Intel Skylake video: no output on VGA port

Bug #1619677 reported by Owen Dunn on 2016-09-02
18
This bug affects 3 people
Affects Status Importance Assigned to Milestone
linux-lts-xenial (Ubuntu)
Undecided
Unassigned

Bug Description

Ubuntu release: 14.04.5 LTS
Kernel: linux-image-4.4.0-36-generic 4.4.0-36.55~14.04.1

I have a Dell Optiplex 7040 with an Intel Sky Lake r6 video card:

00:02.0 VGA compatible controller [0300]: Intel Corporation Sky Lake Integrated Graphics [8086:1912] (rev 06) (prog-if 00 [VGA controller])
        Subsystem: Dell Device [1028:06b9]
        Flags: bus master, fast devsel, latency 0, IRQ 128
        Memory at f6000000 (64-bit, non-prefetchable) [size=16M]
        Memory at e0000000 (64-bit, prefetchable) [size=256M]
        I/O ports at f000 [size=64]
        Expansion ROM at <unassigned> [disabled]
        Capabilities: <access denied>
        Kernel driver in use: i915_bpo

Running trusty with the lts-xenial kernel, I get no output on the built-in VGA port after grub has started the kernel. The monitor goes into power-save mode. The system does boot correctly and I can ssh into it. If I connect the monitor using one of the other ports (HDMI or DisplayPort) everything is visible.

When only the VGA port is connected to the monitor the kernel dmesg output contains:

[ 3.613697] i915_bpo 0000:00:02.0: DP-3: EDID block 0 invalid.
[ 3.614522] i915_bpo 0000:00:02.0: No connectors reported connected with modes

Owen Dunn (osd1000) wrote :

The problem only manifests itself when the monitor is attached through a KVM switcher.

Launchpad Janitor (janitor) wrote :

Status changed to 'Confirmed' because the bug affects multiple users.

Changed in linux-lts-xenial (Ubuntu):
status: New → Confirmed
Ruslan (b7-10110111) wrote :

This also happens to me with

00:02.0 VGA compatible controller: Intel Corporation Sky Lake Integrated Graphics (rev 06)

It happened after upgrade from linux 4.4.0-31-generic to 4.4.0-36-generic. Previously it worked flawlessly, and it's my current workaround to boot with this older kernel.

I'm attaching the Xorg log from bad session. Note the line there:

[ 9.898] (WW) intel(0): No outputs definitely connected, trying again...

It's likely related.

Ruslan (b7-10110111) wrote :

Here's the good session log for comparison.

Ruslan (b7-10110111) on 2016-09-04
tags: added: regression-update
Ruslan (b7-10110111) on 2016-09-04
summary: - Optiplex 7040 - No output on VGA port
+ Intel Skylake video: no output on VGA port
Philipp Wendler (philw85) wrote :

We are also experiencing such problems on a range of different notebooks with an Intel HD Graphics 520 (Skylake generation). We tested multiple Fujitsu Lifebook E746 with their onboard VGA connector and a ThinkPad T460s with different adapters from DisplayPort, under both Ubuntu 16.04 with kernel 4.4 and Ubuntu 16.10 with kernel 4.8.

In a few cases (certain combinations of notebooks and projectors) we got a working VGA connection, bust mostly not. If a connection could be established, it was stable.

It seems that VGA ports on Linux with Skylake GPUs are completely unreliable.

According to http://www.anandtech.com/show/9483/intel-skylake-review-6700k-6600k-ddr4-ddr3-ipc-6th-generation/4, Skylake has no internal VGA port anymore and all VGA connectors are build using adapters, which could explain this (worse timings and signal quality for example).

However, Windows 10 on the same notebooks never had a problem with VGA output in our tests, so it seems that there is still some influence of the OS.

This is a major problem for our users because they absolutely rely on a working VGA connector, because when giving talks (for example on academic conferences) it is still the norm that only a VGA connection to the projector is available.

Gwendal (gwendal) wrote :

Possibly related bug? https://bugs.freedesktop.org/show_bug.cgi?id=97558

Fedora user here, I think that I have a similar problem: beamers were working perfectly fine until a system update weeks ago.

My configuration:
- Fedora 25 beta (but the problem was there with F24 as well)
- Intel(R) Core(TM) i5-4210U CPU @ 1.70GHz
- 00:02.0 VGA compatible controller: Intel Corporation Haswell-ULT Integrated Graphics Controller (rev 0b)
- linux 4.8.4-301.fc25.x86_64

Regular Iijama monitors work fine in VGA (both the one I have at home and the one from my office, which is a Prolite XB2485WSU).

However beamers (rather old, which is typical in universities) do not work in VGA: nothing detected with xrandr or anything else. I have this situation with two different beamers.

If I can provide more information, please do not hesitate to ask!

Thanks!

Gwendal (gwendal) wrote :

OK, I've just tested on the same system with an older kernel 4.6.0, and it works again using VGA on the same old beamer that didn't work in 4.8.4.

On Fedora 25 beta I used koji to install 4.6:

$ wget https://kojipkgs.fedoraproject.org//packages/kernel/4.6.0/1.fc25/x86_64/kernel-4.6.0-1.fc25.x86_64.rpm https://kojipkgs.fedoraproject.org//packages/kernel/4.6.0/1.fc25/x86_64/kernel-core-4.6.0-1.fc25.x86_64.rpm https://kojipkgs.fedoraproject.org//packages/kernel/4.6.0/1.fc25/x86_64/kernel-modules-4.6.0-1.fc25.x86_64.rpm
$ sudo rpm -ivh --oldpackage ./kernel-4.6.0-1.fc25.x86_64.rpm ./kernel-core-4.6.0-1.fc25.x86_64.rpm ./kernel-modules-4.6.0-1.fc25.x86_64.rpm

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