linux-kernel - Re: [PATCH 4/4] usb: phy: omap-usb2: enable 960Mhz clock for omap5

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Date:	Thu, 27 Sep 2012 10:43:06 +0530
From:	"ABRAHAM, KISHON VIJAY" <kishon@...com>
To:	balbi@...com
Cc:	grant.likely@...retlab.ca, rob.herring@...xeda.com,
	rob@...dley.net, linux@....linux.org.uk, linux-usb@...r.kernel.org,
	linux-omap@...r.kernel.org, devicetree-discuss@...ts.ozlabs.org,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 4/4] usb: phy: omap-usb2: enable 960Mhz clock for omap5

Hi,

On Wed, Sep 26, 2012 at 11:57 PM, Felipe Balbi <balbi@...com> wrote:
> Hi,
>
> On Wed, Sep 26, 2012 at 11:10:48AM +0530, ABRAHAM, KISHON VIJAY wrote:
>> Hi,
>>
>> On Wed, Sep 19, 2012 at 5:26 PM, Felipe Balbi <balbi@...com> wrote:
>> > 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@...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@...84400 {
>> >> 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 ?
>>
>> This clock is needed for usb2 to work in dwc3 (omap5). So we have to
>> report the error in case we dont get the clock no?
>
> sure, but you don't need to bail out. Print a warning message such as:
>
> dev_dbg(&pdev->dev, "couldn't get refclk960m, trying without\n");

but then we'll get this debug message for omap4 which actually doesn't
need 960m clk.

Thanks
Kishon
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