Hi,
unfortunately the patch [1] is only the first part to get DM_VIDEO running properly on tbs2910 for u-boot-2020.10. With this, I get a valid video output signal, but no actual video console output, only a blank screen.
After some debugging, no with access to a HDMI monitor, the problem seems to be: imx6q has two ipu units, so DM_VIDEO creates 2 video devices. For these two devices also memory for two framebuffers is reserved in video-uclass, starting from gd->video_top downwards. Then vidconsole correctly uses the first video device (ipu1), but apparently the framebuffer from ipu2 at gd->video_bottom. So I see the empty framebuffer from ipu1 while the console output goes to the framebuffer memory of ipu2.
I guess there is the same problem on all imx6q devices with 2 ipu units, while on imx6s/6dl devices with a single ipu everything works fine. Disabling the second ipu in the tbs2910 devicetree also helps, but I think this is not a proper solution.
What should be done about this? Only probing the first ipu/video device? Assigning the framebuffer memory bottom-up? Using the assigned framebuffer memory of the active video device for console output (seems to be the correct solution, but maybe not so easy to implement)? Something else?
Thanks, Soeren
[1] https://patchwork.ozlabs.org/project/uboot/patch/20200730121157.5305-1-smoch...