This is a note to let you know that I've just added the patch titled
serial: core: only stop transmit when HW fifo is empty
to the 6.6-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:
serial-core-only-stop-transmit-when-hw-fifo-is-empty.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 1b150f23e95e4968ea90fd9c54e45fa724f51982
Author: Jonas Gorski <jonas.gorski@xxxxxxxxx>
Date: Sun Mar 3 16:08:07 2024 +0100
serial: core: only stop transmit when HW fifo is empty
[ Upstream commit 7bfb915a597a301abb892f620fe5c283a9fdbd77 ]
If the circular buffer is empty, it just means we fit all characters to
send into the HW fifo, but not that the hardware finished transmitting
them.
So if we immediately call stop_tx() after that, this may abort any
pending characters in the HW fifo, and cause dropped characters on the
console.
Fix this by only stopping tx when the tx HW fifo is actually empty.
Fixes: 8275b48b2780 ("tty: serial: introduce transmit helpers")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jonas Gorski <jonas.gorski@xxxxxxxxx>
Link: https://lore.kernel.org/r/20240303150807.68117-1-jonas.gorski@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 27a26092493ad..a7d5fa892be26 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -786,7 +786,8 @@ enum UART_TX_FLAGS {
if (pending < WAKEUP_CHARS) { \
uart_write_wakeup(__port); \
\
- if (!((flags) & UART_TX_NOSTOP) && pending == 0) \
+ if (!((flags) & UART_TX_NOSTOP) && pending == 0 && \
+ __port->ops->tx_empty(__port)) \
__port->ops->stop_tx(__port); \
} \
\
