linux-kernel - [PATCH 4.6 075/100] serial: samsung: Reorder the sequence of clock control when call s3c24xx_serial_set

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Message-Id: <20160530204910.856855250@linuxfoundation.org>
Date:	Mon, 30 May 2016 13:50:10 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Chanwoo Choi <cw00.choi@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Subject: [PATCH 4.6 075/100] serial: samsung: Reorder the sequence of clock control when call s3c24xx_serial_set_termios()

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

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

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

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>

---
 drivers/tty/serial/samsung.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -1271,6 +1271,8 @@ static void s3c24xx_serial_set_termios(s
 	/* 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)) {
@@ -1278,8 +1280,6 @@ static void s3c24xx_serial_set_termios(s
 			ourport->baudclk = ERR_PTR(-EINVAL);
 		}
 
-		clk_prepare_enable(clk);
-
 		ourport->baudclk = clk;
 		ourport->baudclk_rate = clk ? clk_get_rate(clk) : 0;
 	}