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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Mon, 20 May 2019 09:44:48 +0200
Message-ID: <CAMuHMdU5a2qXVG52Creftp4wR_nnwB9xk=jFeiOWUO0vJSyV0w@mail.gmail.com>
Subject: Re: [PATCH v12 3/3] dt-bindings: mfd: Document Renesas R-Car Gen3
 RPC-IF MFD bindings
To:     Mason Yang <masonccyang@mxic.com.tw>
Cc:     Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>,
        Lee Jones <lee.jones@linaro.org>,
        Boris Brezillon <bbrezillon@kernel.org>,
        Mark Brown <broonie@kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Simon Horman <horms@verge.net.au>, juliensu@mxic.com.tw,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
        linux-spi <linux-spi@vger.kernel.org>,
        Marek Vasut <marek.vasut@gmail.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Rob Herring <robh@kernel.org>, zhengxunli@mxic.com.tw,
        Miquel Raynal <miquel.raynal@bootlin.com>
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Hi Mason,

On Mon, May 20, 2019 at 9:24 AM <masonccyang@mxic.com.tw> wrote:
> > >>>   - clocks: should contain 1 entries for the module's clock
> > >>>   - clock-names: should contain "rpc"
> > >>
> > >>    I suspect we'd need the RPC/RPCD2 clocks mentioned as well (not
> sure
> > > yet)...
> > >
> > > Need it ?
> >
> >    You seem to call clk_get_rate() on the module clock, I doubt that's
> > correct topologically...
>
> I think it's correct but just like Geert mentioned that there is no any
> patch
> in drivers/clk/renesas/r8a77995-cpg-mssr.c adding RPC-related clocks.
>
>
> I patched dt-bindings/clock/r8a77995-cpg-mssr.h for some simple testing
>
> -#define R8A77995_CLK_RPC               29
> -#define R8A77995_CLK_RPCD2             30
> +#define R8A77995_CLK_RPC               31
> +#define R8A77995_CLK_RPCD2             32

That change doesn't make sense to me...

> by clk_prepare_enable() & clk_disable_unprepare() with CPG_MOD 917
> on D3 draak board, it is working fine.

... and is not sufficient to allow the above two calls.

Besides, making explicit clk_prepare_enable() calls bypasses Runtime PM
and the automatic disabling of unused clocks, thus hiding bugs related to
Runtime PM.  Which is probably why your driver doesn't work for Sergei...


Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds