Re: [PATCH net-next v5 11/13] ARM: dts: r9a06g032: describe GMAC2

Geert Uytterhoeven
2022-05-20T08:26:21Z

Hi Clément,

On Fri, May 20, 2022 at 10:14 AM Clément Léger
<clement.leger@bootlin.com> wrote:
> Le Fri, 20 May 2022 09:18:58 +0200,
> Geert Uytterhoeven <geert@linux-m68k.org> a écrit :
> > On Thu, May 19, 2022 at 5:32 PM Clément Léger <clement.leger@bootlin.com> wrote:
> > > RZ/N1 SoC includes two MAC named GMACx that are compatible with the
> > > "snps,dwmac" driver. GMAC1 is connected directly to the MII converter
> > > port 1. GMAC2 however can be used as the MAC for the switch CPU
> > > management port or can be muxed to be connected directly to the MII
> > > converter port 2. This commit add description for the GMAC2 which will
> > > be used by the switch description.
> > >
> > > Signed-off-by: Clément Léger <clement.leger@bootlin.com>

> > > --- a/arch/arm/boot/dts/r9a06g032.dtsi
> > > +++ b/arch/arm/boot/dts/r9a06g032.dtsi
> > > @@ -200,6 +200,23 @@ nand_controller: nand-controller@40102000 {
> > > status = "disabled";
> > > };
> > >
> > > + gmac2: ethernet@44002000 {
> > > + compatible = "snps,dwmac";
> >
> > Does this need an SoC-specific compatible value?
>
> Indeed, it might be useful to introduce a specific SoC compatible since
> in a near future, there might be some specific support for that gmac.
> Here is an overview of the gmac connection on the SoC:
>
> ┌─────────┐ ┌──────────┐
> │ │ │ │
> │ GMAC2 │ │ GMAC1 │
> │ │ │ │
> └───┬─────┘ └─────┬────┘
> │ │
> │ │
> │ │
> ┌────▼──────┐ │
> │ │ │
> ┌────────────────────────────┤ SWITCH │ │
> │ │ │ │
> │ ┌─────────────────┴─┬────┬────┘ │
> │ │ ┌──────┘ │ │
> │ │ │ │ │
> ┌────▼──────────▼────────────▼───────────▼─────────────▼────┐
> │ MII Converter │
> │ │
> │ │
> │ port 1 port 2 port 3 port 4 port 5 │
> └───────────────────────────────────────────────────────────┘
>
> As you can see, the GMAC1 is directly connected to MIIC converter and
> thus will need a "pcs-handle" property to point on the MII converter
> port whereas the GMAC2 is directly connected to the switch in GMII.
>
> Is "renesas,r9a06g032-gmac2", "renesas,rzn1-switch-gmac2" looks ok for
> you for this one ?

Why "switch" in the family-specific value, but not in the SoC-specific
value?

Are GMAC1 and GMAC2 really different, or are they identical, and is
the only difference in the wiring, which can be detected at run-time
using this "pcs-handle" property? If they're identical, they should
use the same compatible value.

Thanks!

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