linux-kernel - Re: [PATCH v4 5/9] usb: dwc3: Rework clock initialization to be more flexible

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Message-ID: <CALAqxLXcD8V1o01yMrHpeoqU2MfJ=8d3dbzC8T-+aoovDUd8kA@mail.gmail.com>
Date:   Tue, 29 Oct 2019 09:08:53 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     Felipe Balbi <balbi@...nel.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        ShuFan Lee <shufan_lee@...htek.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Yu Chen <chenyu56@...wei.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Jun Li <lijun.kernel@...il.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Jack Pham <jackp@...eaurora.org>,
        Linux USB List <linux-usb@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH v4 5/9] usb: dwc3: Rework clock initialization to be more flexible

On Tue, Oct 29, 2019 at 2:14 AM Felipe Balbi <balbi@...nel.org> wrote:
> John Stultz <john.stultz@...aro.org> writes:
>
> > The dwc3 core binding specifies three clocks:
> >   ref, bus_early, and suspend
> >
> > which are all controlled in the driver together.
> >
> > However some variants of the hardware my not have all three clks
>                                         ^^
>                                         may
>
> In fact *all* platforms have all three clocks. It's just that in some
> cases clock pins are shorted together (or take input from same clock).
>
...
> another option would be to pass three clocks with the same phandle. That
> would even make sure that clock usage counts are correct, no?

Hey Felipe!

So I actually had done that initially (and it seemed to work), but Rob
suggested this way instead.
I'm fine with either, as long as having multiple references to the
same clk in the enable/disable paths doesn't cause trouble.

Thanks so much for the review here!
-john