Can't boot anymore; amdgpu fatal error

Hello everyone, sorry for my English.
My system won't boot anymore and I don't know what to do.
This is my setup: Manjaro KDE dual booting with Elementary OS in another physical disk. Everything worked well until yesterday when I could shut my system down without any problem or error.

This morning I was going to use Manjaro as always but all I could see was, and currently is, a totally black screen: no errors, no screen flashes, no text at all, no blinking cursor, no input and no output, nothing with the CTRL + ALT + F1/F2/F3...etc shortcuts.
Elementary OS, however, still works fine so it isn't an hardware failure.

I followed a guide to chroot into Manjaro from Elementary OS and I could perform a system update and some checks; nothing changed even after reinstalling the video drivers, but I got a log:

-- Logs begin at Wed 2018-12-19 21:11:22 CET, end at Sun 2018-12-23 13:20:57 CET. --
dic 23 12:12:41 riccardo-pc kernel: mc: Failed to load firmware "amdgpu/polaris11_k_mc.bin"
dic 23 12:12:41 riccardo-pc kernel: [drm:gmc_v8_0_sw_init [amdgpu]] *ERROR* Failed to load mc firmware!
dic 23 12:12:41 riccardo-pc kernel: [drm:amdgpu_device_init.cold.14 [amdgpu]] *ERROR* sw_init of IP block <gmc_v8_0> f>
dic 23 12:12:41 riccardo-pc kernel: amdgpu 0000:01:00.0: amdgpu_device_ip_init failed
dic 23 12:12:41 riccardo-pc kernel: amdgpu 0000:01:00.0: Fatal error during GPU init
dic 23 12:12:42 riccardo-pc sddm[470]: Failed to read display number from pipe
dic 23 12:12:42 riccardo-pc sddm[470]: Display server failed to start. Exiting
dic 23 12:12:42 riccardo-pc systemd-coredump[620]: Process 470 (sddm) of user 0 dumped core.
                                                   
                                                   Stack trace of thread 470:
                                                   #0  0x00007faaf725ad7f raise (libc.so.6)
                                                   #1  0x00007faaf7245672 abort (libc.so.6)
                                                   #2  0x00007faaf76127fc _ZNK14QMessageLogger5fatalEPKcz (libQt5Core.>
                                                   #3  0x000055d58b59c1f3 n/a (sddm)
                                                   #4  0x000055d58b5dbc2e _ZN4SDDM4Seat13createDisplayEi (sddm)
                                                   #5  0x000055d58b5dbe72 _ZN4SDDM4SeatC2ERK7QStringP7QObject (sddm)
                                                   #6  0x000055d58b5dde41 _ZN4SDDM11SeatManager10createSeatERK7QString>
                                                   #7  0x000055d58b5dec62 n/a (sddm)
                                                   #8  0x00007faaf782dbd0 _ZN11QMetaObject8activateEP7QObjectiiPPv (li>
                                                   #9  0x000055d58b5dceb0 _ZN4SDDM10LogindSeat19canGraphicalChangedEb >
                                                   #10 0x000055d58b5dd1c3 n/a (sddm)
                                                   #11 0x00007faaf782dbd0 _ZN11QMetaObject8activateEP7QObjectiiPPv (li>
                                                   #12 0x00007faaf8139900 _ZN23QDBusPendingCallWatcher8finishedEPS_ (l>
                                                   #13 0x00007faaf8139a01 n/a (libQt5DBus.so.5)
                                                   #14 0x00007faaf782e352 _ZN7QObject5eventEP6QEvent (libQt5Core.so.5)
                                                   #15 0x00007faaf7803c17 _ZN16QCoreApplication15notifyInternal2EP7QOb>
                                                   #16 0x00007faaf7806ccc _ZN23QCoreApplicationPrivate16sendPostedEven>
                                                   #17 0x00007faaf78579d4 n/a (libQt5Core.so.5)
                                                   #18 0x00007faaf61433cf g_main_context_dispatch (libglib-2.0.so.0)
                                                   #19 0x00007faaf6144f89 n/a (libglib-2.0.so.0)
                                                   #20 0x00007faaf6144fce g_main_context_iteration (libglib-2.0.so.0)
                                                   #21 0x00007faaf7856fc9 _ZN20QEventDispatcherGlib13processEventsE6QF>
                                                   #22 0x00007faaf78028cc _ZN10QEventLoop4execE6QFlagsINS_17ProcessEve>
                                                   #23 0x00007faaf780abc6 _ZN16QCoreApplication4execEv (libQt5Core.so.>
                                                   #24 0x000055d58b59fb0a main (sddm)
                                                   #25 0x00007faaf7247223 __libc_start_main (libc.so.6)
                                                   #26 0x000055d58b59fe0a _start (sddm)
                                                   
