linux-kernel - Re: [PATCH v4 6/9] usb: dwc3: Rework resets initialization to be more flexible

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Date:   Tue, 29 Oct 2019 11:05:59 -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 6/9] usb: dwc3: Rework resets initialization to be more flexible

On Tue, Oct 29, 2019 at 2:17 AM Felipe Balbi <balbi@...nel.org> wrote:
> John Stultz <john.stultz@...aro.org> writes:
> > The dwc3 core binding specifies one reset.
> >
> > However some variants of the hardware my not have more.
>                                         ^^
>                                         may
>
> According to synopsys databook, there's a single *input* reset signal on
> this IP. What is this extra reset you have?
>
> Is this, perhaps, specific to your glue layer around the synopsys ip?

Likely (again, I unfortunately don't have a ton of detail on the hardware).

> Should, perhaps, your extra reset be managed by the glue layer?

So yes the dwc3-of-simple does much of this already (it handles
multiple resets, and variable clocks), but unfortunately we seem to
need new bindings for each device added?  I think the suggestion from
Rob was due to the sprawl of bindings for the glue code, and the extra
complexity of the parent node.  So I believe Rob just thought it made
sense to collapse this down into the core?

I'm not really passionate about either approach, and am happy to
rework (as long as there is eventual progress :).
Just let me know what you'd prefer.

thanks
-john