Re: [PATCH net-next v11 1/7] dt-bindings: phy: document the serdes PHY on sa8255p

Hi Bartosz,

On Mon, 29 Jun 2026 at 18:54, Bartosz Golaszewski <[email protected]> wrote:
> On Mon, Jun 29, 2026 at 4:58 PM Geert Uytterhoeven <[email protected]> wrote:
> > On Mon, 29 Jun 2026 at 16:07, Bartosz Golaszewski <[email protected]> wrote:
> > > On Mon, 29 Jun 2026 15:51:31 +0200, Geert Uytterhoeven
> > > <[email protected]> said:
> > > > On Mon, 29 Jun 2026 at 13:29, Bartosz Golaszewski
> > > > <[email protected]> wrote:
> > > >> Describe the SGMII/SerDes PHY present on the Qualcomm sa8255p platforms.
> > > >> This is essentially the same hardware as sa8775p rev3 but the PHY is
> > > >> managed by firmware over SCMI.
> > > >
> > > > So why can't it be reuse the DT bindings, and be compatible with
> > > > qcom,sa8775p-dwmac-sgmii-phy?
> > > >
> > > >> Signed-off-by: Bartosz Golaszewski <[email protected]>
> > > >
> > > >> --- /dev/null
> > > >> +++ b/Documentation/devicetree/bindings/phy/qcom,sa8255p-dwmac-sgmii-phy.yaml
> > > >
> > > >> +  power-domains:
> > > >> +    maxItems: 1
> > > >> +
> > > >> +  power-domain-names:
> > > >> +    items:
> > > >> +      - const: serdes
> > > >
> > > >> +examples:
> > > >> +  - |
> > > >> +    phy@8901000 {
> > > >> +        compatible = "qcom,sa8255p-dwmac-sgmii-phy";
> > > >> +        reg = <0x08901000 0xe10>;
> > > >> +        #phy-cells = <0>;
> > > >> +        power-domains = <&scmi7_dvfs 0>;
> > > >> +        power-domain-names = "serdes";
> > > >
> > > > Ah, this uses power-domains, while the existing bindings for
> > > > qcom,sa8775p-dwmac-sgmii-phy use a clock.
> > > > I guess the clock is the correct hardware description?
> > > >
> > > > Adding to my list of examples for backing a hardware-to-SCMI remapping
> > > > driver...
> > > >
> > >
> > > Russell King asked me to put the PHY logic for SCMI pm domains into the PHY
> > > driver instead of the MAC driver where it was previously. Instead of cramming
> > > both HLOS and firmware handling into the same driver, I figured it makes more
> > > sense to have a dedicated, cleaner driver as the two share very little code (if
> > > any).
> >
> > I think you are mixing up DT bindings and driver implementation?
>
> Ah indeed, but the bindings don't share a lot of content either.

That's the (maintenance) problem: it is essentially the same hardware,
but the DT bindings (and driver) are different. Does this scale?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]

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

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