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Message-Id: <20190412050213.17698-2-chris.packham@alliedtelesis.co.nz> Date: Fri, 12 Apr 2019 17:02:11 +1200 From: Chris Packham <chris.packham@...iedtelesis.co.nz> To: broonie@...nel.org, robh+dt@...nel.org, mark.rutland@....com Cc: Hamish Martin <hamish.martin@...iedtelesis.co.nz>, linux-spi@...r.kernel.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, Chris Packham <chris.packham@...iedtelesis.co.nz> Subject: [PATCH 1/3] dt-bindings: spi: Add spi-mux-gpio Add binding documentation for spi-mux-gpio which is a slightly more complicated hardware implementation of using gpios to steer SPI chip selects. Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz> --- .../devicetree/bindings/spi/spi-mux-gpio.txt | 45 +++++++++++++++++++ 1 file changed, 45 insertions(+) create mode 100644 Documentation/devicetree/bindings/spi/spi-mux-gpio.txt diff --git a/Documentation/devicetree/bindings/spi/spi-mux-gpio.txt b/Documentation/devicetree/bindings/spi/spi-mux-gpio.txt new file mode 100644 index 000000000000..a32f25321d37 --- /dev/null +++ b/Documentation/devicetree/bindings/spi/spi-mux-gpio.txt @@ -0,0 +1,45 @@ +SPI bus gpio multiplexer + +The SPI bus gpio multiplexer can be used to implement more complicated access +logic than can be supported with the cs-gpios property of a SPI bus. + +In the example below we have a SoC with a single SPI CS that is gated by the +state of a gpio to select the desired SPI device. + + +----------+ CS +-----+ CS0 +----+ + | |--------| |------| | + | | | \ / | +----+ + | SoC | | + | + | | GPIO | / \ | CS1 +----+ + | |--------| |------| | + +----------+ +-----+ +----+ + +Required properties: +- compatible - must be "spi-mux-gpio" +- gpios - gpios used to implement the multiplexing logic +- spi-parent-bus - parent spi bus to use + +Optional properties: +- spi-parent-cs - chip select on parent bus to use. Defaults to 0 if not + specified. + +Example for a multiplexer with a single gpio: + + spi-mux { + compatible = "spi-mux-gpio"; + #address-cells = <1>; + #size-cells = <0>; + gpios = <&gpio0 1 0>; + spi-parent-bus = <&spi0>; + spi-parent-cs = <0>; + + spi-dev@0 { + compatible = "..."; + reg = <0>; + } + + spi-dev@1 { + compatible = "..."; + reg = <1>; + } + }; -- 2.21.0
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