While I compile DTS for my device, it gives me warnings, that don't really make sense to me. There are two spi-chips on my device, their description is DTS is the following:
spi-gpio {
compatible = "spi-gpio";
#address-cells = <0x1>;
ranges;
status = "okay";
sck-gpios = <&pio 4 9 GPIO_ACTIVE_HIGH>; // PE9
mosi-gpios = <&pio 4 6 GPIO_ACTIVE_HIGH>; // PE6
miso-gpios = <&pio 4 8 GPIO_ACTIVE_HIGH>; // PE8
cs-gpios = <&pio 4 4 GPIO_ACTIVE_HIGH>, // PE4
<&pio 4 17 GPIO_ACTIVE_HIGH>; // PE17
num-chipselects = <2>;
/* Clients */
m90e32@0 {
reg = <0>;
compatible = "atmel,m90e32";
spi-max-frequency = <1000>;
reset-gpios = <&pio 4 18 GPIO_ACTIVE_HIGH>; // PE17
};
m90e32@1 {
reg = <1>;
compatible = "atmel,m90e32";
spi-max-frequency = <1000>;
reset-gpios = <&pio 4 18 GPIO_ACTIVE_HIGH>; // PE17
};
};
The warnings are:
Warning (reg_format): /spi-gpio/m90e32@0:reg: property has invalid length (4 bytes) (#address-cells == 1, #size-cells == 1)
Warning (reg_format): /spi-gpio/m90e32@1:reg: property has invalid length (4 bytes) (#address-cells == 1, #size-cells == 1)
I've read documentation for DTS and I've seen a similar question on SO, but it' doesn't really suit my situation. What am I missing?
In general, the reg property encodes an arbitrary number of (address, length) pairs. The number of <u32> cells required to encode each pair is given by the sum of the #address-cells and #size-cells properties in the parent node. The first #address-cells number of cells encodes the address, and the remaining #size-cells number of cells encodes the length, both in big-endian byte order.
If #address-cells is not specified in the parent node, it defaults to 2.
If #size-cells is not specified in the parent node, it defaults to 1.
The #size-cells property can be set to 0 in the parent node to omit the length from each (address, length) pair.
SPI and I2C devices only have a single-cell address1, and do not have a length, so the parent (controller) node should specify #address-cells=1; #size-cells=0;. Also, the ranges property in an SPI or I2C controller node has no effect on the child device nodes and can be omitted.
spi-gpio {
compatible = "spi-gpio";
#address-cells = <0x1>;
#size-cells = <0x0>;
status = "okay";
sck-gpios = <&pio 4 9 GPIO_ACTIVE_HIGH>; // PE9
mosi-gpios = <&pio 4 6 GPIO_ACTIVE_HIGH>; // PE6
miso-gpios = <&pio 4 8 GPIO_ACTIVE_HIGH>; // PE8
cs-gpios = <&pio 4 4 GPIO_ACTIVE_HIGH>, // PE4
<&pio 4 17 GPIO_ACTIVE_HIGH>; // PE17
num-chipselects = <2>;
/* Clients */
m90e32@0 {
reg = <0>;
compatible = "atmel,m90e32";
spi-max-frequency = <1000>;
reset-gpios = <&pio 4 18 GPIO_ACTIVE_HIGH>; // PE17
};
m90e32@1 {
reg = <1>;
compatible = "atmel,m90e32";
spi-max-frequency = <1000>;
reset-gpios = <&pio 4 18 GPIO_ACTIVE_HIGH>; // PE17
};
};
1 Actually, SPI devices can have more than one address, but each address is encoded as single <u32> address cell with no length cell following it.