Hey,

this just popped up in the dmesg of my Dell XPS 13 -- the system seems to
run well, but still, it asks about being cut and sent, so here it is. It is
on 4.1.0-rc4+ (Linus' tree as of May 24th, around 3pm UTC -- don't have the
git commit ID anymore).

------------[ cut here ]------------
WARNING: CPU: 0 PID: 1167 at /home/brodo/local/kernel/git/linux/drivers/gpu/drm/i915/intel_uncore.c:566 hsw_unclaimed_reg_debug+0x7d/0xa0()
Unclaimed register detected before reading register 0x130040
Modules linked in:
CPU: 0 PID: 1167 Comm: Xorg Not tainted 4.1.0-rc4+ #1
Hardware name: Dell Inc. XPS 13 9343/0TM99H, BIOS A03 03/25/2015
 ffffffffb39694d8 ffff88020e14b998 ffffffffb322906f 0000000080000001
 ffff88020e14b9e8 ffff88020e14b9d8 ffffffffb272ca8a ffff88020e14b9a8
 ffff880215190000 0000000000130040 ffff880215bfd800 0000000000130040
Call Trace:
 [<ffffffffb322906f>] dump_stack+0x4f/0x7b
 [<ffffffffb272ca8a>] warn_slowpath_common+0x8a/0xc0
 [<ffffffffb272cb06>] warn_slowpath_fmt+0x46/0x50
 [<ffffffffb2be63cd>] hsw_unclaimed_reg_debug+0x7d/0xa0
 [<ffffffffb2be84b6>] gen6_read32+0x56/0x1c0
 [<ffffffffb2c096e6>] hsw_disable_pc8+0x36/0x2c0
 [<ffffffffb2b98e60>] intel_runtime_resume+0x160/0x1b0
 [<ffffffffb2a94bdf>] pci_pm_runtime_resume+0x7f/0xc0
 [<ffffffffb2a94b60>] ? pci_restore_standard_config+0x50/0x50
 [<ffffffffb2c5c8f6>] __rpm_callback+0x36/0x90
 [<ffffffffb2c5c976>] rpm_callback+0x26/0xa0
 [<ffffffffb2c5dcc6>] rpm_resume+0x496/0x670
 [<ffffffffb2756209>] ? preempt_count_add+0x79/0xc0
 [<ffffffffb2c5dee0>] __pm_runtime_resume+0x40/0x60
 [<ffffffffb2ba7fd5>] intel_runtime_pm_get+0x55/0x80
 [<ffffffffb2bc6989>] i915_gem_free_object+0x29/0x360
 [<ffffffffb2b6b417>] drm_gem_object_free+0x27/0x40
 [<ffffffffb2b6b548>] drm_gem_object_handle_unreference_unlocked+0x118/0x130
 [<ffffffffb2b6b6d4>] drm_gem_handle_delete+0xb4/0x100
 [<ffffffffb2fde8ab>] ? sock_recvmsg+0x3b/0x50
 [<ffffffffb2b6ba95>] drm_gem_close_ioctl+0x25/0x30
 [<ffffffffb2b6c4a5>] drm_ioctl+0x1a5/0x6a0
 [<ffffffffb2869672>] ? do_readv_writev+0x1b2/0x260
 [<ffffffffb323187a>] ? _raw_spin_unlock_irqrestore+0x2a/0x60
 [<ffffffffb2a5b804>] ? timerqueue_del+0x24/0x70
 [<ffffffffb278b2fe>] ? __remove_hrtimer+0x4e/0xe0
 [<ffffffffb287c110>] do_vfs_ioctl+0x2e0/0x4e0
 [<ffffffffb2886482>] ? __fget+0x72/0xb0
 [<ffffffffb287c391>] SyS_ioctl+0x81/0xa0
 [<ffffffffb3232017>] system_call_fastpath+0x12/0x6a
---[ end trace 8ff5864d3e587195 ]---

Best,
	Dominik