This is a revisit of two earlier efforts to add more complex mutliplexing to
SPI busses.
https://patchwork.kernel.org/patch/2706151/
https://patchwork.kernel.org/patch/10897255/
This version makes use of the general purpose mux controller which simplifies
things greatly.
One outstanding problem is the need for the spi-max-frequency on the mux
device. This is not used for anything and is just needed to satisfy the spi
driver infrastructure which expects all spi devices to have this property.
Chris Packham (2):
dt-bindings: spi: Document binding for generic SPI multiplexer
spi: Add generic SPI multiplexer
.../devicetree/bindings/spi/spi-mux.yaml | 89 +++++++++
drivers/spi/Kconfig | 12 ++
drivers/spi/Makefile | 1 +
drivers/spi/spi-mux.c | 189 ++++++++++++++++++
4 files changed, 291 insertions(+)
create mode 100644 Documentation/devicetree/bindings/spi/spi-mux.yaml
create mode 100644 drivers/spi/spi-mux.c
--
2.25.0
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 <[email protected]>
---
Notes:
Changes in v3:
- make dt_binding_check clean (properly this time)
Changes in v2:
- update license
- make dt_binding_check clean
.../devicetree/bindings/spi/spi-mux.yaml | 89 +++++++++++++++++++
1 file changed, 89 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..0ae692dc28b5
--- /dev/null
+++ b/Documentation/devicetree/bindings/spi/spi-mux.yaml
@@ -0,0 +1,89 @@
+# 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 <[email protected]>
+
+properties:
+ compatible:
+ const: spi-mux
+
+ mux-controls:
+ maxItems: 1
+
+required:
+ - compatible
+ - reg
+ - spi-max-frequency
+ - mux-controls
+
+examples:
+ - |
+ #include <dt-bindings/gpio/gpio.h>
+ mux: mux-controller {
+ compatible = "gpio-mux";
+ #mux-control-cells = <0>;
+
+ mux-gpios = <&gpio0 3 GPIO_ACTIVE_HIGH>;
+ };
+
+ spi {
+ #address-cells = <1>;
+ #size-cells = <0>;
+ spi@0 {
+ compatible = "spi-mux";
+ reg = <0>;
+ #address-cells = <1>;
+ #size-cells = <0>;
+ spi-max-frequency = <100000000>;
+
+ mux-controls = <&mux>;
+
+ spi-flash@0 {
+ compatible = "jedec,spi-nor";
+ reg = <0>;
+ #address-cells = <1>;
+ #size-cells = <0>;
+ spi-max-frequency = <40000000>;
+ };
+
+ spi-device@1 {
+ compatible = "lineartechnology,ltc2488";
+ reg = <1>;
+ #address-cells = <1>;
+ #size-cells = <0>;
+ spi-max-frequency = <10000000>;
+ };
+ };
+ };
--
2.25.0
On Thu, Jan 30, 2020 at 8:34 PM Chris Packham
<[email protected]> 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 <[email protected]>
> ---
>
> Notes:
> Changes in v3:
> - make dt_binding_check clean (properly this time)
>
> Changes in v2:
> - update license
> - make dt_binding_check clean
>
> .../devicetree/bindings/spi/spi-mux.yaml | 89 +++++++++++++++++++
> 1 file changed, 89 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/spi/spi-mux.yaml
Reviewed-by: Rob Herring <[email protected]>