I tried to attach the video that shows the issue, but it failed.
So here is my dropbox link:
https://www.dropbox.com/s/ekb1qt6ncfxdn36/20171019_214555.mp4?dl=0

I did some investigation and it seems to be a bandwith issue.
I've rebased following patch series on current (todays) drm-tip:
https://patchwork.freedesktop.org/series/28536

You can find the branch here: (I applied the patches with std patch, so I lost author information, I added the original author with the signed-off tag, not sure if this is the right thing to do, it's only for discussion anyway)
https://github.com/a1rwulf/drm-tip/commits/yuv420

It didn't work out and my system never switched to 4:2:0 until I tried this commit:
https://github.com/a1rwulf/drm-tip/commit/45998e4d79aa20a31594143a3a053279fa52ab87

According to my dmesg output something seems wrong, though (yuv420_dmesg.log).
But this fixes the blackscreen flickering.

I'd really like to see progress with this yuv 4:2:0 mode as it seems to fix a big issue for many Intel NUC users that want to use it as a HTPC and have a GUI running in 4k@60.

Created attachment 135379 [details]
YUV 4:2:0 dmesg

First of all. Sorry about spam.
This is mass update for our bugs. 

Sorry if you feel this annoying but with this trying to understand if bug still valid or not.
If bug investigation still in progress, please ignore this and I apologize!

If you think this is not anymore valid, please comment to the bug that can be closed.
If you haven't tested with our latest pre-upstream tree(drm-tip), can you do that also to see if issue is valid there still and if you cannot see issue there, please comment to the bug.

This is still relevant.
I've tested with drm-tip recently and it is still the case.

HI,
so you are expecting series of: https://patchwork.freedesktop.org/series/36068/ to land to drm-tip?

At least this seems to fix the black screen flickering for me (tried to explain it in my early comments on this issue).
However I don't know if anyone can answer why 4k@60 doesn't work with YUV 4:4:4.

(In reply to Wolfgang Haupt from comment #7)
> At least this seems to fix the black screen flickering for me (tried to
> explain it in my early comments on this issue).
> However I don't know if anyone can answer why 4k@60 doesn't work with YUV
> 4:4:4.

The usual suspect is the cable, connectors, dongles etc.

Even though this series provides the infrastructure for YCBCR444, there is no interface for user (like a drm_property) to select its preference of YCBCR444 over RGB. We had tried to add this property during HDMI 2.0 enabling but we realized that it was not mapping to the long term goal of HDR pipeline support. So, to summarize, modeset picks RGB output by default.

In case of LSPCON based YCBCR 4:2:0 outputs, we run pipe at YCBCR 4:4:4 config, and then LSPCON scales it down to 4:2:0 sub-sampling, and that's where we need the infrastructure.

So in order to support YCBCR 4:4:4 outputs, we need a drm_property which picks user's preference between RGB/YCBCR444. 

- Shashank

Sorry maybe I'm not aware of all the technical aspects, if you say normal behaviour is RGB444, then this means my problem is actually black screen flickering with RGB444 as well.

Please note that I tried cables of 3 different manufacturers and I don't use any dongles.
My NUC is directly connected to the TV and there's several people that have this issue with kaby lake NUC's.

What is your version of LSPCON FW? 
Can you provide: cat /sys/kernel/debug/dri/0/i915_display_info

I'm on lspcon 1.72

Created attachment 139137 [details]
displayinfo

Jani, Shashank, Ville. Any help here?

Would it be possible to share the monitor's edid in text format ?

- Shashank

Created attachment 139400 [details]
edid-decode

(In reply to Wolfgang Haupt from comment #17)
> Created attachment 139400 [details]
> edid-decode

Always raw binary/hex please. We don't want to be at the mercy of the decode tool as those may have bugs or missing features.

Created attachment 139409 [details]
EDID binary

Created attachment 139410 [details]
lg hex

Ville, Shashank, could you have a look at Wolfgang's EDID?

Hi Wolfgang Haupt,

Can you please update the MCA fw to 1.75, you are still using the older version? 

Since YCBCR 420/444 series is recently merged https://patchwork.freedesktop.org/series/50897/ this issue shouldn't be there. 

Even if the issue persists with latest kernel and after updating the fw, we will take next steps.

No response for more than two months, priority of this bug is changed to medium.

Wolfgang, are you able to reproduce the issue with latest FW 1.75?

(In reply to Lakshmi from comment #23)
> No response for more than two months, priority of this bug is changed to
> medium.
> 
> Wolfgang, are you able to reproduce the issue with latest FW 1.75?

Hey Lakshmi,
Sorry for the silence, it's a pita for me to actually even the the latest FW 1.75 on my box, cause there's afaik no way to flash it without trashing the linux system, install windows and install my distro again.

I have a super busy time the next 2-3 weeks, so I'm not exactly sure if I can retest during this timeframe.
I'll come back to you asap with my results.

Hi,

I've installed windows on my nucs now to do the update.
But in the downloadcenter the latest fw for lspcon is 1.72.
Where can I find 1.75?

Ping.
Can anyone tell me more about fw 1.75?

(In reply to Wolfgang Haupt from comment #26)
> Ping.
> Can anyone tell me more about fw 1.75?

Hi, 
We have got the official release of the FW, wait for a day or two it will be uploaded on downloadcenter

It's been a few days now.
In the downloadcenter 1.72 is still latest.

(In reply to Wolfgang Haupt from comment #28)
> It's been a few days now.
> In the downloadcenter 1.72 is still latest.

ODMs are engaged to update LSPCON firmware images for the NUC devises and devises are doing testing. Once its done, downloadcenter will be updated with FW 1.76