on the yoga 2 851f tablet I am also trying often to get KMS working but like with the 3.19.y branch still no luck. I am using vanilla kernels, and also with one or two patches of /from the fedlet image derived. here the short debug from linux-stable v4.0.0 (and all previous versions like rc1 till rc7 too) BOOT_IMAGE=/vmlinuz-4.0.0.6 root=UUID=6c3bcf92-5a26-4dde-95e3-78ceb9aaa35b ro i915.modeset=1 rhgb quiet LANG=de_DE.UTF-8 i915.force_backlight_pmic=1 lshw: *-display description: VGA compatible controller product: Atom Processor Z36xxx/Z37xxx Series Graphics & Display vendor: Intel Corporation physical id: 2 bus info: pci@0000:00:02.0 version: 0d width: 32 bits clock: 33MHz capabilities: pm msi vga_controller bus_master cap_list rom configuration: driver=i915 latency=0 resources: irq:205 memory:90000000-903fffff memory:80000000-8fffffff ioport:1000(size=8) lspci: 00:02.0 VGA compatible controller: Intel Corporation Atom Processor Z36xxx/Z37xxx Series Graphics & Display (rev 0d) (prog-if 00 [VGA controller]) Subsystem: Intel Corporation Device 7270 Flags: bus master, fast devsel, latency 0, IRQ 205 Memory at 90000000 (32-bit, non-prefetchable) [size=4M] Memory at 80000000 (32-bit, prefetchable) [size=256M] I/O ports at 1000 [size=8] Expansion ROM at [disabled] Capabilities: [d0] Power Management version 2 Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit- Capabilities: [b0] Vendor Specific Information: Len=07 Kernel driver in use: i915 snap of dmesg: [ 1.275627] [drm] Initialized drm 1.1.0 20060810 [ 1.277552] [drm] Memory usable by graphics device = 2048M [ 1.277574] checking generic (80000000 8ca000) vs hw (80000000 10000000) [ 1.277579] fb: switching to inteldrmfb from simple [ 1.277631] Console: switching to colour dummy device 80x25 [ 1.277848] [drm] Replacing VGA console driver [ 1.279567] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013). [ 1.279573] [drm] Driver supports precise vblank timestamp query. [ 1.279600] [drm:intel_parse_bios] *ERROR* Unknown element [ 1.279611] [drm:intel_parse_bios] *ERROR* Sequence elements going beyond block itself. Sequence block parsing failed [ 1.317468] vgaarb: device changed decodes: PCI:0000:00:02.0,olddecodes=io+mem,decodes=io+mem:owns=io+mem [ 1.331700] ACPI: Video Device [GFX0] (multi-head: yes rom: no post: no) [ 1.332138] input: Video Bus as /devices/LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/LNXVIDEO:00/input/input1 [ 1.332227] [drm] Initialized i915 1.6.0 20150130 for 0000:00:02.0 on minor 0 ... [ 1.388711] [drm] GMBUS [i915 gmbus dpb] timed out, falling back to bit banging on pin 5 [ 1.402951] fbcon: inteldrmfb (fb0) is primary device [ 2.382620] i8042: No controller found [ 2.382647] Switched to clocksource tsc [ 2.382801] mousedev: PS/2 mouse device common for all mice [ 2.383565] ACPI Warning: Could not enable fixed event - RealTimeClock (4) (20150204/evxface-654) [ 2.383878] rtc_cmos 00:00: rtc core: registered rtc_cmos as rtc0 [ 2.384137] rtc_cmos: probe of 00:00 failed with error -22 ... [ 2.564883] Console: switching to colour frame buffer device 150x120 [ 2.597839] i915 0000:00:02.0: fb0: inteldrmfb frame buffer