ZCU 104 - Cannot see nor configure LEDs on Buildroot

[pcotret]

I've followed this tutorial for a ZCU104 board.
According to the HOWTO, I was hoping to play with the 4 LEDs available on the board.

However, I cannot see LEDs in my Buildroot prompt:

root@buildroot:~# ls /sys/class/
bdi           graphics      mem           pps           tty
block         hwmon         misc          ptp           vc
devlink       i2c-adapter   mmc_host      pwm           vtconsole
drm           i2c-dev       mtd           spi_master
fpga_manager  input         net           spidev

LEDs are implemented in the Verilog design (I checked that to be sure).

LEDs are also visible in the device tree:

            leds: gpio@f0002800 {
                compatible = "litex,gpio";
                reg = <0xf0002800 0x4>;
                gpio-controller;
                #gpio-cells = <2>;
                litex,direction = "out";
                status = "disabled";
            };

Is the status=disabled important if I want to play with the LEDs?
How would I modify that?

[pcotret]

https://github.com/litex-hub/linux-on-litex-vexriscv/blob/master/boards.py#L206

I've added the LED capability in the boards.py Python script but it doesn't change :(

[trabucayre]

status = "disabled" means the driver will not be loaded. Could you try with status = "okay" ?

[pcotret]

Hum, I just need to understand how to re-generate the software image once this status="okay" has been manually modified.

[Rajnesh28]

@pcotret Not sure if the kernel supports overlays, but you can maybe use a device-tree overlay to override that status.

Maybe it's changed since the last time I've used this repository, but I think there's a python script that generates the device-tree source based on some platform settings, maybe you could manually change that setting, recompile with dtc and then use that for your Linux boot?

[pcotret]

@pcotret Not sure if the kernel supports overlays, but you can maybe use a device-tree overlay to override that status.

Maybe it's changed since the last time I've used this repository, but I think there's a python script that generates the device-tree source based on some platform settings, maybe you could manually change that setting, recompile with dtc and then use that for your Linux boot?

I'll give it a try when I can

[enjoy-digital]

The status = "disabled" line is not the final state of the LED node. The generated DTS first declares the LiteX GPIO node disabled, then later overrides it with:

&leds {
        litex,ngpio = <4>;
        status = "okay";
};

So please check the complete generated DTS/DTB, not only the first leds node.

Also, these LEDs are exposed as LiteX GPIOs, not as Linux LED-class devices, so /sys/class/leds is not expected. They should be accessed through /sys/class/gpio with the LiteX GPIO driver enabled.

I also updated the HOWTO to avoid the old hardcoded GPIO number and document how to find the correct LiteX GPIO base dynamically with: 5460351