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
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:
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