From 7bfb915a597a301abb892f620fe5c283a9fdbd77 Mon Sep 17 00:00:00 2001
From: Jonas Gorski <jonas.gorski@gmail.com>
Date: Sun, 3 Mar 2024 16:08:07 +0100
Subject: [PATCH] serial: core: only stop transmit when HW fifo is empty
Git-commit: 7bfb915a597a301abb892f620fe5c283a9fdbd77
Patch-mainline: v6.9-rc1
References: git-fixes
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>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
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 55b1f3ba48ac..bb0f2d4ac62f 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); \
} \
\
--
2.43.0