From 6f12c54fa09dfd4022db1c627da42cacab2e7a24 Mon Sep 17 00:00:00 2001 From: Jonas Gorski Date: Sun, 3 Mar 2024 16:08:07 +0100 Subject: [PATCH] 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@vger.kernel.org Signed-off-by: Jonas Gorski Link: https://lore.kernel.org/r/20240303150807.68117-1-jonas.gorski@gmail.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- 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 27a26092493a..a7d5fa892be2 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); \ } \ \