linux-kernel - [PATCH 4.4 19/22] serial: 8250_dw: always set baud rate in dw8250_set

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Message-Id: <20180821055140.451598344@linuxfoundation.org>
Date:   Tue, 21 Aug 2018 08:21:45 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Chen Hu <hu1.chen@...el.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: [PATCH 4.4 19/22] serial: 8250_dw: always set baud rate in dw8250_set_termios

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Chen Hu <hu1.chen@...el.com>

commit dfcab6ba573445c703235ab6c83758eec12d7f28 upstream.

dw8250_set_termios() doesn't set baud rate if the arg "old ktermios" is
NULL. This happens during resume.
Call Trace:
...
[   54.928108] dw8250_set_termios+0x162/0x170
[   54.928114] serial8250_set_termios+0x17/0x20
[   54.928117] uart_change_speed+0x64/0x160
[   54.928119] uart_resume_port
...

So the baud rate is not restored after S3 and breaks the apps who use
UART, for example, console and bluetooth etc.

We address this issue by setting the baud rate irrespective of arg
"old", just like the drivers for other 8250 IPs. This is tested with
Intel Broxton platform.

Signed-off-by: Chen Hu <hu1.chen@...el.com>
Fixes: 4e26b134bd17 ("serial: 8250_dw: clock rate handling for all ACPI platforms")
Cc: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc: stable <stable@...r.kernel.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/tty/serial/8250/8250_dw.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -224,7 +224,7 @@ static void dw8250_set_termios(struct ua
 	unsigned int rate;
 	int ret;
 
-	if (IS_ERR(d->clk) || !old)
+	if (IS_ERR(d->clk))
 		goto out;
 
 	clk_disable_unprepare(d->clk);