Re: [PATCH 2/4] doc: dt-binding: ci-hdrc-usb2: add i.mx specific binding "need-three-clocks"

[Peter Chen <peter.chen-KZfg59tc24xl57MIdRCFDg@public.gmane.org>]

On Wed, Sep 16, 2015 at 12:23:26AM -0300, Fabio Estevam wrote:
> On Tue, Sep 15, 2015 at 10:49 PM, Peter Chen <peter.chen-KZfg59tc24xl57MIdRCFDg@public.gmane.org> wrote:
> > Some SoCs needs three clock to let controller work, but others only
> > need one, add one property to differentiate this.
> >
> > Signed-off-by: Peter Chen <peter.chen-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
> > ---
> >  Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt b/Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt
> > index f15a317..4900092 100644
> > --- a/Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt
> > +++ b/Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt
> > @@ -54,6 +54,9 @@ i.mx specific properties
> >    argument that indicate usb controller index
> >  - disable-over-current: disable over current detect
> >  - external-vbus-divider: enables off-chip resistor divider for Vbus
> > +- need-three-clocks: the SoC before imx6 series (except for imx23/imx28)
> > +  needs three clcoks for controller, others only need one. Without this
> > +  property, the driver will consider this controller only need one clock.
> 
> Looking at mx31, mx35, mx25 reference manuals we see that they don't
> really need three usb clocks.
> 
> Also, if we look at the old drivers/usb/host/ehci-mxc.c we only
> require 'ipg' and 'ahb' clocks.
> 

but drivers/usb/gadget/udc/fsl_mxc_udc.c has three clocks

> So it would be better to just require these two clocks and if they are
> not found on dts, then we fall back to requesting clk_get(NULL),
> without the need of an extra property.

I considered before, but if it has clk_ipg, but without clk_ahb, do we
consider it is an error or not ? Using extra property can make things
cleaner.

-- 

Best Regards,
Peter Chen
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