Re: [PATCH v5 7/7] dts: ti: k3-am625-beagleplay: Add mikroBUS

[Geert Uytterhoeven <geert@linux-m68k.org>]

On Fri, Jul 5, 2024 at 10:01 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> On Thu, 27 Jun 2024, Michael Walle wrote:
> > On Thu Jun 27, 2024 at 7:07 PM CEST, Andrew Davis wrote:
> >>> +   mikrobus_boards {
> >>> +           thermo_click: thermo-click {
> >>> +                   compatible = "maxim,max31855k", "mikrobus-spi";
> >>
> >> I might be missing something, but your solution cannot possibly be
> >> to list every click board that could be connected (all 1500+ of them)
> >> to every mikroBUS connector on every device's DT file..
> >>
> >> Each click board should have a single DTSO overlay file to describe the
> >> click board, one per click board total. And then that overlay should
> >> apply cleanly to any device that has a mikroBUS interface.
> >>
> >> Which means you have not completely solved the fundamental problem of
> >> abstracting the mikroBUS connector in DT. Each of these click device child
> >> nodes has to be under the parent connector node. Which means a phandle
> >> to the parent node, which is not generically named. For instance
> >> if my board has 2 connectors, I would have mikrobus0 and mikrobus1,
> >> the click board's overlay would look like this:
> >>
> >> /dts-v1/;
> >> /plugin/;
> >>
> >> &mikrobus0 {
>
> Let's use just "&mikrobus" instead...
>
> >>      status = "okay";
> >>
> >>      mikrobus_board {
> >>              thermo-click {
> >>                      compatible = "maxim,max31855k", "mikrobus-spi";

Max31855k is an SPI device, so its device node should be under an "spi"
subnode (with proper #{address,size}-cells) of the mikrobus connector,
and use a suitable unit-address and "reg" property, pointing to the
right SPI chip select.

> >>                      spi-max-frequency = <1000000>;

This belongs to the "spi" subnode, not the Max31855k device node.

> >>                      pinctrl-apply = "spi_default";

This belongs to the mikrobus connector node.

> >>              };
> >>      };
> >> };

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