device [ 2.597842] i915 0000:00:02.0: registered panic notifier [ 2.603428] Freeing unused kernel memory: 784K (c0ed1000 - c0f95000) ... [ 3.689692] usb 1-1.2.3: Product: Dell USB Keyboard [ 3.689696] usb 1-1.2.3: Manufacturer: Dell [ 3.690069] usb 1-1.2.3: ep 0x81 - rounding interval to 128 microframes, ep desc says 192 microframes [ 3.696168] input: Dell Dell USB Keyboard as /devices/pci0000:00/0000:00:14.0/usb1/1-1/1-1.2/1-1.2.3/1-1.2.3:1.0/0003:413C:2003.0002/input/input3 [ 3.747717] hid-generic 0003:413C:2003.0002: input,hidraw1: USB HID v1.10 Keyboard [Dell Dell USB Keyboard] on usb-0000:00:14.0-1.2.3/input0 [ 3.753699] ax88179_178a 1-1.3:1.0 eth0: register 'ax88179_178a' at usb-0000:00:14.0-1.3, ASIX AX88179 USB 3.0 Gigabit Ethernet, 00:fe:c8:f7:bc:d 9 [ 3.753760] usbcore: registered new interface driver ax88179_178a [ 3.757735] ax88179_178a 1-1.3:1.0 enp0s20u1u3: renamed from eth0 [ 3.838426] ------------[ cut here ]------------ [ 3.838467] WARNING: CPU: 2 PID: 264 at drivers/gpu/drm/drm_irq.c:1138 drm_wait_one_vblank+0x177/0x180() [ 3.838479] vblank wait timed out on crtc 0 [ 3.838488] Modules linked in: ax88179_178a usbnet mii [ 3.838526] CPU: 2 PID: 264 Comm: plymouthd Not tainted 4.0.0.6 #81 [ 3.838537] Hardware name: LENOVO 60072/INVALID, BIOS 02WT18WW 08/01/2014 [ 3.838548] c0e31947 d6eaedba 00000000 f689bc70 c0b13585 f689bcb0 f689bca0 c0449d57 [ 3.838585] c0d9d7f8 f689bcd0 00000108 c0d7050b 00000472 c07cbe57 c07cbe57 00000000 [ 3.838620] f4b77800 00000000 f689bcbc c0449dce 00000009 f689bcb0 c0d9d7f8 f689bcd0 [ 3.838656] Call Trace: [ 3.838685] [] dump_stack+0x41/0x52 [ 3.838710] [] warn_slowpath_common+0x87/0xc0 [ 3.838731] [] ? drm_wait_one_vblank+0x177/0x180 [ 3.838750] [] ? drm_wait_one_vblank+0x177/0x180 [ 3.838771] [] warn_slowpath_fmt+0x3e/0x60 [ 3.838791] [] drm_wait_one_vblank+0x177/0x180 [ 3.838815] [] ? prepare_to_wait_event+0xc0/0xc0 [ 3.838835] [] drm_crtc_wait_one_vblank+0x19/0x20 [ 3.838857] [] drm_plane_helper_commit+0x24a/0x280 [ 3.838878] [] drm_plane_helper_update+0x78/0xc0 [ 3.838898] [] intel_crtc_set_config+0xa1c/0xde0 [ 3.838922] [] drm_mode_set_config_internal+0x4e/0xc0 [ 3.838942] [] drm_mode_setcrtc+0xc6/0x5a0 [ 3.838963] [] ? drm_mode_setplane+0x230/0x230 [ 3.838982] [] drm_ioctl+0x1cf/0x520 [ 3.839004] [] ? kmem_cache_alloc_trace+0x175/0x1e0 [ 3.839024] [] ? free_hot_cold_page_list+0x42/0x90 [ 3.839043] [] ? drm_mode_setplane+0x230/0x230 [ 3.839065] [] ? af_alg_cmsg_send+0xc2/0xd0 [ 3.839089] [] ? drm_getmap+0xc0/0xc0 [ 3.839130] [] do_vfs_ioctl+0x30a/0x510 [ 3.839151] [] ? inode_has_perm.isra.34+0x32/0x40 [ 3.839170] [] ? file_has_perm+0x97/0xa0 [ 3.839191] [] ? selinux_file_ioctl+0x4c/0xf0 [ 3.839212] [] SyS_ioctl+0x60/0x90 [ 3.839240] [] ? af_alg_cmsg_send+0xc2/0xd0 [ 3.839260] [] ? af_alg_cmsg_send+0xc2/0xd0 [ 3.839280] [] sysenter_do_call+0x12/0x12 [ 3.839300] [] ? af_alg_cmsg_send+0xc2/0xd0 [ 3.839319] [] ? af_alg_cmsg_send+0xc2/0xd0 [ 3.839334] ---[ end trace 409865246eac131f ]--- and after that I tried a build with the merge of intel-drm-nightly like it was suggested in comment 13 on this bug https://bugzilla.kernel.org/show_bug.cgi?id=92171