linux-kernel - [PATCH 1/2] serial: 8250: Fix runtime PM for start

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Date:   Mon, 11 Apr 2022 12:48:04 +0300
From:   Tony Lindgren <tony@...mide.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Andy Shevchenko <andriy.shevchenko@...el.com>,
        Jiri Slaby <jirislaby@...nel.org>,
        Johan Hovold <johan@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-serial@...r.kernel.org, linux-omap@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Matwey V . Kornilov" <matwey@....msu.ru>,
        Steffen Trumtrar <s.trumtrar@...gutronix.de>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Subject: [PATCH 1/2] serial: 8250: Fix runtime PM for start_tx() for RS485

The early return from serial8250_start_tx() added by commit e490c9144cfa
("tty: Add software emulated RS485 support for 8250") failed to call
serial8250_rpm_put_tx() that normally gets called on __stop_tx().

Likely this is a harmless issue as the RS485 using folks probably are not
using runtime PM for the serial ports.

Fixes: e490c9144cfa ("tty: Add software emulated RS485 support for 8250")
Cc: Matwey V. Kornilov <matwey@....msu.ru>
Cc: Steffen Trumtrar <s.trumtrar@...gutronix.de>
Cc: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Signed-off-by: Tony Lindgren <tony@...mide.com>
---
 drivers/tty/serial/8250/8250_port.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1681,8 +1681,10 @@ static void serial8250_start_tx(struct uart_port *port)
 		return;
 
 	if (em485 &&
-	    em485->active_timer == &em485->start_tx_timer)
+	    em485->active_timer == &em485->start_tx_timer) {
+		serial8250_rpm_put_tx(up);
 		return;
+	}
 
 	if (em485)
 		start_tx_rs485(port);
-- 
2.35.1