                                                   Stack trace of thread 495:
                                                   #0  0x00007faaf7313c21 __poll (libc.so.6)
                                                   #1  0x00007faaf6144ee0 n/a (libglib-2.0.so.0)
                                                   #2  0x00007faaf6144fce g_main_context_iteration (libglib-2.0.so.0)
                                                   #3  0x00007faaf7856fc9 _ZN20QEventDispatcherGlib13processEventsE6QF>
                                                   #4  0x00007faaf78028cc _ZN10QEventLoop4execE6QFlagsINS_17ProcessEve>
                                                   #5  0x00007faaf764beb9 _ZN7QThread4execEv (libQt5Core.so.5)
                                                   #6  0x00007faaf80ddba6 n/a (libQt5DBus.so.5)
                                                   #7  0x00007faaf7655f65 n/a (libQt5Core.so.5)
                                                   #8  0x00007faaf7209a9d start_thread (libpthread.so.0)
                                                   #9  0x00007faaf731eb23 __clone (libc.so.6)
dic 23 12:12:42 riccardo-pc sddm[630]: Failed to read display number from pipe
dic 23 12:12:42 riccardo-pc sddm[630]: Display server failed to start. Exiting
dic 23 12:12:43 riccardo-pc systemd-coredump[638]: Process 630 (sddm) of user 0 dumped core.
                                                   
                                                   Stack trace of thread 630:
                                                   #0  0x00007fd0458a3d7f raise (libc.so.6)
                                                   #1  0x00007fd04588e672 abort (libc.so.6)
                                                   #2  0x00007fd045c5b7fc _ZNK14QMessageLogger5fatalEPKcz (libQt5Core.>
                                                   #3  0x0000555562bea1f3 n/a (sddm)
                                                   #4  0x0000555562c29c2e _ZN4SDDM4Seat13createDisplayEi (sddm)
                                                   #5  0x0000555562c29e72 _ZN4SDDM4SeatC2ERK7QStringP7QObject (sddm)
                                                   #6  0x0000555562c2be41 _ZN4SDDM11SeatManager10createSeatERK7QString>
                                                   #7  0x0000555562c2cc62 n/a (sddm)
                                                   #8  0x00007fd045e76bd0 _ZN11QMetaObject8activateEP7QObjectiiPPv (li>
                                                   #9  0x0000555562c2aeb0 _ZN4SDDM10LogindSeat19canGraphicalChangedEb >
                                                   #10 0x0000555562c2b1c3 n/a (sddm)
                                                   #11 0x00007fd045e76bd0 _ZN11QMetaObject8activateEP7QObjectiiPPv (li>
                                                   #12 0x00007fd046782900 _ZN23QDBusPendingCallWatcher8finishedEPS_ (l>
                                                   #13 0x00007fd046782a01 n/a (libQt5DBus.so.5)
                                                   #14 0x00007fd045e77352 _ZN7QObject5eventEP6QEvent (libQt5Core.so.5)
                                                   #15 0x00007fd045e4cc17 _ZN16QCoreApplication15notifyInternal2EP7QOb>
                                                   #16 0x00007fd045e4fccc _ZN23QCoreApplicationPrivate16sendPostedEven>
                                                   #17 0x00007fd045ea09d4 n/a (libQt5Core.so.5)
                                                   #18 0x00007fd04478c3cf g_main_context_dispatch (libglib-2.0.so.0)
                                                   #19 0x00007fd04478df89 n/a (libglib-2.0.so.0)
                                                   #20 0x00007fd04478dfce g_main_context_iteration (libglib-2.0.so.0)
                                                   #21 0x00007fd045e9ffc9 _ZN20QEventDispatcherGlib13processEventsE6QF>
                                                   #22 0x00007fd045e4b8cc _ZN10QEventLoop4execE6QFlagsINS_17ProcessEve>
                                                   #23 0x00007fd045e53bc6 _ZN16QCoreApplication4execEv (libQt5Core.so.>
                                                   #24 0x0000555562bedb0a main (sddm)
                                                   #25 0x00007fd045890223 __libc_start_main (libc.so.6)
                                                   #26 0x0000555562bede0a _start (sddm)
                                                   
