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From:   Saravana Kannan <saravanak@google.com>
Date:   Mon, 22 Jul 2019 16:40:53 -0700
Message-ID: <CAGETcx9GzQj0ZHNF+uR2cGHUkQ5sOPYEwyXKK1dJ2sJbHVSVyw@mail.gmail.com>
Subject: Re: [PATCH v3 1/6] dt-bindings: opp: Introduce opp-peak-KBps and
 opp-avg-KBps bindings
To:     Rob Herring <robh@kernel.org>
Cc:     Sibi Sankar <sibis@codeaurora.org>,
        Georgi Djakov <georgi.djakov@linaro.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Viresh Kumar <vireshk@kernel.org>, Nishanth Menon <nm@ti.com>,
        Stephen Boyd <sboyd@kernel.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        "Sweeney, Sean" <seansw@qti.qualcomm.com>,
        daidavid1@codeaurora.org, Rajendra Nayak <rnayak@codeaurora.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Evan Green <evgreen@chromium.org>,
        Android Kernel Team <kernel-team@android.com>,
        Linux PM <linux-pm@vger.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>
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On Mon, Jul 22, 2019 at 4:35 PM Rob Herring <robh@kernel.org> wrote:
>
> On Tue, Jul 16, 2019 at 11:58:08AM -0700, Saravana Kannan wrote:
> > On Tue, Jul 16, 2019 at 10:25 AM Sibi Sankar <sibis@codeaurora.org> wrote:
> > >
> > > Hey Saravana,
> > >
> > > https://patchwork.kernel.org/patch/10850815/
> > > There was already a discussion ^^ on how bandwidth bindings were to be
> > > named.
> >
> > Yes, I'm aware of that series. That series is trying to define a BW
> > mapping for an existing frequency OPP table. This patch is NOT about
> > adding a mapping to an existing table. This patch is about adding the
> > notion of BW OPP tables where BW is the "key" instead of "frequency".
> >
> > So let's not mixed up these two series.
>
> Maybe different reasons, but in the end we'd end up with 2 bandwidth
> properties. We need to sort out how they'd overlap/coexist.

Oh, I totally agree! My point is that the other mapping isn't the
right approach because it doesn't handle a whole swath of use cases.
The one I'm proposing can act as a super set of the other (as in, can
handle that use case too).

> The same comment in that series about defining a standard unit suffix
> also applies to this one.

I thought I read that whole series and I don't remember reading about
the unit suffix. But I'll take a closer look. I've chosen to keep the
DT units at least as "high of a resolution" as what the APIs accept
today. The APIs take KB/s. So I make sure DT can capture KB/s
differences. If we all agree that KB/s is "too accurate" then I think
we should change everything to MB/s.

-Saravana