linux-kernel - [PATCH v2 1/2] serial: core: preserve cflags, ispeed and ospeed

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Date:   Wed,  5 Apr 2023 13:15:58 +0200
From:   Lukasz Majczak <lma@...ihalf.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>
Cc:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        upstream@...ihalf.com, Lukasz Majczak <lma@...ihalf.com>,
        stable@...r.kernel.org
Subject: [PATCH v2 1/2] serial: core: preserve cflags, ispeed and ospeed

Re-enable the console device after suspending, causes its cflags,
ispeed and ospeed to be set anew, basing on the values stored in
uport->cons. These values are set only once,
when parsing console parameters after boot (see uart_set_options()),
next after configuring a port in uart_port_startup() these parameters
(cflags, ispeed and ospeed) are copied to termios structure and
the original one (stored in uport->cons) are cleared, but there is no place
in code where those fields are checked against 0.
When kernel calls uart_resume_port() and setups console, it copies cflags,
ispeed and ospeed values from uart->cons, but those are already cleared.
The effect is that the console is broken.
This patch address the issue by preserving the cflags, ispeed and
ospeed fields in uart->cons during uart_port_startup().

Signed-off-by: Lukasz Majczak <lma@...ihalf.com>
Cc: <stable@...r.kernel.org> # 4.14+
---
 drivers/tty/serial/serial_core.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 2bd32c8ece39..394a05c09d87 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -225,9 +225,6 @@ static int uart_port_startup(struct tty_struct *tty, struct uart_state *state,
 			tty->termios.c_cflag = uport->cons->cflag;
 			tty->termios.c_ispeed = uport->cons->ispeed;
 			tty->termios.c_ospeed = uport->cons->ospeed;
-			uport->cons->cflag = 0;
-			uport->cons->ispeed = 0;
-			uport->cons->ospeed = 0;
 		}
 		/*
 		 * Initialise the hardware port settings.
-- 
2.40.0.577.gac1e443424-goog