[PATCH] serial: imx: enable the clocks only when the uart is used

[PATCH] serial: imx: enable the clocks only when the uart is used

[Huang Shijie]

Current code opens the clocks when the uart driver is probed.
This will wastes some power if several uarts are enabled, but not really
used.

So close these clocks for uart, and enable the clocks only when
the uart is used.

Signed-off-by: Huang Shijie <b32955@freescale.com>
---
 drivers/tty/serial/imx.c |   12 +++++++++---
 1 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 72bc1db..5705fc8 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -699,6 +699,9 @@ static int imx_startup(struct uart_port *port)
 	int retval;
 	unsigned long flags, temp;
 
+	clk_prepare_enable(sport->clk_per);
+	clk_prepare_enable(sport->clk_ipg);
+
 	imx_setup_ufcr(sport, 0);
 
 	/* disable the DREN bit (Data Ready interrupt enable) before
@@ -884,6 +887,9 @@ static void imx_shutdown(struct uart_port *port)
 
 	writel(temp, sport->port.membase + UCR1);
 	spin_unlock_irqrestore(&sport->port.lock, flags);
+
+	clk_disable_unprepare(sport->clk_per);
+	clk_disable_unprepare(sport->clk_ipg);
 }
 
 static void
@@ -1557,6 +1563,9 @@ static int serial_imx_probe(struct platform_device *pdev)
 		goto deinit;
 	platform_set_drvdata(pdev, sport);
 
+	clk_disable_unprepare(sport->clk_per);
+	clk_disable_unprepare(sport->clk_ipg);
+
 	return 0;
 deinit:
 	if (pdata && pdata->exit)
@@ -1578,9 +1587,6 @@ static int serial_imx_remove(struct platform_device *pdev)
 
 	uart_remove_one_port(&imx_reg, &sport->port);
 
-	clk_disable_unprepare(sport->clk_per);
-	clk_disable_unprepare(sport->clk_ipg);
-
 	if (pdata && pdata->exit)
 		pdata->exit(pdev);
 
-- 
1.7.1

[PATCH] serial: imx: enable the clocks only when the uart is used

[Russell King - ARM Linux]

On Mon, Jun 03, 2013 at 03:42:11PM +0800, Huang Shijie wrote:
> Current code opens the clocks when the uart driver is probed.
> This will wastes some power if several uarts are enabled, but not really
> used.
> 
> So close these clocks for uart, and enable the clocks only when
> the uart is used.
> 
> Signed-off-by: Huang Shijie <b32955@freescale.com>
> ---
>  drivers/tty/serial/imx.c |   12 +++++++++---
>  1 files changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index 72bc1db..5705fc8 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -699,6 +699,9 @@ static int imx_startup(struct uart_port *port)
>  	int retval;
>  	unsigned long flags, temp;
>  
> +	clk_prepare_enable(sport->clk_per);
> +	clk_prepare_enable(sport->clk_ipg);

You should check the return value.  I've a good mind to mark these
functions with __must_check...

[PATCH] serial: imx: enable the clocks only when the uart is used

[Huang Shijie]

? 2013?06?03? 17:50, Russell King - ARM Linux ??:
> You should check the return value.  I've a good mind to mark these
> functions with __must_check...
yes, that's a good idea to add the __must_check.

thanks
Huang Shijie