linux-kernel - Re: [PATCH v12 3/3] dt-bindings: mfd: Document Renesas R-Car Gen3 RPC-IF MFD bindings

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Date:   Tue, 14 May 2019 12:07:54 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Mason Yang <masonccyang@...c.com.tw>
Cc:     Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        Lee Jones <lee.jones@...aro.org>,
        Boris Brezillon <bbrezillon@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Simon Horman <horms@...ge.net.au>, juliensu@...c.com.tw,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        linux-spi <linux-spi@...r.kernel.org>,
        Marek Vasut <marek.vasut@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh@...nel.org>, zhengxunli@...c.com.tw
Subject: Re: [PATCH v12 3/3] dt-bindings: mfd: Document Renesas R-Car Gen3
 RPC-IF MFD bindings

Hi Mason,

On Tue, May 14, 2019 at 11:46 AM <masonccyang@...c.com.tw> wrote:
> > >> There's precedence for such constructs being an MFD: please see
> > >> drivers/mfd/at91-usart.c, which registers a single MFD cell for
> > >           second for the direct mapping read mode and
> > >           third for the write buffer area.
> > >   - reg-names: should contain "regs", "dirmap" and "wbuf"
> > >   - 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 ?
> RPCD2 is derived from RPC and it's value is half of RPC,
> i.e., RPC = 160MHz, RPCD2 = 80 MHz

That hierarchy depends on the actual SoC, right?
AFAIU, both are derived from RPCSRC, and can be controlled individually
on some SoCs.

BTW, I still haven't seen a patch for drivers/clk/renesas/r8a77995-cpg-mssr.c
adding RPC-related clocks, so I have no idea what's the Linux view of the
hierarchy on your system.

Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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