Hi There!
We try to have a second HDMI output for our IMX8QM Custom Carrier port and plan to use the LT8912 MIPI-DSI 2 HDMI bridge for this.
I have seen that something similar has already been done with the imx8 Colibri. So I went and took some parts from the fsl-imx8qxp-colibri-dshdmi-eval-v3.dts and put it in our device tree:
&i2c3 {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_lpi2c3>;
#address-cells = <1>;
#size-cells = <0>;
clock-frequency = <100000>;
status = "okay";
rtc_i2c: rtc@68 {
compatible = "st,m41t0";
reg = <0x68>;
};
lt8912@48 {
compatible = "lontium,lt8912";
reg = <0x48>;
port {
lt8912_1_in: endpoint {
remote-endpoint = <&mipi_dsi_bridge1_out>;
};
};
display-timings {
native-mode = <&timing1>;
timing0: timing0 {
clock-frequency = <74250000>;
hactive = <1280>;
vactive = <720>;
hfront-porch = <110>;
hsync-len = <40>;
hback-porch = <220>;
vfront-porch = <5>;
vsync-len = <5>;
vback-porch = <20>;
hsync-active = <0>;
vsync-active = <0>;
de-active = <0>;
pixelclk-active = <0>;
};
timing1: timing1 {
clock-frequency = <148500000>;
hactive = <1920>;
vactive = <1080>;
hfront-porch = <88>;
hsync-len = <44>;
hback-porch = <148>;
vfront-porch = <36>;
vsync-len = <5>;
vback-porch = <4>;
hsync-active = <0>;
vsync-active = <0>;
de-active = <0>;
pixelclk-active = <0>;
};
};
};
The driver was already activated in the kernel. It also looks like the driver is working, as I get no errors and the i2c bus shows the addresses as used (0x48 … 0x4b):
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- UU UU UU UU -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- UU -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --
But I am still missing the part where to tell the system to output something on the HDMI. I have seen in the colibri device tree that this is mapped to the mipi lvds0, put this is where my device tree knowledge ends and I do not know to rework it for the IMX8QM Apalis.
So my question is, do you have some sample code or some hints on how to get the MIPI-DSI To HDMI bridge working on the IMX8QM?
Thanks!
Best Regards,
Florian