No WiFi with RaspberryPi 400

[andypugh]

The Pi 400 has no WiFi with the LinuxCNC RT kernel.
There are some clues here: https://archlinuxarm.org/forum/viewtopic.php?f=15&t=14868
However simply adding the bcm2711-rpi-400.dtb file as in the patch here: raspberrypi@efd0616#diff-4a31af8261f8368ab91e9d684f2664249db2cf30d499f7d439fa902c8714d04f
Isn't a simple answer as it references many files / labels that do not exist in the 4.19 kernel.

[antage]

I think that it might be difficult to fix / not worthwhile. It's probably better to start again with a 5.x kernel and realtime patch.

I have no RPi 400 and I can't do any tests. I think a key difference may be following definition:

# bcm2711-rpi-400.dts
/* uart0 communicates with the BT module */
&uart0 {
        pinctrl-names = "default";                                                                                      
        pinctrl-0 = <&uart0_ctsrts_gpio30 &uart0_gpio32>;
        uart-has-rtscts;
        status = "okay";

        bluetooth {
                compatible = "brcm,bcm43438-bt";
                max-speed = <2000000>;
                shutdown-gpios = <&expgpio 0 GPIO_ACTIVE_HIGH>;
        };
};
...

[andypugh]

That seems to be Bluetooth? Or are you saying that the WiFi is on uart0 on other Pi models?
(I didn't check whether BT works on the 400 with the new kernel)

[antage]

As far as I know BT and WiFi are in a single chip. So uart0 may control BT and WiFi.

For RPi4 the definition is different:

# bcm2838-rpi-4-b.dts
/* uart0 communicates with the BT module */
&uart0 {
        pinctrl-names = "default";
        pinctrl-0 = <&uart0_ctsrts_gpio30 &uart0_gpio32 &gpclk2_gpio43>;
        status = "okay";

        bluetooth {
                compatible = "brcm,bcm43438-bt";
                max-speed = <2000000>;
                shutdown-gpios = <&expgpio 0 GPIO_ACTIVE_HIGH>;
        };
};

It's a hypothesis. I don't know for sure.