| Kumar Gala | b053dc5 | 2009-06-19 08:31:05 -0500 | [diff] [blame] | 1 | SPI (Serial Peripheral Interface) busses |
| 2 | |
| 3 | SPI busses can be described with a node for the SPI master device |
| 4 | and a set of child nodes for each SPI slave on the bus. For this |
| 5 | discussion, it is assumed that the system's SPI controller is in |
| 6 | SPI master mode. This binding does not describe SPI controllers |
| 7 | in slave mode. |
| 8 | |
| 9 | The SPI master node requires the following properties: |
| 10 | - #address-cells - number of cells required to define a chip select |
| 11 | address on the SPI bus. |
| 12 | - #size-cells - should be zero. |
| 13 | - compatible - name of SPI bus controller following generic names |
| 14 | recommended practice. |
| 15 | No other properties are required in the SPI bus node. It is assumed |
| 16 | that a driver for an SPI bus device will understand that it is an SPI bus. |
| 17 | However, the binding does not attempt to define the specific method for |
| 18 | assigning chip select numbers. Since SPI chip select configuration is |
| 19 | flexible and non-standardized, it is left out of this binding with the |
| 20 | assumption that board specific platform code will be used to manage |
| 21 | chip selects. Individual drivers can define additional properties to |
| 22 | support describing the chip select layout. |
| 23 | |
| 24 | SPI slave nodes must be children of the SPI master node and can |
| 25 | contain the following properties. |
| 26 | - reg - (required) chip select address of device. |
| 27 | - compatible - (required) name of SPI device following generic names |
| 28 | recommended practice |
| 29 | - spi-max-frequency - (required) Maximum SPI clocking speed of device in Hz |
| 30 | - spi-cpol - (optional) Empty property indicating device requires |
| 31 | inverse clock polarity (CPOL) mode |
| 32 | - spi-cpha - (optional) Empty property indicating device requires |
| 33 | shifted clock phase (CPHA) mode |
| 34 | - spi-cs-high - (optional) Empty property indicating device requires |
| 35 | chip select active high |
| 36 | |
| 37 | SPI example for an MPC5200 SPI bus: |
| 38 | spi@f00 { |
| 39 | #address-cells = <1>; |
| 40 | #size-cells = <0>; |
| 41 | compatible = "fsl,mpc5200b-spi","fsl,mpc5200-spi"; |
| 42 | reg = <0xf00 0x20>; |
| 43 | interrupts = <2 13 0 2 14 0>; |
| 44 | interrupt-parent = <&mpc5200_pic>; |
| 45 | |
| 46 | ethernet-switch@0 { |
| 47 | compatible = "micrel,ks8995m"; |
| 48 | spi-max-frequency = <1000000>; |
| 49 | reg = <0>; |
| 50 | }; |
| 51 | |
| 52 | codec@1 { |
| 53 | compatible = "ti,tlv320aic26"; |
| 54 | spi-max-frequency = <100000>; |
| 55 | reg = <1>; |
| 56 | }; |
| 57 | }; |