[PATCH] serial/imx: enable the clock when we really use the uart port

[Huang Shijie]

The current code keeps the clock enabled even when we do not really
use the uart port. But keep the clock enabled will consume some power.

In order to save more power, disable the clock when we do not use
the uart, and enable the clock when we really use the uart port.

Signed-off-by: Huang Shijie <b32955 at freescale.com>
---
 drivers/tty/serial/imx.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index e7fecee..f5dcdf6 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -694,6 +694,8 @@ static int imx_startup(struct uart_port *port)
 	int retval;
 	unsigned long flags, temp;
 
+	clk_prepare_enable(sport->clk);
+
 	imx_setup_ufcr(sport, 0);
 
 	/* disable the DREN bit (Data Ready interrupt enable) before
@@ -877,6 +879,8 @@ static void imx_shutdown(struct uart_port *port)
 		temp &= ~(UCR1_IREN);
 
 	writel(temp, sport->port.membase + UCR1);
+
+	clk_disable_unprepare(sport->clk);
 }
 
 static void
@@ -1526,6 +1530,7 @@ static int serial_imx_probe(struct platform_device *pdev)
 		goto deinit;
 	platform_set_drvdata(pdev, &sport->port);
 
+	clk_disable_unprepare(sport->clk);
 	return 0;
 deinit:
 	if (pdata && pdata->exit)
@@ -1552,7 +1557,6 @@ static int serial_imx_remove(struct platform_device *pdev)
 
 	if (sport) {
 		uart_remove_one_port(&imx_reg, &sport->port);
-		clk_disable_unprepare(sport->clk);
 		clk_put(sport->clk);
 	}
 
-- 
1.7.3.2