Since 3.x kernel version in order to set a different LVDS panel resolution a device tree file modification is required.
The file which should be modified is arch/arm64/boot/dts/imx8qxp-qx8x.dtsi under the kernel root folder, into &ldb1 section, in particular display-timings
<details>
<summary>The default version looks like this (click here)</summary>
| Code Block | ||
|---|---|---|
| ||
&ldb1 {
status = "okay";
lvds-channel@0 {
fsl,data-mapping = "spwg";
fsl,data-width = <18>;
primary;
status = "okay";
display-timings {
native-mode = <&timing0>;
timing0: hsd100pxn1 {
clock-frequency = <65000000>;
hactive = <1024>;
vactive = <768>;
hback-porch = <220>;
hfront-porch = <40>;
vback-porch = <21>;
vfront-porch = <7>;
hsync-len = <60>;
vsync-len = <10>;
};
};
};
lvds-channel@1 {
fsl,data-mapping = "spwg";
fsl,data-width = <18>;
status = "okay";
display-timings {
native-mode = <&timing1>;
timing1: hsd100pxn1 {
clock-frequency = <65000000>;
hactive = <1024>;
vactive = <768>;
hback-porch = <220>;
hfront-porch = <40>;
vback-porch = <21>;
vfront-porch = <7>;
hsync-len = <60>;
vsync-len = <10>;
};
};
};
}; |
</details>
Check if the panel is 18 or 24 bit, and change fsl,data-width = <18>; if needed.
As an example here you can find values for some different resolutions
<details>
<summary>800x480 (click here)</summary>
| Code Block | ||
|---|---|---|
| ||
clock-frequency = <33000000>;
hactive = <800>;
vactive = <480>;
hback-porch = <56>;
hfront-porch = <50>;
vback-porch = <20>;
vfront-porch = <53>;
hsync-len = <180>;
vsync-len = <30>; |
</details>
<details>
<summary>800x600 (click here)</summary>
| Code Block | ||
|---|---|---|
| ||
clock-frequency = <40000000>;
hactive = <800>;
vactive = <600>;
hfront-porch = <88>;
hback-porch = <72>;
hsync-len = <64>;
vback-porch = <15>;
vfront-porch = <4>;
vsync-len = <6>;
hsync-active = <2>;
vsync-active = <2>; |
</details>
<details>
<summary>1024x600 (click here)</summary>
| Code Block | ||
|---|---|---|
| ||
clock-frequency = <45000000>;
hactive = <1024>;
vactive = <600>;
hback-porch = <50>;
hfront-porch = <50>;
vback-porch = <10>;
vfront-porch = <10>;
hsync-len = <76>;
vsync-len = <5>; |
</details>
<details>
<summary>1024x768 (click here)</summary>
| Code Block | ||
|---|---|---|
| ||
clock-frequency = <65000000>;
hactive = <1024>;
vactive = <768>;
hback-porch = <220>;
hfront-porch = <40>;
vback-porch = <21>;
vfront-porch = <7>;
hsync-len = <60>;
vsync-len = <10>;
vsync-len = <4>; |
</details>
<details>
<summary>1280x800 (click here)</summary>
| Code Block | ||
|---|---|---|
| ||
clock-frequency = <71000000>;
hactive = <1280>;
vactive = <800>;
hback-porch = <40>;
hfront-porch = <40>;
vback-porch = <10>;
vfront-porch = <3>;
hsync-len = <80>;
vsync-len = <10>; |
</details>
<details>
<summary>1368x768 (click here)</summary>
| Code Block | ||
|---|---|---|
| ||
clock-frequency = <72000000>;
hactive = <1368>;
vactive = <768>;
hback-porch = <93>;
hfront-porch = <33>;
vback-porch = <22>;
vfront-porch = <7>;
hsync-len = <40>;
vsync-len = <4>; |
</details>
<details>
<summary>1920x1050 (click here)</summary>
| Code Block | ||
|---|---|---|
| ||
clock-frequency = <110000000>;
hactive = <1920>;
vactive = <1050>;
hback-porch = <40>;
hfront-porch = <80>;
vback-porch = <15>;
vfront-porch = <15>;
hsync-len = <40>;
vsync-len = <5>; |
</details>
<details>
<summary>1920x1080 (click here)</summary>
| Code Block | ||
|---|---|---|
| ||
clock-frequency = <130000000>;
hactive = <1920>;
vactive = <1080>;
hback-porch = <100>;
hfront-porch = <40>;
vback-porch = <30>;
vfront-porch = <2>;
hsync-len = <10>;
vsync-len = <2>; |
</details>
After saving the changes made into the device tree file, it should be recompiled and transferred to the target system (instructions under Kernel standalone)
Before plugging in the panel, the jumper settings on the conga-QEVAL/Qseven 2.0 should be properly set (X46, X47, X50).
Also is highly recommendable measure the signals on connector X41
Pin 16: 1st channel clock
Ping 30: 2nd channel clock