linux-kernel - Re: [PATCH 1/5] usb: dwc3: exynos: Add support for SCLK present on Exynos7

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Date:	Tue, 2 Sep 2014 12:01:02 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Vivek Gautam <gautam.vivek@...sung.com>
Cc:	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"balbi@...com" <balbi@...com>, "kishon@...com" <kishon@...com>,
	"kgene.kim@...sung.com" <kgene.kim@...sung.com>
Subject: Re: [PATCH 1/5] usb: dwc3: exynos: Add support for SCLK present on
 Exynos7

On Tue, Sep 02, 2014 at 11:39:08AM +0100, Vivek Gautam wrote:
> Hi,
> 
> 
> On Fri, Aug 29, 2014 at 12:18 AM, Mark Rutland <mark.rutland@....com> wrote:
> > On Thu, Aug 28, 2014 at 09:01:56AM +0100, Vivek Gautam wrote:
> >> Exynos7 also has a separate special gate clock going to the IP
> >> apart from the usual AHB clock. So add support for the same.
> >>
> >> Signed-off-by: Vivek Gautam <gautam.vivek@...sung.com>
> >> ---
> >>  drivers/usb/dwc3/dwc3-exynos.c |   16 ++++++++++++++++
> >>  1 file changed, 16 insertions(+)
> >>
> >> diff --git a/drivers/usb/dwc3/dwc3-exynos.c b/drivers/usb/dwc3/dwc3-exynos.c
> >> index f9fb8ad..bab6395 100644
> >> --- a/drivers/usb/dwc3/dwc3-exynos.c
> >> +++ b/drivers/usb/dwc3/dwc3-exynos.c
> >> @@ -35,6 +35,7 @@ struct dwc3_exynos {
> >>       struct device           *dev;
> >>
> >>       struct clk              *clk;
> >> +     struct clk              *sclk;
> >>       struct regulator        *vdd33;
> >>       struct regulator        *vdd10;
> >>  };
> >> @@ -141,10 +142,17 @@ static int dwc3_exynos_probe(struct platform_device *pdev)
> >>               return -EINVAL;
> >>       }
> >>
> >> +     /* Exynos7 has a special gate clock going to this IP */
> >> +     exynos->sclk = devm_clk_get(dev, "usbdrd30_sclk");
> >> +     if (IS_ERR(exynos->sclk))
> >> +             dev_warn(dev, "couldn't get sclk\n");
> >
> > Doesn't this introduce a pointless warning for Exynos SoCs other than
> > Exynos7?
> 
> True, it will introduce an unnecessary warning for non-Exynos7 systems.
> I initially thought of introducing a compatible check for Exynos7-dwc3, but that
> way we may end up adding such checks for future SoCs which have similar
> controller but have some clock difference or some other small change, no ?

Perhaps. I don't know what your future hardware will look like.

Is the usbdrd30_sclk input unique to Exynos7, or was it previously there
but just without an input?

If the latter you could just reduce this to:

dev_info(dev, "no sclk specified");

Mark.
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