Created attachment 138748 [details]
the dmesg

I have an AMD Ryzen 5 2500U with Radeon Vega Mobile Gfx laptop.

After system is booted and plugged the HDMI cable, the laptop's display had been blurred a while than came back again, and the extended display also worked.
However, I can see the amdgpu module hits the error in dmesg: "[drm:generic_reg_wait [amdgpu]] *ERROR* REG_WAIT timeout 1us * 10 tries - optc1_lock line:553" and the warning message.

[   70.999928] amdgpu 0000:03:00.0: ring 12(vcn_enc0) uses VM inv eng 6 on hub 1
[   70.999964] amdgpu 0000:03:00.0: ring 13(vcn_enc1) uses VM inv eng 7 on hub 1
[   71.005998] [drm] Initialized amdgpu 3.23.0 20150101 for 0000:03:00.0 on minor 0
[   88.313107] Bluetooth: RFCOMM TTY layer initialized
[   88.313115] Bluetooth: RFCOMM socket layer initialized
[   88.313120] Bluetooth: RFCOMM ver 1.11
[   99.918971] rfkill: input handler disabled
[  129.028256] [drm:generic_reg_wait [amdgpu]] *ERROR* REG_WAIT timeout 1us * 10 tries - optc1_lock line:553
[  129.028302] WARNING: CPU: 0 PID: 943 at drivers/gpu/drm/amd/amdgpu/../display/dc/dc_helper.c:195 generic_reg_wait+0xeb/0x160 [amdgpu]
[  129.028303] Modules linked in: rfcomm amdkfd amd_iommu_v2 amdgpu chash gpu_sched ttm drm_kms_helper drm i2c_algo_bit fb_sys_fops syscopyarea sysfillrect sysimgblt ccm cmac bnep zram arc4 snd_hda_codec_generic snd_hda_codec_hdmi snd_hda_intel snd_hda_codec snd_hda_core snd_hwdep iwlmvm snd_pcm uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_v4l2 edac_mce_amd snd_timer mac80211 videobuf2_common videodev media asus_nb_wmi asus_wmi wmi_bmof kvm_amd ccp kvm irqbypass crct10dif_pclmul crc32_pclmul ghash_clmulni_intel snd btusb btrtl r8169 btbcm pcbc btintel mii aesni_intel sparse_keymap soundcore iwlwifi bluetooth ecdh_generic cfg80211 joydev input_leds shpchp aes_x86_64 crypto_simd glue_helper cryptd i2c_piix4 wmi mac_hid tpm_crb asus_wireless ip_tables x_tables uas usb_storage hid_multitouch hid_generic
[  129.028342]  serio_raw ahci libahci video i2c_hid hid
[  129.028348] CPU: 0 PID: 943 Comm: Xorg Not tainted 4.16.0 #9
[  129.028349] Hardware name: ASUSTeK COMPUTER INC. VivoBook 15 X505ZA/X505ZA, BIOS X505ZA.200.T08 02/03/2018
[  129.028380] RIP: 0010:generic_reg_wait+0xeb/0x160 [amdgpu]
[  129.028382] RSP: 0018:ffffafa98204b840 EFLAGS: 00010297
[  129.028383] RAX: 0000000000000229 RBX: 000000000000000b RCX: 0000000000000000
[  129.028385] RDX: 0000000000000000 RSI: ffff8b5e536164b8 RDI: ffff8b5e536164b8
[  129.028386] RBP: ffffafa98204b880 R08: 0000000000006e60 R09: 00000000000003ad
[  129.028387] R10: 0000000000000001 R11: ffffffffa43527ed R12: 0000000000000001
[  129.028388] R13: ffff8b5e50f1b880 R14: 0000000000000100 R15: 0000000000000001
