Our fbdev setup requires the device to be awake for access
through the GTT. If one boots without connected displays and
later plugs one in, we won't have any runtime PM references when
the fbdev setup runs. Explicitly grab a runtime PM reference during
the fbdev setup to avoid the following spew:

[   62.518435] RPM wakelock ref not held during HW access
[   62.518459] ------------[ cut here ]------------
[   62.518546] WARNING: CPU: 3 PID: 37 at ../drivers/gpu/drm/i915/intel_drv.h:1800 i915_vma_pin_iomap+0x144/0x150 [i915]
[   62.518585] Modules linked in: i915 i2c_algo_bit drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops drm intel_gtt agpgart netconsole nls_iso8859_1 nls_cp437 vfat fat efi_pstore coretemp hwmon intel_rapl x86_pkg_temp_thermal e1000e efivars ptp pps_core video evdev ip_tables x_tables ipv6 autofs4
[   62.518741] CPU: 3 PID: 37 Comm: kworker/3:1 Not tainted 4.13.0-rc7-skl+ #1077
[   62.518770] Hardware name:                  /NUC7i5BNB, BIOS BNKBL357.86A.0048.2017.0704.1415 07/04/2017
[   62.518827] Workqueue: events i915_hotplug_work_func [i915]
[   62.518853] task: ffff88046c00dc00 task.stack: ffffc90000184000
[   62.518896] RIP: 0010:i915_vma_pin_iomap+0x144/0x150 [i915]
[   62.518919] RSP: 0018:ffffc90000187cc8 EFLAGS: 00010292
[   62.518942] RAX: 000000000000002a RBX: ffff880460044000 RCX: 0000000000000006
[   62.518969] RDX: 0000000000000006 RSI: ffffffff819c3e6f RDI: ffffffff819f1c0e
[   62.518996] RBP: ffffc90000187cd8 R08: ffff88046c00e4f0 R09: 0000000000000000
[   62.519022] R10: ffff8804669ca800 R11: 0000000000000000 R12: ffff880461d20000
[   62.519049] R13: ffffc90000187d48 R14: ffff880461d20000 R15: ffff880460044000
[   62.519076] FS:  0000000000000000(0000) GS:ffff88047ed80000(0000) knlGS:0000000000000000
[   62.519107] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   62.519130] CR2: 000056478ae213f0 CR3: 0000000002c0f000 CR4: 00000000003406e0
[   62.519156] Call Trace:
[   62.519190]  intelfb_create+0x176/0x360 [i915]
[   62.519216]  __drm_fb_helper_initial_config_and_unlock+0x1c7/0x3c0 [drm_kms_helper]
[   62.519251]  drm_fb_helper_hotplug_event.part.18+0xac/0xc0 [drm_kms_helper]
[   62.519282]  drm_fb_helper_hotplug_event+0x1a/0x20 [drm_kms_helper]
[   62.519324]  intel_fbdev_output_poll_changed+0x1a/0x20 [i915]
[   62.519352]  drm_kms_helper_hotplug_event+0x27/0x30 [drm_kms_helper]
[   62.519395]  i915_hotplug_work_func+0x24e/0x2b0 [i915]
[   62.519420]  process_one_work+0x1d3/0x6d0
[   62.519440]  worker_thread+0x4b/0x400
[   62.519458]  ? schedule+0x4a/0x90
[   62.519475]  ? preempt_count_sub+0x97/0xf0
[   62.519495]  kthread+0x114/0x150
[   62.519511]  ? process_one_work+0x6d0/0x6d0
[   62.519530]  ? kthread_create_on_node+0x40/0x40
[   62.519551]  ret_from_fork+0x27/0x40
[   62.519569] Code: c4 78 e6 e0 0f ff e9 08 ff ff ff 80 3d d5 bc 0c 00 00 0f 85 0b ff ff ff 48 c7 c7 d8 50 32 a0 c6 05 c1 bc 0c 00 01 e8 9d 78 e6 e0 <0f> ff e9 f1 fe ff ff 0f 1f 44 00 00 0f 1f 44 00 00 0f b6 87 98
[   62.519771] ---[ end trace 5fbe271f991a58ae ]---
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170901195456.6386-1-ville.syrjala@linux.intel.comReviewed-by: Chris Wilson <chris@chris-wilson.co.uk>