diff mbox series

[v2,1/2] dt-bindings: spi: Document binding for generic SPI multiplexer

Message ID 20200123012317.14808-2-chris.packham@alliedtelesis.co.nz (mailing list archive)
State Superseded
Headers show
Series SPI bus multiplexing | expand

Commit Message

Chris Packham Jan. 23, 2020, 1:23 a.m. UTC 
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

 .../devicetree/bindings/spi/spi-mux.yaml      | 84 +++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/spi/spi-mux.yaml

Comments

Rob Herring Jan. 23, 2020, 1:51 p.m. UTC | #1 
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?

>
>  .../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
>
Chris Packham Jan. 26, 2020, 8:23 p.m. UTC | #2 
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
> >
Rob Herring Jan. 27, 2020, 1:56 p.m. UTC | #3 
On Sun, Jan 26, 2020 at 2:24 PM Chris Packham
<Chris.Packham@alliedtelesis.co.nz> wrote:
>
> 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

Note that you need to run this also without DT_SCHEMA_FILES set so the
example is checked against all schema. With that, the 'spi' node is
going to need #address-cells and #size-cells.

>
> 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?

We should probably relax dtc, but for now I'd just use 'spi'.

Rob
diff mbox series

Patch

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>
+
+         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>;
+         };
+       };
+     };