On Wed, Sep 19, 2012 at 05:00:29PM +0530, Kishon Vijay Abraham I wrote:
> "usb_otg_ss_refclk960m" is needed by usb2 phy present in omap5. For
> omap4, the clk_get of this clock will fail since it does not have this
> clock.
> 
> Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
> ---
>  Documentation/devicetree/bindings/usb/usb-phy.txt |    3 +++
>  drivers/usb/phy/omap-usb2.c                       |   28 ++++++++++++++++++++-
>  2 files changed, 30 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/usb/usb-phy.txt b/Documentation/devicetree/bindings/usb/usb-phy.txt
> index 7c5fd89..d5626de 100644
> --- a/Documentation/devicetree/bindings/usb/usb-phy.txt
> +++ b/Documentation/devicetree/bindings/usb/usb-phy.txt
> @@ -24,6 +24,9 @@ Required properties:
>  add the address of control module phy power register until a driver for
>  control module is added
>  
> +Optional properties:
> + - has960mhzclk: should be added if the phy needs 960mhz clock
> +
>  This is usually a subnode of ocp2scp to which it is connected.
>  
>  usb3phy@4a084400 {
> diff --git a/drivers/usb/phy/omap-usb2.c b/drivers/usb/phy/omap-usb2.c
> index d36c282..d6612ba 100644
> --- a/drivers/usb/phy/omap-usb2.c
> +++ b/drivers/usb/phy/omap-usb2.c
> @@ -146,6 +146,7 @@ static int __devinit omap_usb2_probe(struct platform_device *pdev)
>  	struct omap_usb			*phy;
>  	struct usb_otg			*otg;
>  	struct resource			*res;
> +	struct device_node		*np = pdev->dev.of_node;
>  
>  	phy = devm_kzalloc(&pdev->dev, sizeof(*phy), GFP_KERNEL);
>  	if (!phy) {
> @@ -190,6 +191,15 @@ static int __devinit omap_usb2_probe(struct platform_device *pdev)
>  	}
>  	clk_prepare(phy->wkupclk);
>  
> +	if (of_property_read_bool(np, "has960mhzclk")) {
> +		phy->optclk = devm_clk_get(phy->dev, "usb_otg_ss_refclk960m");
> +		if (IS_ERR(phy->optclk)) {
> +			dev_err(&pdev->dev, "unable to get refclk960m\n");
> +			return PTR_ERR(phy->optclk);
> +		}
> +		clk_prepare(phy->optclk);
> +	}

instead, can't you just always try to get the clock but ignore the error
if it fails ?

If it works you can set a flag to let you know that you can use that
optional clock.

-- 
balbi