Re: [PATCH v2 1/2] spi: dt-bindings: spi-controller: Fix #address-cells for slave mode

[Rob Herring <robh+dt@xxxxxxxxxx>]

On Wed, Mar 4, 2020 at 6:50 AM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
>
> Hi Rob,
>
> On Tue, Mar 3, 2020 at 10:05 PM Rob Herring <robh+dt@xxxxxxxxxx> wrote:
> > On Tue, Mar 3, 2020 at 3:45 AM Geert Uytterhoeven
> > <geert+renesas@xxxxxxxxx> wrote:
> > > Currently, the DT bindings for an SPI controller specify that
> > > "#address-cells" must be fixed to one.  However, that applies to an SPI
> > > controller in master mode only.  When running in SPI slave mode,
> > > "#address-cells" should be zero.
> > >
> > > Fix this making the value of "#address-cells" dependent on the presence
> > > of "spi-slave".
> > >
> > > Fixes: 0a1b929356830257 ("spi: Add YAML schemas for the generic SPI options")
> > > Reported-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
> > > Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> > > ---
> > > v2:
> > >   - Use "enum: [0, 1]" instead of min/max limit,
> > >   - use "- spi-slave" instead of "[ spi-slave ]".
> > >
> > > As of dtc commit 403cc79f06a135ae ("checks: Update SPI bus check for
> > > 'spi-slave'") and Linux commit c2e7075ca8303631 ("scripts/dtc: Update to
> > > upstream version v1.4.7-57-gf267e674d145"), dtc knows about SPI slave.
> > >
> > > However, when using "#address-cells = <0>" with W=1:
> > >
> > >     Warning (avoid_unnecessary_addr_size): /soc/spi@e6e10000: unnecessary #address-cells/#size-cells without "ranges" or child "reg" property
> >
> > What was the point in having #address-cells in the first place for
> > slaves?
>
> I don't know, commit a8830cb19cfea04e ("spi: Document DT bindings for
> SPI controllers in slave mode") doesn't require any #address-cells for
> slave mode.
>
> Perhaps because node_addr_cells() in dtc defaults to 2?
> Or because of_bus_n_addr_cells() walks up the parent chain and thus
> defaults to the first found parent value?
>
> > Seems like we should make it mutually exclusive with 'spi-slave'.
>
> Sounds like a good idea. How to express that in yaml?

oneOf:
  - required:
      - "#address-cells"
  - required:
      - spi-slave

Rob