[Bug 107446] New: Monitor on 2nd DisplayPort is not initialized

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=107446

            Bug ID: 107446
           Summary: Monitor on 2nd DisplayPort is not initialized
           Product: DRI
           Version: unspecified
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: glogow at fbihome.de
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

I'm on Ubuntu 18.04.

While analyzing bug 107441 I found that kernels since 4.17 failed to initialize
the 2nd monitor attached to my Skylake HW, an Acer n4640g (Celeron® G3900T").

The most obvious missing lines from the DRM debug diff is the missing
retraining like:

[drm:intel_dp_check_link_status [i915]] DDI D: channel EQ not ok, retraining
...

and then there is the missing drm_atomic_add_affected_connectors:

 [drm:intel_dump_pipe_config [i915]] planes on this crtc
 [drm:intel_dump_pipe_config [i915]] [PLANE:28:plane 1A] disabled, scaler_id =
-1
-[drm:intel_dump_pipe_config [i915]] [PLANE:31:plane 2A] disabled, scaler_id =
-1
-[drm:intel_dump_pipe_config [i915]] [PLANE:34:cursor A] disabled, scaler_id =
-1
-[drm:drm_atomic_add_affected_connectors [drm]] Adding all current connectors
for [CRTC:47:pipe B] to         (ptrval)
-[drm:intel_atomic_check [i915]] [CONNECTOR:61:DP-3] checking for sink bpp
constrains
+[drm:intel_dump_pipe_config [i915]] [PLANE:33:plane 2A] disabled, scaler_id =
-1
+[drm:intel_dump_pipe_config [i915]] [PLANE:38:cursor A] disabled, scaler_id =
-1
+[drm:intel_atomic_check [i915]] [CONNECTOR:72:DP-3] checking for sink bpp
constrains
 [drm:intel_atomic_check [i915]] clamping display bpp (was 36) to EDID reported
max of 24
 [drm:intel_dp_compute_config [i915]] DP link computation with max lane count 4
max bw 270000 pixel clock 148500KHz

No idea if it's related, but 4.17 is also the first kernel to spill some ACPI
error messages before the splash screen:

[    0.049039] ACPI Error: Result stack is empty! State=        (ptrval)
(20180313/dswstate-65)
[    0.049046] ACPI Error: AE_AML_NO_RETURN_VALUE, Missing or null operand
(20180313/dsutils-612)
[    0.049050] ACPI Error: AE_AML_NO_RETURN_VALUE, While creating Arg 0
(20180313/dsutils-727)

Tested kernels are:
* Ok - Ubuntu 18.04 + linux-image-4.15.0-29-generic (4.15.0-29.31)
* Ok - Ubuntu 18.04 + linux-image-4.16.18-041618-generic
(4.16.18-041618.201806252030)
* Fail - Ubuntu 18.04 + linux-image-4.17.11-041711-generic
(4.17.11-041711.201807280505)
* Fail - Ubuntu 18.04 + linux-image-4.18.0-041800rc7-generic
(4.18.0-041800rc7.201807292230)

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