[  129.028390] FS:  00007ff314432a40(0000) GS:ffff8b5e53600000(0000) knlGS:0000000000000000
[  129.028391] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  129.028392] CR2: 0000564dbd755970 CR3: 00000002f45d8000 CR4: 00000000003406f0
[  129.028393] Call Trace:
[  129.028429]  optc1_lock+0xa2/0xb0 [amdgpu]
[  129.028463]  dcn10_apply_ctx_for_surface+0xed/0x510 [amdgpu]
[  129.028494]  dc_commit_state+0x266/0x5d0 [amdgpu]
[  129.028523]  ? set_freesync_on_streams.part.5+0xa6/0x2a0 [amdgpu]
[  129.028552]  ? mod_freesync_set_user_enable+0x15f/0x1a0 [amdgpu]
[  129.028586]  amdgpu_dm_atomic_commit_tail+0x348/0xf80 [amdgpu]
[  129.028611]  ? amdgpu_bo_pin_restricted+0x1fe/0x2b0 [amdgpu]
[  129.028614]  ? _cond_resched+0x1a/0x50
[  129.028617]  ? wait_for_completion_timeout+0x3a/0x140
[  129.028619]  ? _cond_resched+0x1a/0x50
[  129.028621]  ? wait_for_completion_interruptible+0x37/0x180
[  129.028622]  ? ww_mutex_unlock+0x26/0x30
[  129.028630]  commit_tail+0x42/0x70 [drm_kms_helper]
[  129.028636]  drm_atomic_helper_commit+0x10c/0x120 [drm_kms_helper]
[  129.028669]  amdgpu_dm_atomic_commit+0x87/0xa0 [amdgpu]
[  129.028681]  drm_atomic_commit+0x51/0x60 [drm]
[  129.028686]  drm_atomic_helper_set_config+0x6e/0x90 [drm_kms_helper]
[  129.028695]  __drm_mode_set_config_internal+0x6b/0x120 [drm]
[  129.028704]  drm_mode_setcrtc+0x4f1/0x680 [drm]
[  129.028713]  ? drm_mode_getcrtc+0x190/0x190 [drm]
[  129.028721]  drm_ioctl_kernel+0x6b/0xb0 [drm]
[  129.028729]  drm_ioctl+0x33c/0x3f0 [drm]
[  129.028737]  ? drm_mode_getcrtc+0x190/0x190 [drm]
[  129.028760]  amdgpu_drm_ioctl+0x4f/0x90 [amdgpu]
[  129.028763]  do_vfs_ioctl+0xa6/0x610
[  129.028766]  ? recalc_sigpending+0x1b/0x50
[  129.028768]  ? _copy_from_user+0x36/0x70
[  129.028770]  SyS_ioctl+0x79/0x90
[  129.028772]  ? exit_to_usermode_loop+0xa7/0xd0
[  129.028774]  do_syscall_64+0x73/0x130
[  129.028777]  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
[  129.028778] RIP: 0033:0x7ff3118f1dd7
[  129.028779] RSP: 002b:00007fffaba215a8 EFLAGS: 00003246 ORIG_RAX: 0000000000000010
[  129.028781] RAX: ffffffffffffffda RBX: 000000000000000e RCX: 00007ff3118f1dd7
[  129.028782] RDX: 00007fffaba215e0 RSI: 00000000c06864a2 RDI: 000000000000000e
[  129.028783] RBP: 00007fffaba215e0 R08: 0000000000000000 R09: 000056528d76ac40
[  129.028784] R10: 00007fffaba21780 R11: 0000000000003246 R12: 00000000c06864a2
[  129.028785] R13: 000000000000000e R14: 000056528d25d9e0 R15: 000056528d129380
[  129.028787] Code: 44 8b 45 10 44 89 e1 48 c7 c2 00 74 e0 c0 48 c7 c7 b3 f0 e0 c0 44 89 55 d4 50 e8 91 cf c0 ff 41 83 7d 20 01 44 8b 55 d4 58 74 02 <0f> 0b 48 8d 65 d8 44 89 d0 5b 41 5c 41 5d 41 5e 41 5f 5d c3 41 
[  129.028810] ---[ end trace d73192e5e8ac0713 ]---

The kernel that I used is Linux 4.16.0.