xorg-server 1.18.3
xf86-video-intel 2.99.917

I was trying to get my Haswell (the one with the disabled TSX instructions in the firmware) to work at the audio on the Radeon TAHITI was stuffed https://bugs.freedesktop.org/show_bug.cgi?id=92889 and I found that the first time I started X I would get an exception with the error compute_config() on unknown output!.

On the second attempt (ie. starting X remotely, this error would not appear). I dug a bit further and tried a different kernel and discovered that without the fb.ko and the legacy (since 4.4) option enabled ie:

  Enable legacy fbdev support for your modesetting driver (DRM_FBDEV_EMULATION) [Y/n/?] (NEW) 

I would get the following errors and no X:

Jun 22 23:00:16 at kernel: WARNING: CPU: 2 PID: 699 at drivers/gpu/drm/i915/intel_ddi.c:3216 intel_ddi_compute_config+0x64/0x90 [i915]
Jun 22 23:00:16 at kernel: compute_config() on unknown output!
Jun 22 23:00:16 at kernel: Modules linked in: snd_hda_codec_hdmi af_packet fuse btrfs raid6_pq xor ip6table_nat nf_nat_ipv6 ip6table_mangle nf_log_ipv6 nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables xt_length nf_log_ipv4 nf_log_common xt_LOG xt_owner xt_recen
Jun 22 23:00:16 at kernel:  mei_me snd_timer i2c_core snd soundcore ptp mei pps_core thermal fan evdev video backlight acpi_pad processor sch_fq_codel kvm_intel kvm irqbypass efi_pstore efivars efivarfs ip_tables x_tables unix ipv6 autofs4 raid10 raid0 md_mod nls_utf8 nls
Jun 22 23:00:16 at kernel: CPU: 2 PID: 699 Comm: Xorg Not tainted 4.6.2+ #2
Jun 22 23:00:16 at kernel: Hardware name: ASUS All Series/Z97M-PLUS, BIOS 2903 02/22/2016
Jun 22 23:00:16 at kernel:  0000000000000000 ffffffffa43c3335 ffff8800a75fbb68 0000000000000000
Jun 22 23:00:16 at kernel:  ffffffffa4048ba4 ffff880806301000 ffff8800a75fbbb8 ffff8800a75cac00
Jun 22 23:00:16 at kernel:  0000000000000003 ffff8800a75cac00 ffff8807fcaae000 ffffffffa4048c0a
Jun 22 23:00:16 at kernel: Call Trace:
Jun 22 23:00:16 at kernel:  [<ffffffffa43c3335>] ? dump_stack+0x46/0x59
Jun 22 23:00:16 at kernel:  [<ffffffffa4048ba4>] ? __warn+0xb4/0xd0
Jun 22 23:00:16 at kernel:  [<ffffffffa4048c0a>] ? warn_slowpath_fmt+0x4a/0x50
Jun 22 23:00:16 at kernel:  [<ffffffffc0b062b4>] ? intel_ddi_compute_config+0x64/0x90 [i915]
Jun 22 23:00:16 at kernel:  [<ffffffffc0aecd23>] ? intel_atomic_check+0x213/0x1120 [i915]
Jun 22 23:00:16 at kernel:  [<ffffffffc07ac991>] ? drm_atomic_check_only+0x181/0x600 [drm]
Jun 22 23:00:16 at kernel:  [<ffffffffc07ac1bc>] ? drm_atomic_set_crtc_for_connector+0x4c/0xd0 [drm]
Jun 22 23:00:16 at kernel:  [<ffffffffc07ace1d>] ? drm_atomic_commit+0xd/0x50 [drm]
Jun 22 23:00:16 at kernel:  [<ffffffffc08c3ed1>] ? drm_atomic_helper_set_config+0x71/0xa0 [drm_kms_helper]
Jun 22 23:00:16 at kernel:  [<ffffffffc079e2a9>] ? drm_mode_set_config_internal+0x59/0xf0 [drm]
Jun 22 23:00:16 at kernel:  [<ffffffffc07a1d56>] ? drm_mode_setcrtc+0x3a6/0x4c0 [drm]
Jun 22 23:00:16 at kernel:  [<ffffffffc0794549>] ? drm_ioctl+0x119/0x480 [drm]
Jun 22 23:00:16 at kernel:  [<ffffffffc07a19b0>] ? drm_mode_setplane+0x1b0/0x1b0 [drm]
Jun 22 23:00:16 at kernel:  [<ffffffffa414c308>] ? do_vfs_ioctl+0x88/0x5a0
Jun 22 23:00:16 at kernel:  [<ffffffffa403cf1a>] ? __do_page_fault+0x1ba/0x430
Jun 22 23:00:16 at kernel:  [<ffffffffa40528c1>] ? recalc_sigpending+0x11/0x40
Jun 22 23:00:16 at kernel:  [<ffffffffa41557eb>] ? __fget+0x6b/0xb0
Jun 22 23:00:16 at kernel:  [<ffffffffa414c856>] ? SyS_ioctl+0x36/0x70
Jun 22 23:00:16 at kernel:  [<ffffffffa43c991f>] ? entry_SYSCALL_64_fastpath+0x17/0x93
Jun 22 23:00:16 at kernel: ---[ end trace 970a6255bbc1e54b ]---
Jun 22 23:00:16 at kernel: ------------[ cut here ]------------
