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SubjectRe: [PATCH v2 1/2] dt-bindings: spi: Document binding for generic SPI multiplexer
Date
On Thu, 2020-01-23 at 07:51 -0600, Rob Herring wrote:
> On Wed, Jan 22, 2020 at 7:24 PM Chris Packham
> <chris.packham@alliedtelesis.co.nz> wrote:
> >
> > Add binding documentation for the spi-mux driver. This allows a generic
> > multiplexer to be used to provide access to multiple SPI devices.
> >
> > Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
> > ---
> >
> > Notes:
> > Changes in v2:
> > - update license
> > - make dt_binding_check clean
>
> Sure about that?
>

I was when I wrote that, but now I think I need to consult my spell
book.

It appears the incantation I should be using is

make ARCH=arm defconfig
make ARCH=arm dt_binding_check \
DT_SCHEMA_FILES=Documentation/devicetree/bindings/spi/spi-mux.yaml

I can see the simple failures (not sure how I missed them). But one
that remains is:

Warning (spi_bus_bridge): /example-0/spi/spi-mux@0: node name for SPI
buses should be 'spi'

I could fix that by having

spi {
spi@0 {
compatible = "spi-mux";
};
};

Is that what we want? Or should I be adding awareness of spi-muxes to
dtc?

> >
> > .../devicetree/bindings/spi/spi-mux.yaml | 84 +++++++++++++++++++
> > 1 file changed, 84 insertions(+)
> > create mode 100644 Documentation/devicetree/bindings/spi/spi-mux.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/spi/spi-mux.yaml b/Documentation/devicetree/bindings/spi/spi-mux.yaml
> > new file mode 100644
> > index 000000000000..4bdb31e2257e
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/spi/spi-mux.yaml
> > @@ -0,0 +1,84 @@
> > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/spi/spi-mux.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Generic SPI Multiplexer
> > +
> > +description: |
> > + This binding describes a SPI bus multiplexer to route the SPI chip select
> > + signals. This can be used when you need more devices than the SPI controller
> > + has chip selects available. An example setup is shown in ASCII art; the actual
> > + setting of the multiplexer to a channel needs to be done by a specific SPI mux
> > + driver.
> > +
> > + MOSI /--------------------------------+--------+--------+--------\
> > + MISO |/------------------------------+|-------+|-------+|-------\|
> > + SCL ||/----------------------------+||------+||------+||------\||
> > + ||| ||| ||| ||| |||
> > + +------------+ ||| ||| ||| |||
> > + | SoC ||| | +-+++-+ +-+++-+ +-+++-+ +-+++-+
> > + | ||| | | dev | | dev | | dev | | dev |
> > + | +--+++-+ | CS-X +------+\ +--+--+ +--+--+ +--+--+ +--+--+
> > + | | SPI +-|-------+ Mux |\\ CS-0 | | | |
> > + | +------+ | +--+---+\\\-------/ CS-1 | | |
> > + | | | \\\----------------/ CS-2 | |
> > + | +------+ | | \\-------------------------/ CS-3 |
> > + | | ? +-|----------/ \----------------------------------/
> > + | +------+ |
> > + +------------+
> > +
> > +allOf:
> > + - $ref: "/schemas/spi/spi-controller.yaml#"
> > +
> > +maintainers:
> > + - Chris Packham <chris.packham@alliedtelesis.co.nz>
> > +
> > +properties:
> > + compatible:
> > + const: spi-mux
> > +
> > + mux-controls:
> > + maxItems: 1
> > +
> > +required:
> > + - compatible
> > + - reg
> > + - spi-max-frequency
> > + - mux-controls
> > +
> > +examples:
> > + - |
> > + mux: mux-controller {
> > + compatible = "gpio-mux";
> > + #mux-control-cells = <0>;
> > +
> > + mux-gpios = <&gpio0 3 GPIO_ACTIVE_HIGH>;
> > + };
> > +
> > + spi {
> > + spi-mux@0 {
> > + compatible = "spi-mux";
> > + #address-cells = <1>;
> > + #size-cells = <0>;
> > + reg = <0>;
> > + spi-max-frequency = <100000000>;
> > +
> > + mux-controls = <&mux>
> Missing semicolon.
>
> > +
> > + spi-flash@0 {
> > + compatible = "jedec,spi-nor";
> > + #address-cells = <1>;
> > + #size-cells = <1>;
> > + reg = <0>;
> > + spi-max-frequency = <40000000>;
> > + };
> > +
> > + spi-device@1 {
> > + compatible = "lineartechnology,ltc2488";
> > + reg = <1>;
> > + spi-max-frequency = <10000000>;
> > + };
> > + };
> > + };
> > --
> > 2.25.0
> >
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