linux-kernel - [PATCH 3.12 29/56] serial: samsung: Reorder the sequence of clock control when call s3c24xx_serial_set

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Message-Id: <0a10a095e60d4e3d7e8af84ff49ef63d112ce8ab.1465975780.git.jslaby@suse.cz>
Date:	Wed, 15 Jun 2016 09:30:53 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Chanwoo Choi <cw00.choi@...sung.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 29/56] serial: samsung: Reorder the sequence of clock control when call s3c24xx_serial_set_termios()

From: Chanwoo Choi <cw00.choi@...sung.com>

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

===============

commit b8995f527aac143e83d3900ff39357651ea4e0f6 upstream.

This patch fixes the broken serial log when changing the clock source
of uart device. Before disabling the original clock source, this patch
enables the new clock source to protect the clock off state for a split second.

Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com>
Reviewed-by: Marek Szyprowski <m.szyprowski@...sung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 drivers/tty/serial/samsung.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
index 6b0adfbfacaf..663508b760d8 100644
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -727,6 +727,8 @@ static void s3c24xx_serial_set_termios(struct uart_port *port,
 	/* check to see if we need  to change clock source */
 
 	if (ourport->baudclk != clk) {
+		clk_prepare_enable(clk);
+
 		s3c24xx_serial_setsource(port, clk_sel);
 
 		if (!IS_ERR(ourport->baudclk)) {
@@ -734,8 +736,6 @@ static void s3c24xx_serial_set_termios(struct uart_port *port,
 			ourport->baudclk = ERR_PTR(-EINVAL);
 		}
 
-		clk_prepare_enable(clk);
-
 		ourport->baudclk = clk;
 		ourport->baudclk_rate = clk ? clk_get_rate(clk) : 0;
 	}
-- 
2.9.0