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Problem

When attempting to set the resolution of my 4K external display to 3840x2160, the external display loses signal and moments later the entire system hangs.

The display is connected to my XPS 13 9350 Developer Edition running Ubuntu 16.04 using a USB-C to DisplayPort adapter.

Hardware:

Attempted Fixes

Setting Resolution Manually

I have tried using xrandr to manually set the mode and refresh rate of the display. Setting it to 4K at 60Hz shows the same problems as setting it in the GUI but if I set it to 4K at 30Hz it works fine.

Doesn't work: xrandr --output DP1 --mode 3840x2160 -r 60.00
Does work : xrandr --output DP1 --mode 3840x2160 -r 29.98

Multiple Adapters

I have attempted using multiple different USB-C to DisplayPort adapters, both of which give the impression that they are capable of 4K resolution at 60Hz. The adapter used does not appear to make a difference to the problem.

Kernel Update

I have updated the kernel to version 4.6 in case better support was added for the integrated Iris graphics. This does not appear to have made any difference.

I hope the steps I have taken that are documented above will help to diagnose the problem.

Amias
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andy1633
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  • Having the same issue with the XPS 9350 and monitor Dell P2415Q (using the Plugable USB-C to DisplayPort Adapter Cable https://www.amazon.com/Plugable-DisplayPort-Chromebook-ThunderboltTM-3840x2160/dp/B01EXKDRAC/ref=sr_1_2?ie=UTF8&qid=1469101485&sr=8-2&keywords=pluggable+usb-c+dp). Upgrading the kernel to 4.6.4 or 4.7.0rc7 does not seem to solve the problem. At least after the BIOS update to 1.4.4 I was able to use it with the refresh rate of 29.98 (before it would crash the OS). – aramboi Jul 21 '16 at 11:45
  • The usb c port is the weakest link here, I have a near identical setup on my m3800 but the display port is over thunderbolt and it works fine. One thing to check is that the monitor is in display port 1.2 mode or better. You could also try reducing the refresh by 1hz to 59khz to make it easier on the computer. You can generate modelines with CVT and apply them with xrandr Are there any specific error messages ? – Amias Jun 02 '16 at 12:30
  • The monitor is set to DisplayPort 1.2 mode according to instructions in the manual. The only actual error message I have seen is an error saying it couldn't load the display configuration file after a reboot. I will have a look at adjusting the refresh rate like you suggested. – andy1633 Jun 02 '16 at 12:57
  • i've seen that error before, its because the monitor didn't respond quickly enough, it takes several seconds to sync a 4k monitor. – Amias Jun 02 '16 at 14:29
  • this thread has lots of suggestions http://ubuntuforums.org/showthread.php?t=2301071&page=35 – Amias Jun 02 '16 at 14:38
  • I can confirm exactly the same problem with the Lenovo Yoga 900 using USB-C to HDMI and DisplayPort adapters. The display is blank at 60Hz even though xrandr reports the mode is available. Reducing frequency slightly also does not work - but going down to 30Hz does work - however the latency is then horrible. I have eliminated my hardware as the problem, since booting to Windows 10 with the same adapters/display gives me rock solid 3840x2160 at 60Hz through USB-C to both HDMI and DisplayPort. – drplix Jul 16 '16 at 09:00
  • Should also mention that I am running stock Ubuntu 16.04 on the 4.4 kernel I too have tried the 4.5 and 4.6 kernels but with no improvement. – drplix Jul 16 '16 at 09:02
  • Does your machine also have the Intel Iris 540 graphics chipset? – andy1633 Jul 16 '16 at 10:21
  • Its latest generation Intel Skylake - I think its Iris 520. Here's the lshw details... 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 – drplix Jul 16 '16 at 15:27
  • Yes here's what "About This Computer" shows: Intel® HD Graphics 520 (Skylake GT2) – drplix Jul 16 '16 at 15:32
  • One more tip I just discovered. After switching to 4K at 30Hz I had terrible latency - window drag not keeping up with mouse. Keypress feeling laggy when typing etc. I discovered that if I reset unity with "unity --replace" the responsiveness is a lot better - but still nothing like Windows 10 with 4K at 60Hz. – drplix Jul 16 '16 at 15:53
  • Please do not post "this affects me" or "I can confirm this" as an answer. When you all have sufficient reputation, you will be able to comment on posts. – Thomas Ward Aug 22 '16 at 22:39
  • That's good news that 4.8+ seems to start solving this issue, I've had my P2715Q since 2015 and can't get it to work in a stable way on 16.04 on the XPS13 above 1080p@60. You're testing from this PPA? http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.8/ – Alex Oct 05 '16 at 17:24

1 Answers1

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Having the same issue with the XPS 9350 (QHD+, BIOS v1.4.4) and external monitor Dell P2415Q. I am using the Plugable USB-C to DisplayPort Adapter Cable.

Upgrading the kernel to v4.8-rc2 seems to solve this problem. I am writing this post on the external monitor running at 3840x2160 60Hz.

Having said that, it is pretty unstable. It crashes often when connecting/disconnecting the adapter and there are some graphical artefacts that appear when moving the mouse and windows around.

My hope is that the final version of the kernel will iron out these issues or at least kernel 4.9 will.

UPDATE: Ubuntu (Gnome) 16.10 works great for the configuration above. No issues so far, except some monitor flickering from time to time.

aramboi
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    Looks like Intel have provided some updated drivers in the 4.8 kernel. http://www.phoronix.com/scan.php?page=news_item&px=Intel-DRM-Next-Linux-4.8 – andy1633 Aug 23 '16 at 08:05
  • According to this https://news.slashdot.org/story/16/06/09/1433229/ubuntu-1610-to-be-powered-by-linux-kernel-48, Ubuntu 16.10 will ship with kernel 4.8 so hopefully all these problems will go away in October. – aramboi Aug 25 '16 at 11:28
  • I have exactly the same hardware as you (except for the monitor - mine's a P2715Q). With the 4.4 kernel, Ubuntu 16.04 just crashed when plugging in the USBC to DP adapter. I updated to kernel 4.7 and the adapter is usable up to 2560x1440 @ 60Hz, but still crashes with 4k. – Leo Brito Sep 08 '16 at 17:09
  • @brito at the moment it seems only kernel 4.8 will solve these issues. I am using 4.8-rc7 now and it seems fairly stable. If you don't want to update you kernel to an RC, you can wait for a month till the Ubuntu 16.10 release which would come with this version (hoping it reaches stable by then). – aramboi Sep 19 '16 at 11:59
  • @aramboi 4.8 is out and I just installed it fine on Ubuntu 16.04. It solves the 4k@60Hz via USBC-DP issue, _but_ now wifi is terrible with intermittent `brcmfmac` errors. Did you experience any such errors? I'll open a question about this anyway. – Leo Brito Oct 04 '16 at 14:00
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    @brito I have the developer edition of the XPS which comes with the intel wifi chip, not the broadcom one. For me it works fine with the 4.8 kernel stable (I have issues with the wired connection though). – aramboi Oct 05 '16 at 12:29