ILI9340 white screen without image when using LVGL in Zephyr

Question

I have an ILI9340 connected to an nRF53 and want to use LVGL in Zephyr (NCS 2.6.1), but I got no label, etc. showing up. Instead, the display is showing a white screen.

I´m wondering about what can be wrong here. It´s similar to the examples so it should work. Can someone help me with this issue?

Thanks!

#include <zephyr/dt-bindings/display/ili9xxx.h>

/ {
	chosen {
		zephyr,display = &display;
	};
};

&pinctrl {
    spi4_default: spi4_default {
		group1 {
			psels = <NRF_PSEL(SPIM_SCK, 0, 5)>,
				    <NRF_PSEL(SPIM_MOSI, 0, 4)>;
			};
    };

    spi4_sleep: spi4_sleep {
		group1 {
			psels = <NRF_PSEL(SPIM_SCK, 0, 5)>,
				    <NRF_PSEL(SPIM_MOSI, 0, 4)>;
                    low-power-enable;
			};
    };
};

&spi4 {
    status = "okay";
    compatible = "nordic,nrf-spim";
    pinctrl-0 = <&spi4_default>;
    pinctrl-1 = <&spi4_sleep>;
    pinctrl-names = "default", "sleep";
    cs-gpios = <&gpio0 6 GPIO_ACTIVE_LOW>;

    display: ili9340@0 {
        compatible = "ilitek,ili9340";
        spi-max-frequency = <1000000>;
        reg = <0>;
        width = <240>;
        height = <320>;
		reset-gpios = <&gpio0 25 GPIO_ACTIVE_HIGH>;
		cmd-data-gpios = <&gpio0 7 GPIO_ACTIVE_HIGH>;
    };
};

#include <zephyr/kernel.h>
#include <zephyr/device.h>
#include <zephyr/logging/log.h>
#include <zephyr/drivers/display.h>

#include <lvgl.h>

#include <stdio.h>
#include <string.h>

LOG_MODULE_REGISTER(app);

static lv_obj_t *root_screen;
static lv_obj_t *hello_world_label;
static const struct device *display_dev = DEVICE_DT_GET(DT_CHOSEN(zephyr_display));

int main(void)
{
    if(!device_is_ready(display_dev)) {
        LOG_ERR("Display not ready!");
		return -1;
    }
display_blanking_off(display_dev);
	root_screen = lv_scr_act();
	hello_world_label = lv_btn_create(root_screen);
	lv_label_set_text(hello_world_label, "Hello world!");
	lv_obj_align(hello_world_label, LV_ALIGN_CENTER, 0, 0);

	while(1) {
		LOG_ERR("Done");
		k_msleep(100);
	}
}

CONFIG_HEAP_MEM_POOL_SIZE=32000
CONFIG_MAIN_STACK_SIZE=2048

CONFIG_SPI=y
CONFIG_DISPLAY=y
CONFIG_DISPLAY_LOG_LEVEL_ERR=y

CONFIG_LOG=y

CONFIG_DEBUG_OPTIMIZATIONS=y
CONFIG_USE_SEGGER_RTT=y
CONFIG_LOG_BACKEND_RTT=y
CONFIG_LOG_BACKEND_RTT_MODE_BLOCK=y
CONFIG_LOG_BUFFER_SIZE=4096
CONFIG_LOG_BACKEND_RTT_OUTPUT_BUFFER_SIZE=128
CONFIG_LOG_BLOCK_IN_THREAD=y

CONFIG_LVGL=y
CONFIG_LV_USE_LOG=y
CONFIG_LV_Z_FLUSH_THREAD=y
CONFIG_LV_Z_FLUSH_THREAD_PRIO=0
CONFIG_LV_Z_MEM_POOL_SIZE=128000