Screen flickers intermittently

[Dave Roberts]

Hardware is a Dell XPS13 9350 (2015 edition), firmware 1.0.4, with a 1920x1080 non-touchscreen display.

After installing beta1, I had a "screen flickering" issue. What I mean by that is that the screen goes off or completely black for a very short period - enough to notice it, but not enough to leave you with nothing - then it comes back and shows the DE. This may happen many times in succession with no set period, or it may happen once and be OK for 10 minutes. It's seemingly completely random.

With alpha1 and alpha2 there were no such issues on the same machine. Additionally, this appears to be an issue with Ubuntu Mate only. I subsequently tested and installed (vanilla) Ubuntu and Xubuntu and they are not affected by the same issue.

I don't even know where to start debugging this. I currently still have Xubuntu but am happy to re-install Ubuntu Mate (last night's daily also had the problem, having tested it from a LiveUSB).

[Martin Wimpress  (flexiondotorg)]

What graphics chipset does this machine have? Intel IGP, AMD Radeon, nVidia?

I ask because one of my computers has had the same issue since, I thought it was a hardware fault developing. My has Intel Corporation Broadwell-U Integrated Graphics. As you say intermittent. Please provide some more information about your machine.

[Martin Wimpress  (flexiondotorg)]

Please fully update your Ubuntu MATE 16.04 beta computer.

    sudo apt-get update
    sudo apt-get dist-upgrade

Then add my PPA for Ubuntu MATE Xenial which contains packages updated bug fix packages.

  * https://launchpad.net/~ubuntu-mate-dev/+archive/ubuntu/xenial-mate

    sudo apt-add-repository ppa:ubuntu-mate-dev/xenial-mate
    sudo apt-get update
    sudo apt-get dist-upgrade

Now restart, and let me know if the problem is resolved. Thanks.

[Martin Wimpress  (flexiondotorg)]

This morning the flickering is back. So my changes don't help. I did some searching, it seems we are not the only ones with this issue:

  * https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/1522922
  * http://ubuntuforums.org/showthread.php?t=2286157

[Dave Roberts (vpasvid)]

My graphics hardware:-
[code]
$ sudo lshw -c video
  *-display
       description: VGA compatible controller
       product: Sky Lake Integrated Graphics
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 07
       width: 64 bits
       clock: 33MHz
       capabilities: pciexpress msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915_bpo latency=0
       resources: irq:277 memory:db000000-dbffffff memory:90000000-9fffffff ioport:f000(size=64)
[/code]

Using your PPA and updating hasn't helped - that said, the flickering has not been so frequent, but it does still happen.

I looked at the video posted in comment 12 of the other ticket and the flickering there is different (though I accept that it could be the same issue). Also, if the issue were as old as that, wouldn't I have had the problem with the alpha installations that I did? Just a complete guess on my part, of course.

[Dave Roberts (vpasvid)]

Hopefully some useful information: I booted to Xubuntu to get a comparison of loaded driver and any errors in dmesg (none that I could see)..

xubuntu@xubuntu:~$ sudo lshw -C video
  *-display
       description: VGA compatible controller
       product: Sky Lake Integrated Graphics
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 07
       width: 64 bits
       clock: 33MHz
       capabilities: pciexpress msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915_bpo latency=0
       resources: irq:277 memory:db000000-dbffffff memory:90000000-9fffffff ioport:f000(size=64)
xubuntu@xubuntu:~$ dmesg | grep i915
[ 5.983866] [drm] Finished loading i915/skl_dmc_ver1.bin (v1.26)
[ 6.017521] [drm] Initialized i915_bpo 1.6.0 20160214 for 0000:00:02.0 on minor 0
[ 7.875826] i915_bpo 0000:00:02.0: fb0: inteldrmfb frame buffer device
[ 13.005842] snd_hda_intel 0000:00:1f.3: bound 0000:00:02.0 (ops i915_audio_component_bind_ops [i915_bpo])

I then rebooted to Mate to get a comparison from dmesg (having done the lshw previously). At this point I updated all packages, so I'm on the latest kernel build...

$ uname -a
Linux laptop 4.4.0-14-generic #30-Ubuntu SMP Tue Mar 15 13:04:17 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

At this time, I put the laptop on charge as the battery was getting low. Whilst doing other stuff at the same time, I noticed a lack of flickering. During the 2.5hr charge cycle, I didn't get a single instance of flickering!

Once fully charged, I disconnected from the mains and almost immediately the flickering started again. Here's what dmesg threw up...

$ dmesg | grep i915
[ 1.378125] [drm] Finished loading i915/skl_dmc_ver1.bin (v1.26)
[ 1.405100] [drm] Initialized i915_bpo 1.6.0 20160214 for 0000:00:02.0 on minor 0
[ 1.645331] i915_bpo 0000:00:02.0: fb0: inteldrmfb frame buffer device
[ 8.862716] snd_hda_intel 0000:00:1f.3: bound 0000:00:02.0 (ops i915_audio_component_bind_ops [i915_bpo])
[ 8923.607981] [drm:intel_cpu_fifo_underrun_irq_handler [i915_bpo]] *ERROR* CPU pipe A FIFO underrun

So: no problems in Ubuntu/Xubuntu. No problems in Ubuntu Mate when on a/c power. It only happens (so far) with Mate and running on battery.

