LAN969x SPI

1. LAN969x SPI

1.1. SoC Resources

LAN969X SoC have 4 FLEXCOMs (Flexible Serial Communication Controller). In order to use flexcom SPI interface, a specific flexcom should be configured in SPI mode.

1.2. Kernel configurations

Following kernel config options should be enabled to use LAN969x flexcom SPI interface:

  • CONFIG_SPI_ATMEL - SPI driver config option.

  • CONFIG_MTD, CONFIG_MTD_SPI_NOR or CONFIG_MTD_SPI_NAND based on NOR/NAND flash present.

1.3. Devicetree Configuration

To use Flexcom SPI interface, following configurations are required in device tree.

  • Each of the flexcom flx0, flx1, flx2 and flx3 nodes can be configured in SPI mode ATMEL_FLEXCOM_MODE_SPI to use SPI interface.

  • compatible string must be set to atmel,at91rm9200-spi.

  • reg property must be set with register address and length as <0x400 0x200>.

  • GPIO pins for TXD, RXD and SCK should be configured to pinctrl-0 property. Also add cs0 and cs1 pins, if present. List of possible pin mappings are as in below table:

FLEXCOM ID ALT Mode SCK pin RXD pin TXD pin

flx0

ALT 2

GPIO2

GPIO3

GPIO4

flx2

ALT 3

GPIO14

GPIO15

GPIO16

flx1

ALT 2

GPIO27

GPIO28

GPIO29

flx3

ALT 2

GPIO54

GPIO55

GPIO56

flx2

ALT 1

GPIO64

GPIO65

GPIO66

  • interrupts property must set with interrupt details. Interrupt number[CPU INTR] corresponding to a flexcom must be configured as defined in below table:

FLEXCOM ID Shared Peripheral Interrupt CPU INTR

flx0

78

46

flx1

79

47

flx2

80

48

flx3

81

49

Note that Shared peripheral interrupt lines start at index ID32. So, CPU INTR must be calculated as [Shared peripheral interrupt number - 32].

  • Input clock clocks property must be set to &fabric_clk. Note that Fabric clock (250Mhz) is clock used by AXI, AHB fabric and APB bridges which connects all th peripherals.

  • clock-names must be set to spi_clk.

  • dmas must be set to phandle dma0 and Peripheral ID as listed below:

FLEXCOM ID Tx channel PerID Rx channel PerID

flx0

3

2

flx1

3

2

flx2

7

6

flx3

9

8

1.3.1. References

1.3.2. Example

Following example explains how a flexcom SPI should be defined in DT to use a DPLL device.

&flx2 {
	atmel,flexcom-mode = <ATMEL_FLEXCOM_MODE_SPI>;
	status = "okay";

	spi2: spi@400 {
		pinctrl-0 = <&fc2_pins>;
		pinctrl-names = "default";
		cs-gpios = <&gpio 63 GPIO_ACTIVE_LOW>;
		status = "okay";

		spi@0 {
			compatible = "mchp,synce_dpll";
			reg = <0>;
			spi-max-frequency = <8000000>;
		};
	};
};

&gpio {
	fc2_pins: fc2-pins {
		pins = "GPIO_64", "GPIO_65", "GPIO_66";
		function = "fc";
	};

1.4. UserSpace

A SPI device like the DPLL shown above will be listed in the sysfs like this:

# cat /sys/bus/spi/devices/spi0.0/modalias
spi:synce_dpll