linux-kernel - Re: [PATCH v3 2/3] dt-bindings: phy: Add constants for lan966x serdes

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Message-ID: <CAL_JsqLemN4jU32-5UvPBGUb7G6jxxKwD5oetJWkoBLANuyTsw@mail.gmail.com>
Date:   Tue, 19 Oct 2021 08:38:49 -0500
From:   Rob Herring <robh@...nel.org>
To:     Horatiu Vultur <horatiu.vultur@...rochip.com>
Cc:     Kishon Vijay Abraham I <kishon@...com>, Vinod <vkoul@...nel.org>,
        Andrew Lunn <andrew@...n.ch>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        linux-phy@...ts.infradead.org, devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/3] dt-bindings: phy: Add constants for lan966x serdes

On Tue, Oct 19, 2021 at 4:11 AM Horatiu Vultur
<horatiu.vultur@...rochip.com> wrote:
>
> The 10/18/2021 14:28, Rob Herring wrote:
> >
> > On Fri, Oct 15, 2021 at 02:39:19PM +0200, Horatiu Vultur wrote:
> > > Lan966x has: 2 integrated PHYs, 3 SerDes and 2 RGMII interfaces. Which
> > > requires to be muxed based on the HW representation.
> > >
> > > So add constants for each interface to be able to distinguish them.
> > >
> > > Signed-off-by: Horatiu Vultur <horatiu.vultur@...rochip.com>
> > > ---
> > >  include/dt-bindings/phy/phy-lan966x-serdes.h | 14 ++++++++++++++
> > >  1 file changed, 14 insertions(+)
> > >  create mode 100644 include/dt-bindings/phy/phy-lan966x-serdes.h
> > >
> > > diff --git a/include/dt-bindings/phy/phy-lan966x-serdes.h b/include/dt-bindings/phy/phy-lan966x-serdes.h
> > > new file mode 100644
> > > index 000000000000..8a05f93ecf41
> > > --- /dev/null
> > > +++ b/include/dt-bindings/phy/phy-lan966x-serdes.h
> > > @@ -0,0 +1,14 @@
> > > +/* SPDX-License-Identifier: (GPL-2.0 OR MIT) */
> > > +
> > > +#ifndef __PHY_LAN966X_SERDES_H__
> > > +#define __PHY_LAN966X_SERDES_H__
> > > +
> > > +#define PHY(x)               (x)
> > > +#define PHY_MAX              PHY(2)
> > > +#define SERDES6G(x)  (PHY_MAX + 1 + (x))
> > > +#define SERDES6G_MAX SERDES6G(3)
> > > +#define RGMII(x)     (SERDES6G_MAX + 1 + (x))
> > > +#define RGMII_MAX    RGMII(2)
> > > +#define SERDES_MAX   (RGMII_MAX + 1)
> >
> > I still don't understand. #phy-cells description says we have:
> >
> > <port idx> <serdes idx>
> >
> > But here it's 3 numbers. How are these defines used to fill in the 2
> > cells?
>
> Actually they are still only a number. Or maybe I am missing something.

So all the defines apply to the 2nd cell? That's what's missing. The
cell description needs to spell all this out. 3 different modes or
whatever. Explain what the h/w is comprised of in the top level
'description'.

>
> Maybe an example will help:
>
> ---
> serdes: serdes@...04010 {
>     compatible = "microchip,lan966x-serdes";
>     reg = <0xe202c000 0x9c>, <0xe2004010 0x4>;
>     #phy-cells = <2>;
> };
>
> &port0 {
>     ...
>     phys = <&serdes 0 SERDES6G(1)>;
>     ...
> };
>
> &port1 {
>     ...
>     phys = <&serdes 1 PHY(0)>;

I think CU was better, just needed some comments. PHY is pretty vague.

>     ...
> }
>
> ...
> ---
>
> Here are some existing examples based on which I have created this patch
> series:
> https://elixir.bootlin.com/linux/v5.15-rc6/source/arch/mips/boot/dts/mscc/ocelot_pcb120.dts#L99

None of which use PHY() or RGMII()...


> https://elixir.bootlin.com/linux/v5.15-rc6/source/arch/mips/boot/dts/mscc/ocelot.dtsi#L274
>
> >
> > Rob
>
> --
> /Horatiu