[Jeremy LaCroix (j-jlacroix)]

Same problem here. I'm also not convinced that this is a duplicate of that bug. I saw a video posted there, and my issue does not look like that. I do not have this issue while charging, only while on battery. I can fix this problem by installing the following three kernel deb files:

http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.4-wily/linux-headers-4.4.0-040400-generic_4.4.0-040400.201601101930_amd64.deb

http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.4-wily/linux-headers-4.4.0-040400_4.4.0-040400.201601101930_all.deb

http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.4-wily/linux-image-4.4.0-040400-generic_4.4.0-040400.201601101930_amd64.deb

After installing those debs and running that kernel, there's no issue whatsoever. With Xenial out soon, can we increase the priority on this bug?

[Dave Roberts (vpasvid)]

Confirmed: I've installed that kernel build and I've not seen a single instance of the screen blanking out. (It also fixed the wifi, which broke with this week's updates, but that's another issue.) So thank you!

Right... the so-called duplicate bug ends up referencing a specific commit which appeared to cause their issue. If that commit is still in the source for this 4.4.0 build, then we don't have a duplicate. I just don't know how to check that.

It's also not been answered as to why this only affects the Mate DE.

[Jeremy LaCroix (j-jlacroix)]

I'm glad that the kernels I linked to fixed it for you. I removed the duplicate status. I see no evidence that this has anything to do with the other bug, and the video I saw in the other bug does not look like this issue.

I think the kernel team needs to seriously look at this bug, my theory is that it only affects Skylake hardware, and there are A LOT of Skylake machines being sold today.

[Martin Wimpress  (flexiondotorg)]

My hardware that is affected by this issue is not Skylake.

[Jeremy LaCroix (j-jlacroix)]

Does this go away if you try disabling tlp.service? A user named Dio M mentioned on the Ubuntu MATE G+ page that disabling that made the flicker go away. I've not had a chance to try this myself but I will try it late this evening.

[Zachary Larsen (chiefmanyrabbitguteat)]

I think I am also affected by this bug. Will install kernels above from Wily, to see if that fixes it. Mine flickers intermittently, but can be provoked by moving the mouse cursor from one display to the other and back.

[Zachary Larsen (chiefmanyrabbitguteat)]

Me again... Don't know if I have the same bug as you all, but updating to Kernel 4.5.1 fixed the issue for me.

[Jeremy LaCroix (j-jlacroix)]

I did have a chance to disable tlp.service, and it fixed the issue for me. It's been a few days now with no flickering at all. I still think this is a kernel issue, since I can also fix this by side-loading an unsupported kernel without disabling tlp.service and the issue will also be fixed. I'm not sure yet what it means in regards to the fact that disabling tlp.service fixes the issue.

I really think there are two unrelated flicking issues here, as users of Ubuntu vanilla have the issue as well but their flicker issue looks different than the one I experience.

[Dave Roberts (vpasvid)]

I have installed the proper 16.04 LTS release with the 4.4.0-21 kernel and still have the screen blanking issue. It's no better or worse than the beta releases, except that I did occasionally get it when charging the battery - something that I'd not previously experienced.

Installing 4.5.2 kernel did not fix the issue for me, unfortunately.

The only one that works is the 4.4.0-040400 build.

I've no idea if tlp is running on my system. There's nothing in the process list, but if it's not got "tlp" in the process name, then I'm not going to find it.

Zachary Larsen - I have no external monitor to provoke the issue, it just happens anyway.

[Jeremy LaCroix (j-jlacroix)]

Why was this bug marked a duplicate of 1554613 again? I don't see how they could be the same. This bug affects only MATE. The other one affects other desktop environments and the symptoms look completely different. On my end, I've switched away from MATE and life is good now, no more flickers.

[Dave Roberts (vpasvid)]

Having read through 1554613, there are a lot of similarities (unlike with 1522922 that this was previously marked a duplicate of) and I can't immediately think of a reason to say it's not a duplicate. Except to repeat the fact that I only get this problem when running with Ubuntu Mate.

Right now, I'm running with (Unity) Ubuntu...
$ sudo lshw -c video
  *-display
       description: VGA compatible controller
       product: Sky Lake Integrated Graphics
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 07
       width: 64 bits
       clock: 33MHz
       capabilities: pciexpress msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915_bpo latency=0
       resources: irq:277 memory:db000000-dbffffff memory:90000000-9fffffff ioport:f000(size=64)
$ uname -a
Linux laptop 4.4.0-21-generic #37-Ubuntu SMP Mon Apr 18 18:33:37 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux

As you can see, same hardware, same driver, current kernel. I've not had a single instance of the screen blanking out since installing it last weekend. Before that, using Mate and the same kernel, it would happen as previously described.

