6.6-stable review patch. If anyone has any objections, please let me know.
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From: Jonas Gorski jonas.gorski@gmail.com
[ 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@vger.kernel.org Signed-off-by: Jonas Gorski jonas.gorski@gmail.com Link: https://lore.kernel.org/r/20240303150807.68117-1-jonas.gorski@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/serial_core.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
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); \ } \ \