the middle of a transmission (for instance during userland application crash), imx_uart_shutdown disables the interface and disables the Transmission Complete interrupt. afer that, imx_uart_stop_tx bails on an incomplete transmission, to be retriggered by the TC interrupt. This interrupt is disabled and therefore the tx statemachine never transitions out of SEND. The statemachine is in deadlock now, and the TX_EN remains low, making the interface useless.
imx_uart_stop_tx now checks for incomplete transmission AND whether TC interrupts are enabled before bailing to be retriggered. This makes sure the state machine handling is reached, and is properly set to WAIT_AFTER_SEND.
Fixes: cb1a60923609 ("serial: imx: implement rts delaying for rs485") Signed-off-by: Paul Geurts paul_geurts@live.nl Tested-by: Rasmus Villemoes rasmus.villemoes@prevas.dk Tested-by: Eberhard Stoll eberhard.stoll@gmx.de Link: https://lore.kernel.org/r/AM0PR09MB26758F651BC1B742EB45775995B8A@AM0PR09MB26... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/tty/serial/imx.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 2e85c77e7c0d..c084ac3bb441 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -421,13 +421,13 @@ static void imx_uart_stop_tx(struct uart_port *port) ucr1 = imx_uart_readl(sport, UCR1); imx_uart_writel(sport, ucr1 & ~UCR1_TRDYEN, UCR1);
+ ucr4 = imx_uart_readl(sport, UCR4); usr2 = imx_uart_readl(sport, USR2); - if (!(usr2 & USR2_TXDC)) { + if ((!(usr2 & USR2_TXDC)) && (ucr4 & UCR4_TCEN)) { /* The shifter is still busy, so retry once TC triggers */ return; }
- ucr4 = imx_uart_readl(sport, UCR4); ucr4 &= ~UCR4_TCEN; imx_uart_writel(sport, ucr4, UCR4);