From mboxrd@z Thu Jan  1 00:00:00 1970
From: Rob Herring <robh+dt@kernel.org>
Subject: Re: [PATCH v2 1/2] spi: dt-bindings: spi-controller: Fix
 #address-cells for slave mode
Date: Wed, 4 Mar 2020 09:12:55 -0600
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Cc: Geert Uytterhoeven <geert+renesas@glider.be>,
        Mark Brown <broonie@kernel.org>,
        Maxime Ripard <mripard@kernel.org>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
        linux-spi <linux-spi@vger.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
        <devicetree@vger.kernel.org>,
        "open list:MEDIA DRIVERS FOR RENESAS - FCP"
        <linux-renesas-soc@vger.kernel.org>
To: Geert Uytterhoeven <geert@linux-m68k.org>
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On Wed, Mar 4, 2020 at 6:50 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> Hi Rob,
>
> On Tue, Mar 3, 2020 at 10:05 PM Rob Herring <robh+dt@kernel.org> wrote:
> > On Tue, Mar 3, 2020 at 3:45 AM Geert Uytterhoeven
> > <geert+renesas@glider.be> 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@renesas.com>
> > > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> > > ---
> > > 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