[Bug 89573] New: [BYT] screen goes black and stays black with Linux 4.0-rc2 when X starts on Dell Venue 8 Pro 3845 baytrail tablet

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=89573

            Bug ID: 89573
           Summary: [BYT] screen goes black and stays black with Linux
                    4.0-rc2 when X starts on Dell Venue 8 Pro 3845
                    baytrail tablet
           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: rw at nelianur.org
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 114294
  --> https://bugs.freedesktop.org/attachment.cgi?id=114294&action=edit
kernel .config

I'm trying to get Linux to work on a Dell Venue 8 Pro 3845 tablet that comes
preinstalled with Windows 8.1. I'm running Debian Testing (Jessie) installed
via Steve McIntyre's 64-bit kernel on 32-bit UEFI Debian Installer images [1].
If I go through the EFI boot menu, the device boots normally until X is started
and the screen goes black, flashes briefly, and then stays black. If I prevent
the intel X.org driver from loading by adding "nomodeset" to the kernel command
line I can proceed to a working, albeit rather slow, Gnome session. This report
is about getting accelerated graphics to work as well.

I noticed a number of Baytrail-related commits have gone into the kernel since
3.16.x which Jessie ships, so I've tried with a custom (yet unpatched) 4.0-rc2
build (and an unmodified Jessie user space).

The firmware is up to date (A02) and I should note that this is apparently not
the same hardware as in earlier reports [2] which were for the model 3830 Venue
8 Pro.

I'm attaching the relevant configuration and log files. Xorg is started without
an xorg.conf. There are two sets of logs one without and one with
"drm.debug=0x06". The system crashed hard sometime after acquiring the first
set.

The Xorg log does not contain errors. The kernel reports a "vblank wait timed
out on crtc 0". One thing I noticed as somewhat odd is that xrandr lists the
internal display (which AFAIK is connected via DSI) as "UNKNOWN1" rather than
the "DSI1" which users of the 3830 model have reported but I don't know how
significant that is. The internal display is the only display. There are no
external connectors.

Let me know if I can provide any additional info or logs.

Regards,

Rene


[1] http://blog.einval.com/debian/CDs/Jessie-EFI_5.comments
[2] https://bugs.freedesktop.org/show_bug.cgi?id=82880

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