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    Subject[PATCH/RFC v2 1/7] spi: Document DT bindings for SPI controllers in slave mode
    Date
    Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
    ---
    v2:
    - Do not create a child node in SPI slave mode. Instead, add an
    "spi-slave" property, and put the mode properties in the controller
    node.
    ---
    Documentation/devicetree/bindings/spi/spi-bus.txt | 34 ++++++++++++++---------
    1 file changed, 21 insertions(+), 13 deletions(-)

    diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt b/Documentation/devicetree/bindings/spi/spi-bus.txt
    index 17822860cb98c34d..1ae28d7cafb68dc5 100644
    --- a/Documentation/devicetree/bindings/spi/spi-bus.txt
    +++ b/Documentation/devicetree/bindings/spi/spi-bus.txt
    @@ -1,17 +1,23 @@
    SPI (Serial Peripheral Interface) busses

    -SPI busses can be described with a node for the SPI master device
    -and a set of child nodes for each SPI slave on the bus. For this
    -discussion, it is assumed that the system's SPI controller is in
    -SPI master mode. This binding does not describe SPI controllers
    -in slave mode.
    +SPI busses can be described with a node for the SPI controller device
    +and a set of child nodes for each SPI slave on the bus. The system's SPI
    +controller may be described for use in SPI master mode or in SPI slave mode,
    +but not for both at the same time.

    -The SPI master node requires the following properties:
    +The SPI controller node requires the following properties:
    +- compatible - name of SPI bus controller following generic names
    + recommended practice.
    +
    +In master mode, the SPI controller node requires the following additional
    +properties:
    - #address-cells - number of cells required to define a chip select
    address on the SPI bus.
    - #size-cells - should be zero.
    -- compatible - name of SPI bus controller following generic names
    - recommended practice.
    +
    +In slave mode, the SPI controller node requires one additional property:
    +- spi-slave - Empty property.
    +
    No other properties are required in the SPI bus node. It is assumed
    that a driver for an SPI bus device will understand that it is an SPI bus.
    However, the binding does not attempt to define the specific method for
    @@ -21,7 +27,7 @@ assumption that board specific platform code will be used to manage
    chip selects. Individual drivers can define additional properties to
    support describing the chip select layout.

    -Optional properties:
    +Optional properties (master mode only):
    - cs-gpios - gpios chip select.
    - num-cs - total number of chipselects.

    @@ -41,12 +47,14 @@ cs1 : native
    cs2 : &gpio1 1 0
    cs3 : &gpio1 2 0

    -SPI slave nodes must be children of the SPI master node and can
    -contain the following properties.
    -- reg - (required) chip select address of device.
    +In master mode, SPI slave nodes must be children of the SPI controller node.
    +In slave mode, the (single) slave device is represented by the controller node
    +itself. SPI slave nodes can contain the following properties.
    +- reg - (required, master mode only) chip select address of device.
    - compatible - (required) name of SPI device following generic names
    recommended practice.
    -- spi-max-frequency - (required) Maximum SPI clocking speed of device in Hz.
    +- spi-max-frequency - (required, master mode only) Maximum SPI clocking speed
    + of device in Hz.
    - spi-cpol - (optional) Empty property indicating device requires
    inverse clock polarity (CPOL) mode.
    - spi-cpha - (optional) Empty property indicating device requires
    --
    1.9.1
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