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

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Date:	Thu, 27 Sep 2012 08:13:30 +0300
From:	Felipe Balbi <balbi@...com>
To:	"ABRAHAM, KISHON VIJAY" <kishon@...com>
Cc:	balbi@...com, 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

On Thu, Sep 27, 2012 at 10:43:06AM +0530, ABRAHAM, KISHON VIJAY wrote:
> 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.

then make it dev_vdbg(). It's just a debugging message, it's not saying
it will fail, it's just stating that clock isn't present and we're
trying without because it's known that some versions don't need that
clock.

Another way to do it, would be to request or not the extra clock, based
on the Revision Register (if this IP has one).

-- 
balbi

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