Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx> --- Documentation/devicetree/bindings/spi/spi-bus.txt | 31 ++++++++++++++--------- 1 file changed, 19 insertions(+), 12 deletions(-) diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt b/Documentation/devicetree/bindings/spi/spi-bus.txt index 17822860cb98c34d..bcd024e0bb9e0009 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 node, the SPI controller node requires the presence of a child node +named "slave", further following the practices for SPI slave nodes below. + 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 +47,13 @@ cs1 : native cs2 : &gpio1 1 0 cs3 : &gpio1 2 0 -SPI slave nodes must be children of the SPI master node and can +SPI slave nodes must be children of the SPI controller node and can contain the following properties. -- reg - (required) chip select address of device. +- 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
