linux-kernel - Re: [PATCH v7 07/13] dt-bindings: memory-controllers: add Exynos5422 DMC device description

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Message-ID: <CAL_JsqJSbi5jNZSRhiE-h74DdbsgM7O+tqP9HOf037pyN7TbFA@mail.gmail.com>
Date:   Wed, 8 May 2019 15:35:15 -0500
From:   Rob Herring <robh@...nel.org>
To:     Lukasz Luba <l.luba@...tner.samsung.com>
Cc:     Krzysztof Kozlowski <krzk@...nel.org>, devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "open list:THERMAL" <linux-pm@...r.kernel.org>,
        "linux-samsung-soc@...r.kernel.org" 
        <linux-samsung-soc@...r.kernel.org>,
        Bartłomiej Żołnierkiewicz 
        <b.zolnierkie@...sung.com>, Kukjin Kim <kgene@...nel.org>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kees Cook <keescook@...omium.org>,
        Tony Lindgren <tony@...mide.com>,
        Joerg Roedel <jroedel@...e.de>,
        Thierry Reding <treding@...dia.com>,
        Dmitry Osipenko <digetx@...il.com>, willy.mh.wolff.ml@...il.com
Subject: Re: [PATCH v7 07/13] dt-bindings: memory-controllers: add Exynos5422
 DMC device description

On Wed, May 8, 2019 at 4:45 AM Lukasz Luba <l.luba@...tner.samsung.com> wrote:
>
>
> On 5/8/19 9:19 AM, Krzysztof Kozlowski wrote:
> > On Tue, 7 May 2019 at 19:04, Rob Herring <robh@...nel.org> wrote:
> >>> +- devfreq-events : phandles of the PPMU events used by the controller.
> >>> +- samsung,syscon-chipid : phandle of the ChipID used by the controller.
> >>> +- samsung,syscon-clk : phandle of the clock register set used by the controller.
> >>
> >> Looks like a hack. Can't you get this from the clocks property? What is
> >> this for?
> >
> > Hi Rob,
> >
> > Lukasz uses these two syscon regmaps to read certain registers. For
> > chipid he reads it to check the size of attached memory (only 2 GB
> > version is supported). This indeed looks like a hack. However the
> > second regmap (clk) is needed to get the timing data from registers
> > from DMC clock driver address space. These are registers with memory
> > timing so their data is not exposed anyway in common clk framework.

Okay, please just explain what your accessing. Consider adding the
offset as a cell in case stuff moves around on another chip.

> >
> > Best regards,
> > Krzysztof
>
> Thank you Krzysztof for a fast response. I have also responded to Rob.
> I wouldn't call accessing chipid registers as a hack, though. The DMC
> registers do not contain information about the memory chip since it is
> in phase of production the board not the chip. Thus, chipid regs (which
> loads from e-fuses) are best place to put information about memory
> type/size.

For efuses, we have a binding (nvmem). Maybe you should use it.

Rob