Comment 19 for bug 1554299

So far I've tried with older kernels installed on my system. I'll try with newer kernels later. And I incorrectly reported my Ubuntu version - it's 14.04.4 now, and I think the error did not appear on 14.04.3.

3.13 and 3.19: the GL window freezes as described, but the i915 error is not printed in dmesg.

4.2.0-27 and 4.2.0-30: the GL window freezes as described, and this error is printed in dmesg and on VT1 every time I switch from Unity to VT1:

[ 54.481549] [drm:intel_pipe_config_compare [i915]] *ERROR* mismatch in dpll_hw_state.wrpll (expected 0xb018080f, found 0x00000000)
[ 54.481550] ------------[ cut here ]------------
[ 54.481563] WARNING: CPU: 2 PID: 1877 at /build/linux-lts-wily-Vv6Eyd/linux-lts-wily-4.2.0/drivers/gpu/drm/i915/intel_display.c:12328 check_crtc_state+0x282/0x3f0 [i915]()
[ 54.481564] pipe state doesn't match!
[ 54.481565] Modules linked in: ip6table_filter ip6_tables nvram xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack xt_tcpudp bridge stp llc iptable_filter ip_tables x_tables autofs4 uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_core v4l2_common videodev media snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic xpad ff_memless rfcomm bnep bluetooth joydev dell_wmi sparse_keymap nfsd auth_rpcgss nfs_acl dell_laptop dcdbas nfs arc4 dell_smm_hwmon lockd grace snd_hda_intel iwldvm sunrpc intel_rapl snd_hda_codec x86_pkg_temp_thermal binfmt_misc mac80211 fscache intel_powerclamp coretemp amdkfd snd_hda_core amd_iommu_v2 kvm_intel snd_hwdep snd_soc_rt5640 snd_soc_rl6231 snd_seq_midi radeon snd_soc_core i915 snd_seq_midi_event kvm iwlwifi snd_compress snd_rawmidi ac97_bus snd_pcm_dmaengine snd_pcm crct10dif_pclmul crc32_pclmul ttm aesni_intel snd_seq aes_x86_64 drm_kms_helper lrw gf128mul glue_helper ablk_helper cryptd snd_seq_device snd_timer input_leds drm cfg80211 serio_raw snd ie31200_edac mei_me mei i2c_algo_bit lpc_ich soundcore i2c_hid shpchp edac_core i2c_designware_platform wmi dw_dmac i2c_designware_core dw_dmac_core dell_smo8800 snd_soc_sst_acpi 8250_fintek video 8250_dw spi_pxa2xx_platform dell_rbtn mac_hid parport_pc ppdev lp parport hid_generic usbhid hid psmouse e1000e ahci libahci sdhci_pci ptp pps_core sdhci_acpi sdhci
[ 54.481629] CPU: 2 PID: 1877 Comm: Xorg Tainted: G W 4.2.0-27-generic #32~14.04.1-Ubuntu
[ 54.481630] Hardware name: Dell Inc. Latitude E6540/0CYT5F, BIOS A16 09/01/2015
[ 54.481631] ffffffffc061ed00 ffff88020ad0b7f8 ffffffff817b5013 0000000000000000
[ 54.481634] ffff88020ad0b848 ffff88020ad0b838 ffffffff8107792a ffff88020ad0b838
[ 54.481636] ffff880036419b48 ffff88020ad0b8d0 ffff880036419800 ffff880219dc2000
[ 54.481639] Call Trace:
[ 54.481642] [<ffffffff817b5013>] dump_stack+0x45/0x57
[ 54.481645] [<ffffffff8107792a>] warn_slowpath_common+0x8a/0xc0
[ 54.481647] [<ffffffff810779a6>] warn_slowpath_fmt+0x46/0x50
[ 54.481661] [<ffffffffc05b102b>] ? intel_pipe_config_compare+0xaab/0xcc0 [i915]
[ 54.481675] [<ffffffffc05b14c2>] check_crtc_state+0x282/0x3f0 [i915]
[ 54.481692] [<ffffffffc05c4b52>] intel_modeset_check_state+0x292/0x6b0 [i915]
[ 54.481707] [<ffffffffc05c5b9a>] intel_crtc_set_config+0x3ea/0x5a0 [i915]
[ 54.481718] [<ffffffffc035a3a8>] drm_mode_set_config_internal+0x68/0x100 [drm]
[ 54.481729] [<ffffffffc035e2cd>] drm_mode_setcrtc+0xdd/0x4f0 [drm]
[ 54.481737] [<ffffffffc034f6c3>] drm_ioctl+0x363/0x680 [drm]
[ 54.481747] [<ffffffffc035e1f0>] ? drm_mode_setplane+0x1c0/0x1c0 [drm]
[ 54.481751] [<ffffffff811fdfbd>] do_vfs_ioctl+0x2cd/0x4b0
[ 54.481753] [<ffffffff811ed825>] ? __sb_end_write+0x35/0x70
[ 54.481755] [<ffffffff811eb51c>] ? vfs_write+0x15c/0x190
[ 54.481758] [<ffffffff811fe219>] SyS_ioctl+0x79/0x90
[ 54.481761] [<ffffffff817bc3b2>] entry_SYSCALL_64_fastpath+0x16/0x75
[ 54.481763] ---[ end trace 5cee9101c23cf574 ]---