I made a discovery (for me) which I don't really understand:
I have a custom i.MX6 Board with a i.MX6Solo connected to a 24-Bit RGB display.
I'm running a 4.19.26 Mainline Linux-Kernel on it and configured it with the device tree attched to this message (graphic.dtsi).
The I displayed some color gradients on it (attached All-Colors-800x480.png).
But the color gradients don't look as smooth as a 24Bit-color display should look like, they are very visible graded.
So I meassured the output signals and wondered what I saw:
The lowest bits R0, R1 and R2 are copies of the highest bits R5, R6 and R7. On blue it's the same.
On green only G0 and G1 are copies of higher bits.
So my colors seem to be reduced to RGB565.
Is there something wrong with the IPU-Driver? Am I configuring it the wrong way? How can I enable real 24bit colors?