Re: [PATCH 3/3] can: c_can: Enable clock before first use

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 12/20/2012 11:05 AM, Amit Virdi wrote:
> Current implementation assumes clock to be always enabled. Instead,
> explicitly enable device clock before usage.
> 
> Signed-off-by: Amit Virdi <amit.virdi@st.com>
> Reviewed-by: Shiraz Hashim <shiraz.hashim@st.com>
> ---
>  drivers/net/can/c_can/c_can_platform.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/net/can/c_can/c_can_platform.c b/drivers/net/can/c_can/c_can_platform.c
> index 6e8dc56..d0bd6e6 100644
> --- a/drivers/net/can/c_can/c_can_platform.c
> +++ b/drivers/net/can/c_can/c_can_platform.c
> @@ -194,6 +194,12 @@ static int __devinit c_can_plat_probe(struct platform_device *pdev)
>  		goto exit;
>  	}
>  
> +	ret = clk_prepare_enable(clk);
> +	if (ret) {
> +		dev_err(&pdev->dev, "could not prepare CAN clock\n");
> +		goto exit_no_clk_en;
> +	}
> +
>  	/* get the platform data */
>  	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>  	irq = platform_get_irq(pdev, 0);
> @@ -295,6 +301,8 @@ exit_iounmap:
>  exit_release_mem:
>  	release_mem_region(mem->start, resource_size(mem));
>  exit_free_clk:
> +	clk_disable_unprepare(clk);
> +exit_no_clk_en:
>  	clk_put(clk);
>  exit:
>  	dev_err(&pdev->dev, "probe failed\n");

Why do you have to enable the clock if the driver is loaded? What about
disabling the clock on driver unload. The clock should be enabled on
open and disabled on close if the network interface. If you need to
access the registers of your hardware, you should enable the clock
before accessing the regs and disable the clock when finished.

Marc

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