[Bug 93845] New: i915 vlv blank screen after drm initialisation (4.4.0 mainline & drm-intel-nightly)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=93845

            Bug ID: 93845
           Summary: i915 vlv blank screen after drm initialisation (4.4.0
                    mainline & drm-intel-nightly)
           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: greg at gothack.ninja
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 121255
  --> https://bugs.freedesktop.org/attachment.cgi?id=121255&action=edit
dmesg

Attempting to get linux booting on a Vulcan Excursion XB, having issues with
i915 (nomodeset / efi graphics work okay).

Black screen - with backlight - after i915 is initialised, I've made some dumps
of dmesg, etc. everything looks okay besides a backtrace for a suspicious
warning:
[   11.122021] WARNING: CPU: 2 PID: 161 at drivers/gpu/drm/drm_irq.c:1271
drm_wait_one_vblank+0x1c4/0x1d0 [drm]()
[   11.122022] vblank wait timed out on crtc 0

Also note the backlight control also seems like it could be busted:
[    8.151269] [drm:pwm_setup_backlight [i915]] *ERROR* Failed to own the pwm
chip
[    8.151287] [drm:intel_panel_setup_backlight] failed to setup backlight for
connector DSI-1

I also had issues dumping the vbios, no amount of prodding gave me a successful
dump (echo 1 > rom; cat rom; echo 0 > rom, nor intel_bios_dumper [the latter of
which gives me "Couldn't read graphics card ROM: Input/output error" - I'll try
looking at an strace]). Any suggestions there would be appreciated.

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