diff options
Diffstat (limited to 'dts/Bindings/spi/spi-bus.txt')
| -rw-r--r-- | dts/Bindings/spi/spi-bus.txt | 35 |
1 files changed, 18 insertions, 17 deletions
diff --git a/dts/Bindings/spi/spi-bus.txt b/dts/Bindings/spi/spi-bus.txt index 42d595425d..17822860cb 100644 --- a/dts/Bindings/spi/spi-bus.txt +++ b/dts/Bindings/spi/spi-bus.txt @@ -8,11 +8,10 @@ in slave mode. The SPI master node requires the following properties: - #address-cells - number of cells required to define a chip select - address on the SPI bus. + address on the SPI bus. - #size-cells - should be zero. - compatible - name of SPI bus controller following generic names - recommended practice. -- cs-gpios - (optional) gpios chip select. + recommended practice. 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 @@ -22,11 +21,12 @@ 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 property: -- num-cs : total number of chipselects +Optional properties: +- cs-gpios - gpios chip select. +- num-cs - total number of chipselects. -If cs-gpios is used the number of chip select will automatically increased -with max(cs-gpios > hw cs) +If cs-gpios is used the number of chip selects will be increased automatically +with max(cs-gpios > hw cs). So if for example the controller has 2 CS lines, and the cs-gpios property looks like this: @@ -45,29 +45,30 @@ SPI slave nodes must be children of the SPI master node and can contain the following properties. - reg - (required) 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 + recommended practice. +- spi-max-frequency - (required) Maximum SPI clocking speed of device in Hz. - spi-cpol - (optional) Empty property indicating device requires - inverse clock polarity (CPOL) mode + inverse clock polarity (CPOL) mode. - spi-cpha - (optional) Empty property indicating device requires - shifted clock phase (CPHA) mode + shifted clock phase (CPHA) mode. - spi-cs-high - (optional) Empty property indicating device requires - chip select active high + chip select active high. - spi-3wire - (optional) Empty property indicating device requires - 3-wire mode. + 3-wire mode. - spi-lsb-first - (optional) Empty property indicating device requires LSB first mode. -- spi-tx-bus-width - (optional) The bus width(number of data wires) that +- spi-tx-bus-width - (optional) The bus width (number of data wires) that is used for MOSI. Defaults to 1 if not present. -- spi-rx-bus-width - (optional) The bus width(number of data wires) that +- spi-rx-bus-width - (optional) The bus width (number of data wires) that is used for MISO. Defaults to 1 if not present. - spi-rx-delay-us - (optional) Microsecond delay after a read transfer. - spi-tx-delay-us - (optional) Microsecond delay after a write transfer. Some SPI controllers and devices support Dual and Quad SPI transfer mode. -It allows data in the SPI system to be transferred in 2 wires(DUAL) or 4 wires(QUAD). +It allows data in the SPI system to be transferred using 2 wires (DUAL) or 4 +wires (QUAD). Now the value that spi-tx-bus-width and spi-rx-bus-width can receive is -only 1(SINGLE), 2(DUAL) and 4(QUAD). +only 1 (SINGLE), 2 (DUAL) and 4 (QUAD). Dual/Quad mode is not allowed when 3-wire mode is used. If a gpio chipselect is used for the SPI slave the gpio number will be passed |