[Bug 75385] Dell Latitude E5440 screen goes blank when external VGA monitor connected

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=75385

--- Comment #24 from Daniel Vetter <daniel at ffwll.ch> ---
The logs look pretty sane and not really out of the ordinary. Normal detect
plus then a modeset, all not taking unduly long. But this here in the last file
doesn't look good:

[  841.799204] INFO: task kworker/0:0:4 blocked for more than 120 seconds.
[  841.799215]       Not tainted 3.12.13-desktop-2.mga4 #1
[  841.799219] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this
message.
[  841.799224] kworker/0:0     D ffff88011ea13e40     0     4      2 0x00000000
[  841.799320] Workqueue: events ironlake_panel_vdd_work [i915]
[  841.799326]  ffff880119b2bd80 0000000000000046 ffff880119b2bfd8
0000000000013e40
[  841.799335]  ffff880119b2bfd8 0000000000013e40 ffff880119b0c500
ffff880118c8db30
[  841.799344]  ffff880118c8db34 ffff880119b0c500 00000000ffffffff
ffff880118c8db38
[  841.799353] Call Trace:
[  841.799371]  [<ffffffff81614e39>] schedule_preempt_disabled+0x29/0x70
[  841.799381]  [<ffffffff81612f62>] __mutex_lock_slowpath+0x132/0x1b0
[  841.799391]  [<ffffffff81612fff>] mutex_lock+0x1f/0x30
[  841.799444]  [<ffffffffa00c81b5>] ironlake_panel_vdd_work+0x25/0x40 [i915]
[  841.799455]  [<ffffffff8107b15c>] process_one_work+0x17c/0x410
[  841.799463]  [<ffffffff8107bd41>] worker_thread+0x121/0x3b0
[  841.799472]  [<ffffffff8107bc20>] ? rescuer_thread+0x320/0x320
[  841.799481]  [<ffffffff81082750>] kthread+0xc0/0xd0
[  841.799489]  [<ffffffff81082690>] ? kthread_create_on_node+0x120/0x120
[  841.799500]  [<ffffffff8161e70c>] ret_from_fork+0x7c/0xb0
[  841.799508]  [<ffffffff81082690>] ? kthread_create_on_node+0x120/0x120

Have you seen that every time it takes forever?

Also can you please build your kernel with CONFIG_PROVE_LOCKING and rehang your
machines. lockdep might be able to shed some lights on what's going on here -
something seems to deadlock, which isn't pretty.

The eDP1 probing also looks sane so eDP1 going off doesn't look like a kernel
issue. And indeed in

[   55.008400] [drm:intel_crtc_set_config], [CRTC:3] [FB:39] #connectors=1 (x
y) (1366 0)
[   55.008406] [drm:intel_set_config_compute_mode_changes], modes are
different, full mode set
[   55.008408] [drm:drm_mode_debug_printmodeline], Modeline 24:"1366x768" 60
76300 1366 1414 1446 1610 768 771 776 790 0x48 0xa
[   55.008414] [drm:drm_mode_debug_printmodeline], Modeline 40:"" 0 108000 1280
1328 1440 1688 1024 1025 1028 1066 0x0 0x5
[   55.008420] [drm:intel_set_config_compute_mode_changes], computed changes
for [CRTC:3], mode_changed=1, fb_changed=1
[   55.008424] [drm:intel_modeset_stage_output_state], [CONNECTOR:10:eDP-1] to
[NOCRTC]
[   55.008427] [drm:intel_modeset_stage_output_state], encoder changed, full
mode switch
[   55.008430] [drm:intel_modeset_stage_output_state], encoder changed, full
mode switch
[   55.008433] [drm:intel_modeset_stage_output_state], [CONNECTOR:19:DP-1] to
[CRTC:3]
[   55.008435] [drm:intel_modeset_stage_output_state], crtc changed, full mode
switch
[   55.008437] [drm:intel_modeset_stage_output_state], crtc changed, full mode
switch

we see  that userspace asks for DP1 to be used instead of eDP1. No idea why
running xrandr made things work again earlier. I guess you should try to
reproduce that scenario and grab logs for it.

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