2353061_en-US

[#1]

LVDS channel disabled albeit enabled in device tree

I am working with a 8MPLUSLPD4-EV building the OS stack with the latest Yocto Project meta-freescale layer (LAYERSERIES_COMPAT_freescale-layer = "whinlatter wrynose").

I am looking to use the IMX-LVDS-HDMI adapter board.

The default device tree imx8mp-evk.dts should correctly enable lvds-channel0 for use with this board and the it6263 chip. This is what is in the device tree file:

&ldb {
        status = "okay";

        lvds-channel@0 {
                status = "okay";

                port@1 {
                        reg = <1>;

                        lvds_out: endpoint {
                                remote-endpoint = <&it6263_in>;
                        };
                };
        };
};

However, when I boot the board:

# dmesg | grep it6263
[    2.998982] it6263 1-004c: Probe failed. Remote port 'lvds-channel@0' disabled
# cat /sys/firmware/devicetree/base/ldb-display-controller/lvds-channel\@0/status 
disabled
# cat /sys/firmware/devicetree/base/ldb-display-controller/status                 
okay

Albeit the device tree explicitly enables lvds-channel@0 it is being disabled somewhere, although the ldb-display-controller itself is enabled.

The bootloader is u-boot-imx-2025.04. The source file arch/arm/mach-imx/imx8m/soc.c contains the function disable_lvds_lcdif_nodes() which disables the lvds channels by patching the device tree for certain variants of the SoC, namely: imx8mpul, imx8mpsc, imx8mpdsc.

I am wondering why this would happen on the 8MPLUSLPD4-EV as the SoC should be an imx8mp quad.

Re: LVDS channel disabled albeit enabled in device tree

Hello,

I tried on my side with the pre-built image we have on the EVK, it is working correctly even I see that the port shows as okay

root@imx8mpevk:~# cat /sys/firmware/devicetree/base/ldb-display-controller/lvds-channel@0/status
okay

I'm building using yocto now just to verify as well, but pre-built is essentially the same so I do not expect a different result.

Best regards/Saludos,
Aldo.

Re: LVDS channel disabled albeit enabled in device tree

Thank you, @AldoG. Much appreciated. Please let me know what you find.

I have decompiled the dtb and the node is enabled in the dtb:

        ldb-display-controller {
                #address-cells = <0x01>;
                #size-cells = <0x00>;
                compatible = "fsl,imx8mp-ldb";
                clocks = <0x02 0x149>;
                clock-names = "ldb";
                assigned-clocks = <0x02 0xae>;
                assigned-clock-parents = <0x02 0x28>;
                gpr = <0x5d>;
                power-domains = <0x63>;
                status = "okay";
                phandle = <0x11c>;

                lvds-channel@0 { 
                        #address-cells = <0x01>;
                        #size-cells = <0x00>;
                        reg = <0x00>;
                        phys = <0x8a>; 
                        phy-names = "ldb_phy";
                        status = "okay";

                        port@0 {
                                reg = <0x00>;

                                endpoint {
                                        remote-endpoint = <0x8b>;
                                        phandle = <0x61>;
                                };
                        };

                        port@1 {
                                reg = <0x01>;

                                endpoint {
                                        remote-endpoint = <0x8c>;
                                        phandle = <0x36>;
                                };
                        };
                };

                lvds-channel@1 {
                        reg = <0x01>;
                        phys = <0x8d>;
                        phy-names = "ldb_phy";
                        status = "disabled";

                        port {

                                endpoint {
                                        remote-endpoint = <0x8e>;
                                        phandle = <0x62>;
                                };
                        };
                };
        };

It seems that u-boot is changing the device tree. However, it is not clear to me why.

This is the YP build configuration:

Build Configuration:
BB_VERSION           = "2.16.0"
BUILD_SYS            = "x86_64-linux"
NATIVELSBSTRING      = "universal"
TARGET_SYS           = "aarch64-tdx-linux"
MACHINE              = "imx8mp-lpddr4-evk"
SDKMACHINE           = "x86_64"
DISTRO               = "test"
DISTRO_VERSION       = "0.0.0-devel-20260417002956+build.0"
TUNE_FEATURES        = "aarch64 crc cortexa53 crypto"
meta-clang           = "master:78c5e12f08198f4f257a9348516d2103cd617c1d"
meta-freescale       = "master:4cc4bc05063f7f4c105587332493742379d11ad7"
meta-freescale-3rdparty = "master:29c36ae80ba5762091f48d6d15b637455cc15758"
meta-freescale-distro = "master:70b7591ecaa99cb6366f93ee05df7c38d94d724b"
meta-filesystems     
meta-multimedia      
meta-networking      
meta-oe              
meta-perl            
meta-python          = "master:44a29c54f9b6e87431e34de1558a962d0e614ef8"
meta-qt6             = "6.11:34ad7dbc591a5cf31f6d23799c339ba8985f1428"
meta-efi-secure-boot 
meta-encrypted-storage 
meta-ids             
meta-integrity       
meta-secure-core-common 
meta-signing-key     
meta-tpm2            = "master:a9c1ce8beea586ee6837284d922e45e4441f09f6"
meta-security        
meta-poky            
meta-yocto-bsp       = "master:49cbb01d52521bfe557395c9ebfae6b1c162581e"
meta                 = "master:274ce0c0d73fd82b63c522580aed9dbac51ba09c"