linux-kernel - Re: [PATCH 4/5] dt-bindings: usb: dwc3: of-simple: add compatible for HiSi

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Message-ID: <CALAqxLX=csTtnqr2Hc9v_R8ex8zPj_P1JvSyjZXUKEqSaF=gPA@mail.gmail.com>
Date:   Wed, 25 Sep 2019 21:06:34 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     Chunfeng Yun <chunfeng.yun@...iatek.com>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Felipe Balbi <balbi@...nel.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Yu Chen <chenyu56@...wei.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Linux USB List <linux-usb@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH 4/5] dt-bindings: usb: dwc3: of-simple: add compatible for HiSi

On Wed, Sep 25, 2019 at 6:34 PM Chunfeng Yun <chunfeng.yun@...iatek.com> wrote:
> On Wed, 2019-09-25 at 23:42 +0000, John Stultz wrote:
> > +++ b/Documentation/devicetree/bindings/usb/hisi,dwc3.txt
> > @@ -0,0 +1,52 @@
> > +HiSi SuperSpeed DWC3 USB SoC controller
> > +
> > +Required properties:
> > +- compatible:                should contain "hisilicon,hi3660-dwc3" for HiSi SoC
> > +- clocks:            A list of phandle + clock-specifier pairs for the
> > +                     clocks listed in clock-names
> > +- clock-names:               Should contain the following:
> > +  "clk_usb3phy_ref"  Phy reference clk
> It's not good idea to apply phy's clock in dwc3's node

Hey! Thanks for taking a look at this!

So first, my apologies, I'm not the driver author and I don't have any
real specs on the hardware other then what's in the source tree I'm
working on.  Not the ideal person to be documenting the binding, but I
realized we still needed some binding documentation (although a few
other dwc-of-simple compat entries are undocumented), so this is my
rough stab at it. :/

Given the name clk_usb3phy_ref I'm assuming its a phy reference clock,
but I honestly don't know if I'm getting that wrong.  It all seems to
be leveraging the fact that the dwc-of-simple driver batch enables and
disables all the clocks w/o really looking at the names.

Do you have a recommendation for what would be best here? I suspect
it's necessary to enable/disable the clk in a similar path(though I'm
unfortunately traveling this week so I can't validate that). Do I try
to move the clk_usb3phy_ref clock enable/disable handling to somewhere
else?

thanks
-john