Bug 97558

(In reply to Andreas Kloeckner from comment #0)
> More detailed info:
> https://gist.github.com/inducer/12d4507f454c27319e5585629d9727a5

Please keep all information in the bug.

Created attachment 126157 [details]
Debian package info (versions etc)

Uploaded Debian bug info from gist as attachment.

I should add that this happened not just with the projection system at the University of Illinois (my employer), but also at a conference at the University of Warwick in the UK this summer.

Can you attach full dmesg from the working and non-working setups, both with drm.debug=0xe passed to the kernel command line on boot.

Created attachment 126447 [details]
Dmesg log with drm.debug=0xe on 4.6

Created attachment 126448 [details]
Dmesg log with drm.debug=0xe on 4.8

Logs uploaded. The plug attempts are towards the end of the logs.

That kernel 4.8 is Debian's 4.8rc5, if it makes a difference.

Please test
git://github.com/vsyrjala/linux.git dp_connection_unknown

Thank you for looking into this!

I tried, but it turns out the only plausible way for me to build a kernel usable with my distribution (Debian) is as a patched distro kernel. I tried turning your patch into something I can apply on top of 4.8-rc5 (the current distro kernel), but I failed. Just using your two most recent commits don't apply cleanly, and the complete diff between 4.8-rc5 and your kernel doesn't apply cleanly to the distro kernel because of conflicts with distro patches. Any advice? Is there some way for you to extract only the i915-related changes? Thanks, and sorry for not responding sooner.

(In reply to Andreas Kloeckner from comment #11)
> Thank you for looking into this!
> 
> I tried, but it turns out the only plausible way for me to build a kernel
> usable with my distribution (Debian) is as a patched distro kernel.

I don't know what kind of crazy setup you have, but Debian itself definitely does not require any out of tree patches in the kernel.

I can confirm that adding the last 2 commits from the branch you listed on top of todays drm-intel-nightly solves the problem! When masking pin 15 of VGA (EDID i2c clock I think) I can still get up to 1024x768 detected with the commits, while the display is not detected at all without the commits. Unfortunately, many projectors still do not provide the i2c interface or the cables that are used simply do not provide all the pins.

Will these commits be merged to intel-drm-nightly?

Hello,

I have the same problem (I think): 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)
- 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! Regards

(In reply to Gwendal from comment #15)
> Hello,
> 
> I have the same problem (I think): 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)
> - 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! Regards

I forgot to mention my CPU name:

- Intel(R) Core(TM) i5-4210U CPU @ 1.70GHz

Also, a recent possibly related bug: https://bugs.launchpad.net/ubuntu/+source/linux-lts-xenial/+bug/1619677

commit 16c83fad79ca912b8b5bbdcb5272794a2be41262
Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
Date:   Mon Oct 3 10:55:16 2016 +0300

    drm/i915: Allow DP to work w/o EDID

(In reply to Gwendal from comment #16)
> (In reply to Gwendal from comment #15)
> > Hello,
> > 
> > I have the same problem (I think): 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)
> > - 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! Regards
> 
> I forgot to mention my CPU name:
> 
> - Intel(R) Core(TM) i5-4210U CPU @ 1.70GHz
> 
> Also, a recent possibly related bug:
> https://bugs.launchpad.net/ubuntu/+source/linux-lts-xenial/+bug/1619677

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