[Bug 219128] Mini-DP to VGA adapter doesn't work on FreeBSD 11.0-R

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=219128

            Bug ID: 219128
           Summary: Mini-DP to VGA adapter doesn't work on FreeBSD 11.0-R
           Product: Base System
           Version: 11.0-RELEASE
          Hardware: amd64
                OS: Any
            Status: New
          Severity: Affects Some People
          Priority: ---
         Component: kern
          Assignee: freebsd-bugs at FreeBSD.org
          Reporter: naito.yuichiro at gmail.com

Created attachment 182379
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=182379&action=edit
dmesg.log

I'm using Macbook Air 2012 for FreeBSD-11.0R.

I found my Mini-DisplayPort to VGA adapter doesn't work
to add second display for my presentation.

I don't think my adapter is broken,
because I rebooted my Macbook Air with OS X, it works.
And I remember my adapter worked on FreeBSD-10.3R.

On my FreeBSD-11.0R,
I've seen following dmesg, since I attached the adapter.

```
$ dmesg | tail -5
error: [drm:pid0:intel_dp_i2c_aux_ch] *ERROR* too many retries, giving up
error: [drm:pid0:intel_dp_i2c_aux_ch] *ERROR* too many retries, giving up
error: [drm:pid0:intel_dp_i2c_aux_ch] *ERROR* too many retries, giving up
error: [drm:pid0:intel_dp_i2c_aux_ch] *ERROR* too many retries, giving up
error: [drm:pid0:intel_dp_i2c_aux_ch] *ERROR* too many retries, giving up

$ uname -a
FreeBSD air 11.0-RELEASE-p9 FreeBSD 11.0-RELEASE-p9 #0: Tue Apr 11 08:48:40 UTC
2017     root at amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC  amd64

```

According to `https://wiki.freebsd.org/Intel_GPU`,
I got debug messages with `sysctl hw.dri.debug=2`.
See the attached `dmesg.log` file.

For my hardware information,
I attach `devinfo.log` and `pciconf.log`.

For software information,
I attach `kldstat.log`, `pkginfo.log` and `Xorg.0.log`.

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