serial: amba-pl011: keep transmitter enabled when disabling RS485

Disabling RS485 on an open port calls pl011_rs485_tx_stop(), which
turns off the transmitter. Only the RS485 TX path turns it back on, so
any later output stays queued and tcdrain() hangs until the port is
closed.

pl011_rs485_tx_stop() also checks only the hardware FIFO. If a DMA
transfer has started but has not filled the FIFO yet, the transmitter
is turned off under the transfer and the DMA channel never recovers.

When leaving RS485 mode, cancel pending deferred starts and stops, leave
the transmitter enabled and start any TX that was still waiting for
delay_rts_before_send.

Fixes: 8d479237727c ("serial: amba-pl011: add RS485 support")
Cc: stable@kernel.org
Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
Link: https://patch.msgid.link/20261012-fix-pl011-rs485-txe-v2-1-e9bf7d218389@tipi-net.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

0 files changed, 0 insertions, 0 deletions