linux-kernel - Re: [PATCH v4 2/6] dt: bindings: add mt7621-clk device tree binding documentation

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Message-ID: <CAMhs-H9SiZ90NYCGL+3ad9UR7CDUiA1gb99ZcfHp10=SZtVPpg@mail.gmail.com>
Date:   Thu, 17 Dec 2020 11:38:37 +0100
From:   Sergio Paracuellos <sergio.paracuellos@...il.com>
To:     Stephen Boyd <sboyd@...nel.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        John Crispin <john@...ozen.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Greg KH <gregkh@...uxfoundation.org>,
        Chuanhong Guo <gch981213@...il.com>,
        Weijie Gao <hackpascal@...il.com>,
        COMMON CLK FRAMEWORK <linux-clk@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "open list:MIPS <linux-mips@...r.kernel.org>, open list:STAGING
        SUBSYSTEM <devel@...verdev.osuosl.org>, NeilBrown <neil@...wn.name>,
        open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH v4 2/6] dt: bindings: add mt7621-clk device tree binding documentation

On Thu, Dec 17, 2020 at 11:32 AM Stephen Boyd <sboyd@...nel.org> wrote:
>
> Quoting Sergio Paracuellos (2020-12-17 02:14:10)
> > On Thu, Dec 17, 2020 at 11:07 AM Stephen Boyd <sboyd@...nel.org> wrote:
> > >
> > > Quoting Sergio Paracuellos (2020-12-17 02:01:39)
> > > >
> > > > On Thu, Dec 17, 2020 at 9:58 AM Stephen Boyd <sboyd@...nel.org> wrote:
> > > > >
> > > > > Quoting Sergio Paracuellos (2020-11-22 01:55:52)
> > > > >
> > > > > > diff --git a/Documentation/devicetree/bindings/clock/mediatek,mt7621-clk.yaml b/Documentation/devicetree/bindings/clock/mediatek,mt7621-clk.yaml
> > > > > > new file mode 100644
> > > > > > index 000000000000..6aca4c1a4a46
> > > > > > --- /dev/null
> > > > > > +++ b/Documentation/devicetree/bindings/clock/mediatek,mt7621-clk.yaml
> > > > >
> > > > > > +      compatible = "mediatek,mt7621-sysc", "syscon";
> > > > > > +      reg = <0x0 0x100>;
> > > > > > +
> > > > > > +      pll {
> > > > >
> > > > > clock-controller? Why can't the parent device be the clk provider and
> > > > > have #clock-cells?
> > > > >
> > > >
> > > > I don't get your point, sorry. Can you please explain this a bit more
> > > > or point to me to an example to understand the real meaning of this?
> > >
> > > It looks like this is a made up child node of syscon so that a driver
> > > can probe in the kernel. It would be more DT friendly to create a
> > > platform device from the parent node's driver, or just register the clks
> > > with the framework directly in that driver.
> >
> > We cannot create a platform device because we need clocks available in
> > 'plat_time_init' before setting up the timer for the GIC.
> > The only way I see to avoid this syscon and having this as a child
> > node is to use architecture operations in
> > 'arch/mips/include/asm/mach-ralink/ralink_regs.h'
> > instead of getting a phandle using the regmap is being currently used...
>
> Can that be done with
>
> CLK_OF_DECLARE_DRIVER("mediatek,mt7621-sysc", my_timer_clk_init)
>
> ? Is the syscon used anywhere besides by the clk driver?

Yes, for example all the gates use them to access SYSC_REG_CLKCFG1 in
all of their 'mt7621_gate_ops' and also in all 'recalc_rate' functions
where SYSC_REG_SYSTEM_CONFIG0, is readed.