Jun 22 23:00:16 at kernel: WARNING: CPU: 2 PID: 699 at drivers/gpu/drm/i915/intel_dp.c:150 intel_dp_max_link_bw+0x24/0x40 [i915]
Jun 22 23:00:16 at kernel: invalid max DP link bw val 0, using 1.62Gbps
Jun 22 23:00:16 at kernel: Modules linked in: snd_hda_codec_hdmi af_packet fuse btrfs raid6_pq xor ip6table_nat nf_nat_ipv6 ip6table_mangle nf_log_ipv6 nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables xt_length nf_log_ipv4 nf_log_common xt_LOG xt_owner xt_recen
Jun 22 23:00:16 at kernel:  mei_me snd_timer i2c_core snd soundcore ptp mei pps_core thermal fan evdev video backlight acpi_pad processor sch_fq_codel kvm_intel kvm irqbypass efi_pstore efivars efivarfs ip_tables x_tables unix ipv6 autofs4 raid10 raid0 md_mod nls_utf8 nls
Jun 22 23:00:16 at kernel: CPU: 2 PID: 699 Comm: Xorg Tainted: G        W       4.6.2+ #2
Jun 22 23:00:16 at kernel: Hardware name: ASUS All Series/Z97M-PLUS, BIOS 2903 02/22/2016
Jun 22 23:00:16 at kernel:  0000000000000000 ffffffffa43c3335 ffff8800a75fbaa0 0000000000000000
Jun 22 23:00:16 at kernel:  ffffffffa4048ba4 ffff8808063010d8 ffff8800a75fbaf0 ffff880806301000
Jun 22 23:00:16 at kernel:  0000000000000004 0000000000000003 ffff8807fcaae000 ffffffffa4048c0a
Jun 22 23:00:16 at kernel: Call Trace:
Jun 22 23:00:16 at kernel:  [<ffffffffa43c3335>] ? dump_stack+0x46/0x59
Jun 22 23:00:16 at kernel:  [<ffffffffa4048ba4>] ? __warn+0xb4/0xd0
Jun 22 23:00:16 at kernel:  [<ffffffffa4048c0a>] ? warn_slowpath_fmt+0x4a/0x50
Jun 22 23:00:16 at kernel:  [<ffffffffa43c2a4d>] ? printk+0x43/0x4b
Jun 22 23:00:16 at kernel:  [<ffffffffc0b0b994>] ? intel_dp_max_link_bw+0x24/0x40 [i915]
Jun 22 23:00:16 at kernel:  [<ffffffffc0b1008f>] ? intel_dp_common_rates+0x1f/0xc0 [i915]
Jun 22 23:00:16 at kernel:  [<ffffffffc0b10910>] ? intel_dp_compute_config+0x90/0x700 [i915]
Jun 22 23:00:16 at kernel:  [<ffffffffa4048b7a>] ? __warn+0x8a/0xd0
Jun 22 23:00:16 at kernel:  [<ffffffffa4048c0a>] ? warn_slowpath_fmt+0x4a/0x50
Jun 22 23:00:16 at kernel:  [<ffffffffc0b06291>] ? intel_ddi_compute_config+0x41/0x90 [i915]
Jun 22 23:00:16 at kernel:  [<ffffffffc0aecd23>] ? intel_atomic_check+0x213/0x1120 [i915]
Jun 22 23:00:16 at kernel:  [<ffffffffc07ac991>] ? drm_atomic_check_only+0x181/0x600 [drm]
Jun 22 23:00:16 at kernel:  [<ffffffffc07ac1bc>] ? drm_atomic_set_crtc_for_connector+0x4c/0xd0 [drm]
Jun 22 23:00:16 at kernel:  [<ffffffffc07ace1d>] ? drm_atomic_commit+0xd/0x50 [drm]
Jun 22 23:00:16 at kernel:  [<ffffffffc08c3ed1>] ? drm_atomic_helper_set_config+0x71/0xa0 [drm_kms_helper]
Jun 22 23:00:16 at kernel:  [<ffffffffc079e2a9>] ? drm_mode_set_config_internal+0x59/0xf0 [drm]
Jun 22 23:00:16 at kernel:  [<ffffffffc07a1d56>] ? drm_mode_setcrtc+0x3a6/0x4c0 [drm]
Jun 22 23:00:16 at kernel:  [<ffffffffc0794549>] ? drm_ioctl+0x119/0x480 [drm]
Jun 22 23:00:16 at kernel:  [<ffffffffc07a19b0>] ? drm_mode_setplane+0x1b0/0x1b0 [drm]
Jun 22 23:00:16 at kernel:  [<ffffffffa414c308>] ? do_vfs_ioctl+0x88/0x5a0
Jun 22 23:00:16 at kernel:  [<ffffffffa403cf1a>] ? __do_page_fault+0x1ba/0x430
Jun 22 23:00:16 at kernel:  [<ffffffffa40528c1>] ? recalc_sigpending+0x11/0x40
Jun 22 23:00:16 at kernel:  [<ffffffffa41557eb>] ? __fget+0x6b/0xb0
Jun 22 23:00:16 at kernel:  [<ffffffffa414c856>] ? SyS_ioctl+0x36/0x70
Jun 22 23:00:16 at kernel:  [<ffffffffa43c991f>] ? entry_SYSCALL_64_fastpath+0x17/0x93
Jun 22 23:00:16 at kernel: ---[ end trace 970a6255bbc1e54c ]---
Jun 22 23:00:16 at /usr/libexec/gdm-x-session[697]: (EE) intel(0): failed to set mode: Invalid argument [22]
Jun 22 23:00:16 at kernel: ------------[ cut here ]------------


There should be no dependency on any of the FB code.  If you mark this as a DUP of  https://bugs.freedesktop.org/show_bug.cgi?id=68463 then this problem has been around for three years. Unacceptable Intel. Shame on you