[BUG] DM_VIDEO broken on imx6q

[Anatolij Gustschin <agust@denx.de>]

Hi,

On Sat, 1 Aug 2020 21:14:10 +0200
Soeren Moch smoch at web.de wrote:

> 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.

Thanks for debugging and reporting!

> 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?

Since the second framebuffer is not in use currently, the probing for
second ipu device is not done.

> 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)?

Yes, the later is the correct solution. I've sent a patch.

--
Anatolij