Got kernel panic on clean install of Ubuntu 20.04 LTS with external HDMI display connected to integrated intel graphics adapter in Asustek UX32A laptop

[Norbert]

Steps to reproduce:
1. Download Ubuntu 20.04 LTS installation media
2. Run the installation on the Asustek UX32A laptop without external display connected
3. Finish the installation, boot installed system, install all updates
4. Connect external monitor to the HDMI output of the laptop
5. Boot Ubuntu 20.04 LTS with monitor attached

Expected results:
* Ubuntu founds two screens, user is able to use both of them

Actual results:
* Ubuntu freezes during boot.

Workaround (very ill variant) - boot the system with `nomodeset`. It is ill variant because of single monitor configuration.

It is hard to get logs for the freeze, below is the OCR version of the log obtained with `verbose INIT_VERBOSE=y noplymouth`:

```
[ 43.500044] Hardware name: ASUSTeK COMPUTER INC. UX32A/UX32A. BIOS UX32A.216 02/12/2014
[ 43.5000491 Workqueue: events_unbound_async_run_entry_fn
[ 43.500098] RIP: 0010:intel_disable_pipe+0x1c8/0x1d0 [i915]
[ 43.500099J Code: e9 b2 fe ff fr 31 f6 1c 89 c? e0 23 cb ff ff 18 8d 65 d8 5b 41 5c 41 Sd 41 5e 41 5f 5d c3 40 c7 c7 de b4 44 c0 e8 33 9b 54 fb <0f> 0b e9 63 ff ff ff 90 0f If 44 00 00 55 48 8d 46 30 48 89 cl 18
[ 43.500100] RSP: 0018:ffffb93d400737a0 EFLAGS: 00010286
[ 43.500101] RAX: 0000000000000000 RBX: ffff98ff027c0000 RCX: 0000000000000000
[ 43.500102] RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000202
[ 43.500102] RBP: ffffb93d400737c8 R08: 0000000a20ccb1d7 R09: ffffffffbd394dc4
[ 43.500103] R10: 000000000000041d R11: 000000000002aef0 R12: ffff98ff027c077B
[ 43.500103] R13: ffff98ff120e8000 R14: 0000000000070008 R15: 0000000000000000
[ 43.500105] FS: 0000000000000000(0000) GS:ffff98ff14e00000(0000) knlGS:0000000000000000
[ 43.500105] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000060050033
[ 43.500106] CR2 : 000055ad3bd4f668 CR3: 0000000ld720a005 CR4: 00000000001606f0
[ 43.500107] Call Trace:
[ 43.500153] ironlake_crtc_disable+0x7e/0x540 [i915]
[ 43.500198] intel_atomic_commit_tail+0x261/0x12e0 [i915]
[ 43.500201] ? flush_workqueue_prep_pwqs+0x12e/0x140
[ 43.500245] intel_atomic_commit+0x204/0x2b0 [i915]
[ 43.500267] drm_atomic_commit+0x4a/0x50 [drm]
[ 43.500280] drm_client_modeset_commit_atomic+0x1d0/0x1f0 [drm]
[ 43.500292] drm_client_modeset_commit_force+0x55/0x160 [drm]
[ 43.500361] drm_fb_helper_pan_display+0xfc/0x230 [drm_kms_helper]
[ 43.500348] intel_fbdev_pan_display+0x1b/0x40 [i915]
[ 43.506352] fb_pan_display+0x0c/0x110
[ 43.500353] bit_update_start +0x20/0x50
[ 43.500355] fbcon_switch+0x3e5/0x5d0
[ 43.500359] redraw_screen+0xfe/0x270
[ 43.500360] do_bind_con_driver.cold+0x94/0xe4
[ 43.500362] do_take_over_console+0x12f/0x1a0
[ 43.500364] do_fbcon_takeover+0x5c/0xb0
[ 43.500365] fbcon_fb_registered+0xf4/0x100
[ 43.500366] register_framebuffer+0x207/0x310
[ 43.500373] __drm_fb_helper_initial_config_and_unlock+0x303/0x440 [drm_kms_helper]
[ 43.500379] drm_fb_helper_initial_config+0x36/0x40 [drm_kms_helper]
[ 43.500421] intel_fbdev_initial_config+0x18/0x30 [i915]
[ 43.500425] async_run_entry_fn+0x3c/0x150
[ 43.500426] process_one_work+0x1eb/0x3b0
[ 43.500428] worker_thread+0x4d/0x400
[ 43.500429] kthread+0x104/0x140
[ 43.500431] ? process_one_work+0x3b0/0x3b0
[ 43.500432] ? kthread_park+0x90/0x90
[ 43.500434] ret_from_fork+0x35/0x40
[ 43.500436] --- [ end trace 32c5f2079451ea7c ] ---
[ 44.604015] [drm:ironlake_crtc_enable [i915]] *ERROR* mode set failed: pipe A stuck
[ 54.659975] [drm:drm_atomic_helper_wait_for_flip_done [drm_kms_helper]] *ERROR* [CRTC:42:pipe A] flip_done timed out
[ 54.766978] i915 0000:00:02.0: fb0: i915drmfb frame buffer device
```

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: linux-modules-5.4.0-40-generic 5.4.0-40.44
ProcVersionSignature: Ubuntu 5.4.0-40.44-generic 5.4.44
Uname: Linux 5.4.0-40-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.4
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: mate 1144 F.... pulseaudio
CasperMD5CheckResult: skip
CurrentDesktop: MATE
Date: Fri Jul 17 12:15:08 2020
Dependencies:

MachineType: ASUSTeK COMPUTER INC. UX32A
ProcFB:

ProcKernelCmdLine: BOOT_IMAGE=/@/boot/vmlinuz root=UUID=37959c33-956f-453e-8cc4-2d396e0c0d80 ro rootflags=subvol=@ verbose noplymouth INIT_VERBOSE=y nomodeset
RelatedPackageVersions:
 linux-restricted-modules-5.4.0-40-generic N/A
 linux-backports-modules-5.4.0-40-generic N/A
 linux-firmware 1.187.1
SourcePackage: linux
StagingDrivers: exfat
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 02/12/2014
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: UX32A.216
dmi.board.asset.tag: ATN12345678901234567
dmi.board.name: UX32A
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: 1.0
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: ASUSTeK COMPUTER INC.
dmi.chassis.version: 1.0
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrUX32A.216:bd02/12/2014:svnASUSTeKCOMPUTERINC.:pnUX32A:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnUX32A:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0:
dmi.product.family: UX
dmi.product.name: UX32A
dmi.product.sku: ASUS-NotebookSKU
dmi.product.version: 1.0
dmi.sys.vendor: ASUSTeK COMPUTER INC.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This change was made by a bot.

[Kai-Heng Feng (kaihengfeng)]

Please test latest mainline kernel:
https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.8-rc7/

[Norbert (nrbrtx)]

>Please test latest mainline kernel:
>https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.8-rc7/

It does not help.

[Kai-Heng Feng (kaihengfeng)]

Please file an upstream bug at intel graphics upstream:
https://gitlab.freedesktop.org/drm/intel/wikis/How-to-file-i915-bugs