[Bug 105887] [GLK] no signal after switch resolution from 1080p at 23.98

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=105887

--- Comment #94 from Daniel Scheller <d.scheller.oss at gmail.com> ---
(In reply to Clinton Taylor from comment #89)

Hi Clint,

> > Sadly can't just edit the comment. For reference, the hardware IDs for the
> > GLK GPU on this board (lspci -vvn):
> > 
> > 00:02.0 0300: 8086:3184 (rev 03) (prog-if 00 [VGA controller])
> > 	Subsystem: 1849:2212
> > 
> > Again, unconditionally waiting 50ms at the end of
> > intel_ddi_disable_transcoder_func() works, so I suspect all GLK hardware
> > needs this, not only the NUCs.
> 
> Daniel,
>    Could you add the following to to intel_quirks[] in intel_display.c  
> 
>      { 0x3184, 0x1849, 0x2212, quirk_increase_ddi_disabled_time },

Done (could have tried that myself though already since it's obvious it won't
do anything without matching hardware IDs). With that, your patch works well,
just like with the 50ms unconditional delay. My i915.ko now carries [1] (your
original patch plus unrelated fixups for the 4.15 backport) and [2] (with
additional hardware IDs), please ignore any debian changelog changes.

> I really don't want to add the delay to all GLK's, but even the ASrock
> photo's show the ITE chip in use on the board. I don't have a guaranteed way
> to detect the ITE chip on the boards.

The list of hardware IDs might get long though. On another forum, one user has
the same HDMI issue with an ASRock J4105-ITX with the "slower" (compared to
J5005) GLK iGPU, that one identifies with

  00:02.0 0300: 8086:3185 (rev 03) (prog-if 00 [VGA controller])
          Subsystem: 1849:2212

So, same subsys vendor+id, but different PCI ID. Thats why I added more IDs in
[2], the two mentioned by fatez and user.forums at gmail.com are in there aswell.

For anyone who wants to test: Ubuntu Kernel debs at [3].

[1]
https://github.com/herrnst/ubuntu-bionic-kernel/commit/92f7740df31c5c920d217db210594b4cd9e45413
[2]
https://github.com/herrnst/ubuntu-bionic-kernel/commit/b8c66deb38c5b8020b50bfb44c71e06a0275bba3
[3]
https://github.com/herrnst/ubuntu-bionic-kernel/tree/4.15.0-23.25-glktesting3-deb

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