linux-kernel - Re: [PATCH 04/18] arm64: dts: renesas: beacon kit: Fix Audio Clock sources

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Date:   Fri, 18 Dec 2020 14:05:00 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Adam Ford <aford173@...il.com>
Cc:     Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Adam Ford-BE <aford@...conembedded.com>,
        Magnus Damm <magnus.damm@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 04/18] arm64: dts: renesas: beacon kit: Fix Audio Clock sources

Hi Adam,

On Thu, Dec 17, 2020 at 1:01 PM Adam Ford <aford173@...il.com> wrote:
> On Thu, Dec 17, 2020 at 4:54 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > On Sun, Dec 13, 2020 at 7:38 PM Adam Ford <aford173@...il.com> wrote:
> > > The SoC was expecting two clock sources with different frequencies.
> > > One to support 44.1KHz and one to support 48KHz.  With the newly added
> > > ability to configure the programmably clock, configure both clocks.
> > >
> > > Beacause the SoC is expecting a fixed clock/oscillator, it doesn't
> > > attempt to get and enable the clock for audio_clk_a. The choice to
> > > use a fixed-factor-clock was due to the fact that it will automatically
> > > enable the programmable clock frequency without change any code.
> > >
> > > Signed-off-by: Adam Ford <aford173@...il.com>
> >
> > Thanks for your patch!
> >
> > > --- a/arch/arm64/boot/dts/renesas/beacon-renesom-baseboard.dtsi
> > > +++ b/arch/arm64/boot/dts/renesas/beacon-renesom-baseboard.dtsi
> > > @@ -250,9 +250,12 @@ ss_ep: endpoint {
> > >  };
> > >
> > >  &audio_clk_a {
> > > -       clock-frequency = <24576000>;
> > > -       assigned-clocks = <&versaclock6_bb 4>;
> > > -       assigned-clock-rates = <24576000>;
> > > +       /delete-property/ clock-frequency;
> > > +       #clock-cells = <0>;
> > > +       compatible = "fixed-factor-clock";
> > > +       clock-mult = <1>;
> > > +       clock-div = <1>;
> > > +       clocks = <&versaclock6_bb 4>;
> > >  };
> >
> > Shouldn't you override the clocks property in the rcar_sound node
> > instead, like is done in several other board DTS files (with cs2000)?
> >
>
> I guess there are multiple ways to do this.  Because the rcar_sound
> was already expecting a reference to audio_clk_a, it seemed less
> intrusive this way. The way I proposed, we can use the default
> rcar_sound clocking and just change the audio_clk node to enable the
> versaclock output.  The versaclock is driving the audio_clk_a
> reference clock, so it seemed appropriate to put it there.
>
> If you want me to change, I will.

Taking a fresh look at this, I start to like it.
What do other people think?

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