Hi first post here... Just wanted to chime in and confirm same bug on same machine: Thinkpad x260 Processor: Intel® Core™ i7-6500U CPU @ 2.50GHz × 4 Graphics: Gallium 0.4 on llvmpipe (LLVM 3.8, 256 bits) In order to try and fix the bug I have added the repo: http://ppa.launchpad.net/oibaf/graphics-drivers/ubuntu Before this change, the system reported Graphics: Intel Skylake HD Graphics 520 I'm running a 1 day old Ubuntu 16.04. I have experienced this crash on the stock kernel, 4.6.9 and 4.6.3 My steps to reproduce: * plug in HDMI to a 4K external display and set display to full resolution (this will only have a frame rate of 30Hz due to a limitation in HDMI standard) * turn off laptop monitor * plug in DP to *the same* external display * Set new configuration where HDMI if off and DP is on. (this will be at 60Hz) * screen goes blank on both HDMI and DP source. reverts to last configuration because of crash. I believe it is the combination of 4K display in full resolution *and* 60hz. This would be why the crash is only seen with DP at full resolution. last crash report with kernel 4.6.3: Jul 06 19:32:14 emil-workpad kernel: ------------[ cut here ]------------ Jul 06 19:32:14 emil-workpad kernel: WARNING: CPU: 0 PID: 986 at /home/kernel/COD/linux/drivers/gpu/drm/i915/intel_display.c:13938 skl_max_scale.part.99+0x6d/0x80 [i915] Jul 06 19:32:14 emil-workpad kernel: WARN_ON_ONCE(!crtc_clock || cdclk < crtc_clock) Jul 06 19:32:14 emil-workpad kernel: Modules linked in: Jul 06 19:32:14 emil-workpad kernel: rfcomm bnep arc4 snd_soc_skl snd_soc_skl_ipc snd_hda_codec_hdmi snd_soc_sst_ipc snd_soc_sst_dsp snd_hda_ext_core snd_hda_codec_realtek snd_hda_codec_generic snd_soc_sst_match intel_rapl snd_soc_core x86_pkg_temp_thermal snd_compress inte Jul 06 19:32:14 emil-workpad kernel: hid_lenovo usbhid hid rtsx_pci_sdmmc crct10dif_pclmul crc32_pclmul ghash_clmulni_intel i915 aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd i2c_algo_bit drm_kms_helper syscopyarea sysfillrect e1000e sysimgblt psmouse f Jul 06 19:32:14 emil-workpad kernel: CPU: 0 PID: 986 Comm: Xorg Tainted: G W 4.6.3-040603-generic #201606241434 Jul 06 19:32:14 emil-workpad kernel: Hardware name: LENOVO 20F6006XMD/20F6006XMD, BIOS R02ET44W (1.17 ) 01/25/2016 Jul 06 19:32:14 emil-workpad kernel: 0000000000000286 00000000eeed4400 ffff8802148b7a50 ffffffff813f3373 Jul 06 19:32:14 emil-workpad kernel: ffff8802148b7aa0 0000000000000000 ffff8802148b7a90 ffffffff8108293b Jul 06 19:32:14 emil-workpad kernel: 00003672c02dada0 ffff8802183dba80 ffff880035c4e800 ffff8800b29cb000 Jul 06 19:32:14 emil-workpad kernel: Call Trace: Jul 06 19:32:14 emil-workpad kernel: [] dump_stack+0x63/0x90 Jul 06 19:32:14 emil-workpad kernel: [] __warn+0xcb/0xf0 Jul 06 19:32:14 emil-workpad kernel: [] warn_slowpath_fmt+0x5f/0x80 Jul 06 19:32:14 emil-workpad kernel: [] skl_max_scale.part.99+0x6d/0x80 [i915] Jul 06 19:32:14 emil-workpad kernel: [] intel_check_primary_plane+0xc0/0xe0 [i915] Jul 06 19:32:14 emil-workpad kernel: [] ? intel_ddi_compute_config+0x5a/0xc0 [i915] Jul 06 19:32:14 emil-workpad kernel: [] intel_plane_atomic_check+0x12e/0x1f0 [i915] Jul 06 19:32:14 emil-workpad kernel: [] drm_atomic_helper_check_planes+0x48/0x1d0 [drm_kms_helper] Jul 06 19:32:14 emil-workpad kernel: [] intel_atomic_check+0x172/0x830 [i915] Jul 06 19:32:14 emil-workpad kernel: [] drm_atomic_check_only+0x181/0x600 [drm] Jul 06 19:32:14 emil-workpad kernel: [] ? drm_atomic_set_crtc_for_connector+0x57/0xe0 [drm] Jul 06 19:32:14 emil-workpad kernel: [] drm_atomic_commit+0x17/0x60 [drm] Jul 06 19:32:14 emil-workpad kernel: [] drm_atomic_helper_set_config+0x7a/0xb0 [drm_kms_helper] Jul 06 19:32:14 emil-workpad kernel: [] drm_mode_set_config_internal+0x62/0x100 [drm] Jul 06 19:32:14 emil-workpad kernel: [] drm_mode_setcrtc+0x3e0/0x500 [drm] Jul 06 19:32:14 emil-workpad kernel: [] drm_ioctl+0x152/0x540 [drm] Jul 06 19:32:14 emil-workpad kernel: [] ? drm_mode_setplane+0x1b0/0x1b0 [drm] Jul 06 19:32:14 emil-workpad kernel: [] do_vfs_ioctl+0xa1/0x5b0 Jul 06 19:32:14 emil-workpad kernel: [] ? __set_task_blocked+0x41/0xa0 Jul 06 19:32:14 emil-workpad kernel: [] ? __set_current_blocked+0x36/0x60 Jul 06 19:32:14 emil-workpad kernel: [] SyS_ioctl+0x79/0x90 Jul 06 19:32:14 emil-workpad kernel: [] entry_SYSCALL_64_fastpath+0x1e/0xa8 Jul 06 19:32:14 emil-workpad kernel: ---[ end trace dce1bcd4b56b9a53 ]--- Jul 06 19:32:14 emil-workpad kernel: [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe A FIFO underrun