Hello. I have trouble trying to get information from DT in my kernel module.
I made and built device tree overlay similar to one for spidev kernel
module. Here it is:
/dts-v1/;
/plugin/;
/ {
compatible = "ti,beaglebone", "ti,beaglebone-black";
/* identification */
part-number = "BB-ARDUINO-ECHO";
version = "00A0";
fragment@0 {
target = <&am33xx_pinmux>;
__overlay__ {
spi0_pins_s0: spi0_pins_s0 {
pinctrl-single,pins = <
0x150 0x30 /* mcasp0_aclkx.spi0_sclk, INPUT_PULLUP | MODE0 */
0x154 0x30 /* mcasp0_fsx.spi0_d0, INPUT_PULLUP | MODE0 */
0x158 0x10 /* mcasp0_axr0.spi0_d1, OUTPUT_PULLUP | MODE0 */
0x15c 0x10 /* mcasp0_ahclkr.spi0_cs0, OUTPUT_PULLUP | MODE0 */
>;
};
};
};
fragment@1 {
target = <&spi0>;
__overlay__ {
#address-cells = <1>;
#size-cells = <0>;
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&spi0_pins_s0>;
ardiuno_echo@0 {
compatible = "arduino,pro-mini-spi-generic";
reg = <0>;
spi-max-frequency = <100000>;
};
};
};
};
And here I trying to access spi-max-frequency property from my probe()
function of device driver:
static int spi_protocol_generic_probe(struct spi_device *spi)
{
int err, ret;
int devData = 0;
const struct of_device_id *match;
struct device_node *of_target_node;
u32 max_speed_arduino = 0;
const char *of_compt_str = kcalloc(sizeof(char), 255, GFP_KERNEL);
__spi_device_internal = spi;
default_values.speed_hz = spi->max_speed_hz;
default_values.mode = spi->mode;
default_values.bits_per_word = spi->bits_per_word;
debug_printk("spi-protocol-generic: default speed is %d Hz\n",
default_values.speed_hz);
// check and read data from of_device_id...
match = of_match_device(spi_protocol_generic_of_match, &spi->dev);
if (!match) {
debug_printk("device not found in device tree...\n");
return -1;
}
of_target_node = of_find_compatible_node(NULL, NULL, match->compatible);
if (!of_target_node) {
of_node_put(of_target_node);
debug_printk("no compatible devices in DT!\n");
}
// Here we can use of_get_property, but I prefer more readable
// code insted of mire obvious
ret = of_property_read_u32(of_target_node, "spi-max-frequency",
&max_speed_arduino);
if (ret) {
debug_printk("cannot find property in DT node, status %d\n",
ret);
return ret;
} else {
debug_printk("freq is %x Hz\n", max_speed_arduino);
}
spi->bits_per_word = 8;
spi->mode = SPI_MODE_0;
spi->max_speed_hz = max_speed_arduino;
err = spi_setup(spi);
if (err < 0) {
printk(KERN_DEBUG "spi-protocol-generic: spi_setup failed!\n");
return err;
} else {
printk(KERN_DEBUG "spi-protocol-generic: now speed is %d Hz\n",
spi->max_speed_hz);
}
// ... and so on ...
}
I can access other properties such as reg and compatible. But even if I am
trying to get the property of DT from sysfs, this property seems to have
invalid value.
For example, if I set spi-max-frequency to 1000000 (1 MHz), value from
sysfs will be invalid and it won't equal 1000000. This value is not
depending from my value in DT overlay.
How can I set this property correctly?
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