i.MX8QM Display Controller loopback to ISI, kernel 5.4.y

[#1]

BSP: L5.4.47-2.2.0-rc2

Board: imx8QM B0

HW:  LVDS2HDMI , MIPIDSI2HDMI.

It is the porting of i.MX8QM dpu loopback to isi. to the 5.4.y, with the addition of the MIPI-DSI loopback and the HDMI loopback. 

Overview of the DC capture configuration:

For enabling the capture:

• only DC 0 Stream 0  and DC 1 Stream 1 can be captured
• The pixel link Master address should be set to 3 because the Receiver Address at ISI is 3 and can't be changed.
• To continue displaying the stream, the Receiver Address at LVDS and DSI or HDMI should be changed to 3. It is possible to change the RA by using GPIO of the modules.

Patches:

Create V4L2 device enabling the capture of by the ISI of DC loop-backs.

1. Enable ISI capture from DSI 0 / LVDS 1 in 1920x1080 (at the same time.)
2. Enable ISI capture from HDMI in 2840x2160 (half with even pixel) in 1920x2160.

While capturing with the ISI, the captured screen continue to be displayed.

Remark: Ov5640 cameras are also enabled in the same dtb. So 4 stream in 1920x1080 can be captured at the same time.

Installation and gstreamer command:

See readme