linux-kernel - [PATCH 5.10 212/238] tty: serial: samsung: fix tx_empty() to return TIOCSER

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Date: Sun, 24 Mar 2024 19:40:00 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Tudor Ambarus <tudor.ambarus@...aro.org>,
	Sam Protsenko <semen.protsenko@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.10 212/238] tty: serial: samsung: fix tx_empty() to return TIOCSER_TEMT

From: Tudor Ambarus <tudor.ambarus@...aro.org>

[ Upstream commit 314c2b399288f0058a8c5b6683292cbde5f1531b ]

The core expects for tx_empty() either TIOCSER_TEMT when the tx is
empty or 0 otherwise. s3c24xx_serial_txempty_nofifo() might return
0x4, and at least uart_get_lsr_info() tries to clear exactly
TIOCSER_TEMT (BIT(1)). Fix tx_empty() to return TIOCSER_TEMT.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Tudor Ambarus <tudor.ambarus@...aro.org>
Reviewed-by: Sam Protsenko <semen.protsenko@...aro.org>
Link: https://lore.kernel.org/r/20240119104526.1221243-2-tudor.ambarus@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/tty/serial/samsung_tty.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
index fa5b1321d9b15..5388eb7fa0f47 100644
--- a/drivers/tty/serial/samsung_tty.c
+++ b/drivers/tty/serial/samsung_tty.c
@@ -922,11 +922,10 @@ static unsigned int s3c24xx_serial_tx_empty(struct uart_port *port)
 		if ((ufstat & info->tx_fifomask) != 0 ||
 		    (ufstat & info->tx_fifofull))
 			return 0;
-
-		return 1;
+		return TIOCSER_TEMT;
 	}
 
-	return s3c24xx_serial_txempty_nofifo(port);
+	return s3c24xx_serial_txempty_nofifo(port) ? TIOCSER_TEMT : 0;
 }
 
 /* no modem control lines */
-- 
2.43.0