[Jeremy LaCroix (j-jlacroix)]

I've seen video on Youtube of the other bug, it looks like nothing I've experienced. It's completely different. I think the MATE team need to look at this and tell us why it only happens with MATE and not with any other DE.

Assigning this bug as a duplicate of the other runs the risk of halting progress. While this is listed as a duplicate, the proper channels won't be looking at it because they'll be under the false impression that they're the same. I don't think it's appropriate to mark a bug as a duplicate unless that's been proven. Although I could be wrong, I've made a strong case on why these bugs are NOT the same.

[Jeremy LaCroix (j-jlacroix)]

I still haven't been able to reproduce this bug on a desktop environment other than MATE. Has a bug been filed against the MATE desktop environment? This bug has caused me to remove Ubuntu MATE from my laptop, and go with the GNOME edition. With Ubuntu GNOME, everything has been 100% problem free.

I think this bug being marked as a duplicate of #1554613 needs to be seriously re-evaluated. No matter how hard I try, I cannot reproduce this anywhere other than with MATE. That bug is affecting other flavors of Ubuntu as well. I'd really like to see this bug fixed and do whatever I can to help, but if we're jumping to conclusions that it's a duplicate of an unrelated bug, we're helping no one.

[Martin Wimpress  (flexiondotorg)]

Ubuntu MATE is the only flavour that pre-installs TLP. On some Intel IGPs TLP can cause the flickering occur, without TLP the flickering is not present. But TLP is not the cause it is simply the catalyst for an underlying kernel issue. Many Intel IGPs are affected without the presence of TLP, not just Skylake.

It is TLP that differentiates Ubuntu MATE from the other flavours. MATE is not the cause, passing kernel debug option can prove this. I am now running mainline Kernel 4.6 and TLP and flickering is gone. If you have a system that exhibits flickering please install the kernel below as a workaround:

  * http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.6-yakkety/

[Jeremy LaCroix (j-jlacroix)]

@Martin, I think you may be misunderstanding or maybe I forgot to mention that TLP wasn't the culprit for me after all. At one time I thought that TLP was the culprit. I disabled it, and I *thought* that TLP was causing it. I can reproduce the flickers on Ubuntu MATE with or without TLP enabled. I was wrong, it had nothing to do with TLP.

The flickers only happen for me on Ubuntu MATE. This has nothing to do with TLP.

[Martin Wimpress  (flexiondotorg)]

TLP has been proven to exacerbate this issue by several people in the Ubuntu MATE community. In post #6 you stated the issue was resolved by using an alternative kernel, the issue reporter stated the same in post #7.

If you can spare the time please install Ubuntu MATE on an external USB 3.0 disk or spare hard disk and install kernel 4.6 and report back :-)

[Jeremy LaCroix (j-jlacroix)]

The issue did seem to go away when I disabled TLP, but after a week, the issue came back with a vengeance. So for me, disabling TLP only helped temporarily.

I am more than happy to wipe my laptop and reinstall Ubuntu MATE to help diagnose this bug. I should be able to do so at some point during this week. I'll test it for a week or so and see what happens.

As for the kernel, yes, the issue did get resolved using an alternative kernel. However, my main interest is to help get this issue fixed for Ubuntu MATE's stock kernel, because more people will benefit if this is fixed legitimately rather than having everyone install an unsupported kernel. I can install 4.6 and test it, but I would hope this gets fixed in a point release of the 16.04 kernel.

I'll let you know what I find when I reimage my laptop.

Thanks!

[Jeremy LaCroix (j-jlacroix)]

In my testing so far, I've reimaged my laptop with Ubuntu MATE, disabled and stopped tlp.service, and I still have the flickers.

[Dave Roberts (vpasvid)]

@Martin thanks for the information about what differentiates Ubuntu Mate. With that in mind I booted my laptop using the Mate release on a live USB. Immediately there is flickering but when I disabled TLP the flickering stopped and I've not seen it for over an hour.

It's difficult to say if this is actually a duplicate of #1554613 and it's a pity that Jeremy is experiencing different issues, but it's certainly worked for my machine. Shame I didn't know before I jumped DE.

[Jeremy LaCroix (j-jlacroix)]

I want to reiterate, disabling TLP did fix it for me for a while, but the problem ended up coming back after a week. I'm having this problem now even with TLP disabled. I also have Virtualbox installed (with no VMs running) and all of the latest updates. Not sure if any of that matters.

So far, no flickers on the 4.6 kernel though.

As for this bug being a duplicate of #1554613, it's clearly not. It may have the same root trigger (something in the kernel) but this bug affects only MATE, while #1554613 seems to affect other flavors. There's no way they can be the same, especially since I'm able to reproduce this bug with or without TLP.