Created attachment 188351 [details] Dmesg and lspci A display connected via a thunderbolt was working with kernel 3.17 but is not detected with kernel 4.1 The issue is also documented here -> https://bugzilla.redhat.com/show_bug.cgi?id=1260796 Attaching logs (dmesg and lspci in the same file)
Created attachment 188411 [details] Dmesg with 3.18.20 Good dmesg (Second monitor works)
Please send to the graphics/video driver people, this is not a "hotplug" issue.
Well, I think it's the thunderbolt module. There is no such component in bugzilla.
Nothing obvious that's wrong in dmesg, please add drm.debug=14 module parameter and attach the dmesg. A bisect result would be great.
Created attachment 188931 [details] 3.18.20 - good with drm.debug=14
Created attachment 188941 [details] 4.1.6 - doesn't work with drm.debug=14
I can bisect this weekend (and hack a rough patch probably) if this is not enough.
Please try v4.3-rc, I think this may be fixed upstream.
Yes, I confirm 4.3-rc3 fixes this issue.
(In reply to Radu Andries from comment #9) > Yes, I confirm 4.3-rc3 fixes this issue. Thanks for testing, closing. There are *many* commits which may have alone, or in some combination, fixed the issue. Some of them may not even be suitable for backporting to stable kernels. Since it's fixed upstream, I'm afraid we're not putting in the effort to identify the commits that fixed the issue. However, if it's of value to you to have the fixes backported, you should do a reverse git bisect and find out, and then let us know. Alternatively try backporting the commits referencing i2c or aux in drivers/gpu/drm/drm_dp_helpers.c and drivers/gpu/drm/i915/intel_dp.c, I'm fairly sure that's where the fix is. Thanks.