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of-bindings: Add binding documentation for SPI busses and devices 

Add documentation about how to describe SPI busses in the device tree.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Segher Boessenkool <segher@kernel.crashing.org>
hifive-unleashed-5.1
Grant Likely 2008-07-11 16:17:57 -06:00
parent a19dd1bd7d
commit 79c28acb2b
1 changed files with 57 additions and 0 deletions
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57
Documentation/powerpc/booting-without-of.txt
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@ -59,6 +59,7 @@ Table of Contents
p) Freescale Synchronous Serial Interface
q) USB EHCI controllers
r) MDIO on GPIOs
s) SPI busses
VII - Marvell Discovery mv64[345]6x System Controller chips
1) The /system-controller node
@ -1881,6 +1882,62 @@ platforms are moved over to use the flattened-device-tree model.
&qe_pio_c 6>;
};
s) 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.
The SPI master node requires the following 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.
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
assigning chip select numbers. Since SPI chip select configuration is
flexible and non-standardized, it is left out of this binding with the
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.
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
- spi-cpol - (optional) Empty property indicating device requires
inverse clock polarity (CPOL) mode
- spi-cpha - (optional) Empty property indicating device requires
shifted clock phase (CPHA) mode
SPI example for an MPC5200 SPI bus:
spi@f00 {
#address-cells = <1>;
#size-cells = <0>;
compatible = "fsl,mpc5200b-spi","fsl,mpc5200-spi";
reg = <0xf00 0x20>;
interrupts = <2 13 0 2 14 0>;
interrupt-parent = <&mpc5200_pic>;
ethernet-switch@0 {
compatible = "micrel,ks8995m";
spi-max-frequency = <1000000>;
reg = <0>;
};
codec@1 {
compatible = "ti,tlv320aic26";
spi-max-frequency = <100000>;
reg = <1>;
};
};
VII - Marvell Discovery mv64[345]6x System Controller chips
===========================================================