[Bug 101205] New: [i915][BYT] Blank screen on MIPI panel

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=101205

            Bug ID: 101205
           Summary: [i915][BYT] Blank screen on MIPI panel
           Product: DRI
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: dimitry at cos.flag.org
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 131526
  --> https://bugs.freedesktop.org/attachment.cgi?id=131526&action=edit
Syslog for the faulty Pipo X8 (Z3735F) unit

I have two very similar Baytrail devices: Pipo X8 and Pipo X8S.

The former (X8) is based on Z3736F and runs fine. The latter (X8S) is based on
Z3735F and gets a blank screen once the i915 driver is loaded.

Both units run identical set up software-wise:

distro: Gentoo
kernel: drm-tip branch (713f8e of 16 May)
xorg: 1.19.2
xf86-video-intel: 2.99.917_p20170216

Comparing the logs I can see the faulty unit seems to be missing some MIPI
initialization commands. Here is the diff of the logs between the good unit
(left) and the faulty one (right):

https://www.diffchecker.com/tv4c7jTl

The HDMI output on the faulty unit works fine. Attached are the logs for both
the good and the faulty units with drm.debug=0x1e

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