STM32H735G Disco , LVGL,LTDC and Octospi RAM

[Leowep1]

I am trying to implement a frame buffer in the hyperrRAM (acces via OctoSPI) of my board because there is not enough internal RAM in the STM32H735IGK.
I've been using the graphical library LVGL for the display. I'm able to use the display with it but however when I reduce the size of my screen from 480x272 to 360x160.
However, when I try to put my frame buffer on the HyperRAM the screen goes dark in the region of the display I'm trying to use. I don't know if it 's a problem on how I added the HyperRam on the device tree or if the problem is somewhere else.

LTDC and hyperRAM devicetree

#include <st/h7/stm32h735igkx-pinctrl.dtsi>


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

&pinctrl {
	/omit-if-no-ref/ ltdc_vsync_pa4: ltdc_vsync_pa4 {
		pinmux = <STM32_PINMUX('A', 4, AF14)>;
	};
};

&octospi2 {
	pinctrl-0 = <&octospim_p2_clk_pf4 &octospim_p2_ncs_pg12  	      
	&octospim_p2_io0_pf0 &octospim_p2_io1_pf1
	&octospim_p2_io2_pf2 &octospim_p2_io3_pf3
	&octospim_p2_io4_pg0 &octospim_p2_io5_pg1
	&octospim_p2_io6_pg10 &octospim_p2_io7_pg11
	&octospim_p2_dqs_pf12
	>;	    
	pinctrl-names = "default";
	status = "okay";

	chip_hyperram: chip_hyperram@70000000 {
		status = "okay";
		compatible = "st,stm32-ospi-psram";
		reg = <0x70000000 DT_SIZE_M(16)>;
		size = <DT_SIZE_M(128)>;
		max-frequency = <DT_FREQ_M(100)>;
		fixed-latency;
		burst-length = <3>;
		st,csbound = <10>;
		st,refresh = <320>;
		#address-cells = <1>;
		#size-cells = <1>;
		hyperram: hyperram@70000000 {
		    compatible = "zephyr,memory-region";
		    status = "okay";
		    reg = <0x70000000 DT_SIZE_M(16)>;
		    zephyr,memory-region = "HYPERRAM";
		    zephyr,memory-attr = <DT_MEM_ARM(ATTR_MPU_RAM_NOCACHE)>;
		};
	};
};



&ltdc {
    status = "okay";
    reg = < 0x50001000 0x200 >;
    width = <360>;
    height = <160>;
    interrupts = < 0x58 0x0 >,
	     	< 0x59 0x0 >;
    interrupt-names = "ltdc",
	              	  "ltdc_er"; 
    ext-sdram = <&hyperram>;
    pixel-format = <PANEL_PIXEL_FORMAT_RGB_888>; // RGB_888
	pinctrl-0 = <&ltdc_r0_pe0 &ltdc_r1_ph3 &ltdc_r2_ph8 &ltdc_r3_ph9 
		         &ltdc_r4_ph10 &ltdc_r5_ph11 &ltdc_r6_pe1 &ltdc_r7_pe15 
		         &ltdc_g0_pb1 &ltdc_g1_pb0 &ltdc_g2_pa6 &ltdc_g3_pe11
		         &ltdc_g4_ph15 &ltdc_g5_ph4 &ltdc_g6_pc7 &ltdc_g7_pd3
		         &ltdc_b0_pg14 &ltdc_b1_pd0 &ltdc_b2_pd6 &ltdc_b3_pa8
		         &ltdc_b4_pe12 &ltdc_b5_pa3 &ltdc_b6_pb8 &ltdc_b7_pb9
		         &ltdc_de_pe13 &ltdc_clk_pg7 &ltdc_hsync_pc6 &ltdc_vsync_pa4
		        >;
	pinctrl-names = "default";
	disp-on-gpios = <&gpiod 10 GPIO_ACTIVE_HIGH>;
    def-back-color-red = < 0xff >;                                                                                 
    def-back-color-green = < 0xff >;                                                                               
    def-back-color-blue = < 0xff >;     

    display-timings {
        compatible = "zephyr,panel-timing";
        de-active = <0>;
		pixelclk-active = <0>;
		hsync-active = <1>;
		vsync-active = <1>;
        hsync-len = <41>;
        hback-porch = <13>;
        hfront-porch = <32>;
        vsync-len = <10>;
        vback-porch = <2>;
        vfront-porch = <2>;
    };

};


&pll3 {
	div-m = <5>;
	mul-n = <192>;
	div-p = <2>;
	div-q = <20>;
	div-r = <99>;
	clocks = <&clk_hse>;
	status = "okay";
};