Re: [PATCH 3/3] memory: renesas-rpc-if: Add support for RZ/T2H SoC

[Geert Uytterhoeven]

Hi Krzysztof,

On Mon, 16 Mar 2026 at 15:21, Krzysztof Kozlowski <krzk@xxxxxxxxxx> wrote:
> On 16/03/2026 15:16, Wolfram Sang wrote:
> >> Add a new compatible string "renesas,r9a09g077-xspi" for RZ/T2H while
> >> reusing the existing xspi_info_r9a09g047 OF data. This allows the driver
> >> to bind correctly on RZ/T2H while the register differences can be handled
> >> in future updates as the affected configuration registers are not currently
> >> accessed by the driver.
> >
> > This sounds fragile to me. Can you add a comment somewhere in the driver
> > or headers so people wanting to use these registers will find out that
> > the SoCs are not compatible anymore?
>
> IMO, this patch is not needed. If you need to handle differences in
> registers, then you add dedicated OF data.
>
> The change here (with the bindings) is actually confusing, because
> effectively it says two contradictory statements:
> 1. Driver patch: devices are different but they are compatible in
> meaning of DT,
> 2. Bindings: devices are not compatible
>
> So you need to decide which above, but not both.
>
> Eventually provide extensive arguments in terms of how DT understands
> compatibility.

I disagree.  Using the same of_data can does not mean the devices are
100% compatible.  It can also mean that the devices are different, but
  a) The differences are not handled yet, because the extra features of
     one variant (or both variants)  are not yet supported by the driver,
  b) The differences are not handled explicitly, but implicitly,
     or elsewhere.
     E.g. the different number of resets is handled implicitly through
     devm_reset_control_array_get_exclusive().

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

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