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serial: amba-pl011: honour delay_rts_before_send for every write

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While the driver waits out delay_rts_before_send, another write calls
pl011_start_tx() again. pl011_rs485_tx_start() then switches straight
to SEND, and the data goes out before the delay has passed.

Leave the start to the trigger_start_tx timer while it is pending.

Fixes: 2c1fd53af2 ("serial: amba-pl011: Fix RTS handling in RS485 mode")
Cc: stable@vger.kernel.org
Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
Link: https://patch.msgid.link/20261011-fix-pl011-rs485-rts-delay-v1-1-5078e61bc408@tipi-net.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Nicolai Buchwitz 2026-10-11 22:23:44 +02:00 committed by Greg Kroah-Hartman
parent 6ae994d513
commit 8a97502095
1 changed files with 7 additions and 5 deletions
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12
drivers/tty/serial/amba-pl011.c
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@ -1419,10 +1419,6 @@ static void pl011_rs485_tx_start(struct uart_amba_port *uap)
struct uart_port *port = &uap->port;
u32 cr;
if (uap->rs485_tx_state == WAIT_AFTER_RTS) {
uap->rs485_tx_state = SEND;
return;
}
if (uap->rs485_tx_state == WAIT_AFTER_SEND ||
uap->rs485_tx_state == WAIT_AFTER_SEND_DELAY) {
hrtimer_try_to_cancel(&uap->trigger_stop_tx);
@ -1461,6 +1457,10 @@ static void pl011_start_tx(struct uart_port *port)
if ((uap->port.rs485.flags & SER_RS485_ENABLED) &&
uap->rs485_tx_state != SEND) {
/* trigger_start_tx starts TX once delay_rts_before_send passed */
if (uap->rs485_tx_state == WAIT_AFTER_RTS)
return;
pl011_rs485_tx_start(uap);
if (uap->rs485_tx_state == WAIT_AFTER_RTS)
return;
@ -1477,8 +1477,10 @@ static enum hrtimer_restart pl011_trigger_start_tx(struct hrtimer *t)
unsigned long flags;
uart_port_lock_irqsave(&uap->port, &flags);
if (uap->rs485_tx_state == WAIT_AFTER_RTS)
if (uap->rs485_tx_state == WAIT_AFTER_RTS) {
uap->rs485_tx_state = SEND;
pl011_start_tx(&uap->port);
}
uart_port_unlock_irqrestore(&uap->port, flags);
return HRTIMER_NORESTART;