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Simon Glass623b6382014-10-13 23:42:00 -06001Soft SPI
2
3The soft SPI bus implementation allows the use of GPIO pins to simulate a
4SPI bus. No SPI host is required for this to work. The down-side is that the
5performance will typically be much lower than a real SPI bus.
6
7The soft SPI node requires the following properties:
8
9compatible: "u-boot,soft-spi"
10soft_spi_cs: GPIO number to use for SPI chip select (output)
11soft_spi_sclk: GPIO number to use for SPI clock (output)
12soft_spi_mosi: GPIO number to use for SPI MOSI line (output)
13soft_spi_miso GPIO number to use for SPI MISO line (input)
14spi-delay-us: Number of microseconds of delay between each CS transition
15
16The GPIOs should be specified as required by the GPIO controller referenced.
17The first cell holds the phandle of the controller and the second cell
18typically holds the GPIO number.
19
20
21Example:
22
23 soft-spi {
24 compatible = "u-boot,soft-spi";
25 cs-gpio = <&gpio 235 0>; /* Y43 */
26 sclk-gpio = <&gpio 225 0>; /* Y31 */
27 mosi-gpio = <&gpio 227 0>; /* Y33 */
28 miso-gpio = <&gpio 224 0>; /* Y30 */
29 spi-delay-us = <1>;
30 #address-cells = <1>;
31 #size-cells = <0>;
32 cs@0 {
33 };
34 };