ad7380 driver failed to load

[jwittke]

I am using one of the newer Raspberry Pi Linux kernel branches:

# uname -r
6.15.11-v8

On a Raspberry Pi 4 Model B Rev 1.4,
with the ad7380 iio driver from the Analog Linux branch rpi-6.12.y using the newest ad7380.c (ddd1c08).

When using a overlay like this:

// SPDX-License-Identifier: GPL-2.0
/dts-v1/;
/plugin/;

/ {
        compatible = "brcm,bcm2835";

        fragment@0 {
                target-path = "/";
                __overlay__ {
                        supply_3_3V: fixedregulator@0 {
                                compatible = "regulator-fixed";
                                regulator-name = "fixed-supply";
                                regulator-min-microvolt = <3300000>;
                                regulator-max-microvolt = <3300000>;
                                regulator-boot-on;
                        };
                };
        };


        fragment@1 {
                target = <&spi0>;
                __overlay__ {
                        #address-cells = <1>;
                        #size-cells = <0>;
                        status = "okay";

                        ad7386-4@0 {
                                compatible = "adi,ad7386-4";
                                reg = <0>;
                                spi-max-frequency = <8000000>;
                                spi-cpol;
                                spi-cpha;
                                vcc-supply = <&supply_3_3V>;
                                vlogic-supply = <&supply_3_3V>;
                        };
                };
        };

        fragment@2 {
                target = <&spidev0>;
                __overlay__ {
                        status = "disabled";
                };
        };
};

I can't correctly load the driver while attached the EVAL-AD7386-4 to the Raspberry using the correct SPI gpio pins.

Reading the kernel messages i get:

$ dmesg

[ 5.830845] ad7380 spi0.0: probe with driver ad7380 failed with error -22

I traced the error with printk in the module to the ad7380_init function when the driver wants to
do a hard reset using the regmap regmap_update_bits.

Is it a fault in the SPI communication? How can I check this?