[Bug 110030] regression bisected black screen with cursor

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=110030

--- Comment #4 from Manuel Mommertz <2kmm at gmx.de> ---
Created attachment 143674
  --> https://bugs.freedesktop.org/attachment.cgi?id=143674&action=edit
test-patch

I try to understand what exactly changed here so I looked into the sources. I
have found that the association between connectors and crtcs changes due to the
patch mentioned above. With the attached test-patch X works again and the
debugging output shows the exchange of crtc-pointers between the connectors:

[    2.878198] [drm:drm_setup_crtcs [drm_kms_helper]] NOT WORKING: CONN 4 -
crtc: ffffa36ef4054f48
[    2.878201] [drm:drm_setup_crtcs [drm_kms_helper]] NOT WORKING: CONN 5 -
crtc: ffffa36ef4054f00
[    2.878205] [drm:drm_setup_crtcs [drm_kms_helper]] WORKING:     CONN 4 -
crtc: ffffa36ef4054f00
[    2.878207] [drm:drm_setup_crtcs [drm_kms_helper]] WORKING:     CONN 5 -
crtc: ffffa36ef4054f48

In the duplicate bug you said:
> Not a bug in the kernel, xorg's modesetting driver needs to set all
> connectors/crtc's directly when using atomic. The legacy path disabled crtc
> B for you if you stole all its connectors for a different crtc. In the
> atomic case you need to disable it yourself.
> 
> This is a bug in x.org's modesetting driver.

Though it seems to me this is not related here as there are no stolen
connectors involved. And the source of the modesetting-driver from xorg already
has a part that disables crtcs without connection (see
https://cgit.freedesktop.org/xorg/xserver/tree/hw/xfree86/drivers/modesetting/drmmode_display.c
line 778)

So do you say the right path from here is to let the modesetting driver change
the association between the connectors and crtcs?

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