                                                   Stack trace of thread 631:
                                                   #0  0x00007fd04595cc21 __poll (libc.so.6)
                                                   #1  0x00007fd04478dee0 n/a (libglib-2.0.so.0)
                                                   #2  0x00007fd04478dfce g_main_context_iteration (libglib-2.0.so.0)
                                                   #3  0x00007fd045e9ffc9 _ZN20QEventDispatcherGlib13processEventsE6QF>
                                                   #4  0x00007fd045e4b8cc _ZN10QEventLoop4execE6QFlagsINS_17ProcessEve>
                                                   #5  0x00007fd045c94eb9 _ZN7QThread4execEv (libQt5Core.so.5)
                                                   #6  0x00007fd046726ba6 n/a (libQt5DBus.so.5)
                                                   #7  0x00007fd045c9ef65 n/a (libQt5Core.so.5)
                                                   #8  0x00007fd045852a9d start_thread (libpthread.so.0)
                                                   #9  0x00007fd045967b23 __clone (libc.so.6)
dic 23 12:12:43 riccardo-pc sddm[644]: Failed to read display number from pipe
dic 23 12:12:43 riccardo-pc sddm[644]: Display server failed to start. Exiting
dic 23 12:12:43 riccardo-pc systemd-coredump[652]: Process 644 (sddm) of user 0 dumped core.
                                                   
                                                   Stack trace of thread 644:
                                                   #0  0x00007f04d05b1d7f raise (libc.so.6)
                                                   #1  0x00007f04d059c672 abort (libc.so.6)
                                                   #2  0x00007f04d09697fc _ZNK14QMessageLogger5fatalEPKcz (libQt5Core.>
                                                   #3  0x000055d0619951f3 n/a (sddm)
                                                   #4  0x000055d0619d4c2e _ZN4SDDM4Seat13createDisplayEi (sddm)
                                                   #5  0x000055d0619d4e72 _ZN4SDDM4SeatC2ERK7QStringP7QObject (sddm)
                                                   #6  0x000055d0619d6e41 _ZN4SDDM11SeatManager10createSeatERK7QString>
                                                   #7  0x000055d0619d7c62 n/a (sddm)
                                                   #8  0x00007f04d0b84bd0 _ZN11QMetaObject8activateEP7QObjectiiPPv (li>
                                                   #9  0x000055d0619d5eb0 _ZN4SDDM10LogindSeat19canGraphicalChangedEb >
                                                   #10 0x000055d0619d61c3 n/a (sddm)
                                                   #11 0x00007f04d0b84bd0 _ZN11QMetaObject8activateEP7QObjectiiPPv (li>
                                                   #12 0x00007f04d1490900 _ZN23QDBusPendingCallWatcher8finishedEPS_ (l>
                                                   #13 0x00007f04d1490a01 n/a (libQt5DBus.so.5)
                                                   #14 0x00007f04d0b85352 _ZN7QObject5eventEP6QEvent (libQt5Core.so.5)
                                                   #15 0x00007f04d0b5ac17 _ZN16QCoreApplication15notifyInternal2EP7QOb>
                                                   #16 0x00007f04d0b5dccc _ZN23QCoreApplicationPrivate16sendPostedEven>
                                                   #17 0x00007f04d0bae9d4 n/a (libQt5Core.so.5)
                                                   #18 0x00007f04cf49a3cf g_main_context_dispatch (libglib-2.0.so.0)
                                                   #19 0x00007f04cf49bf89 n/a (libglib-2.0.so.0)
                                                   #20 0x00007f04cf49bfce g_main_context_iteration (libglib-2.0.so.0)
                                                   #21 0x00007f04d0badfc9 _ZN20QEventDispatcherGlib13processEventsE6QF>
                                                   #22 0x00007f04d0b598cc _ZN10QEventLoop4execE6QFlagsINS_17ProcessEve>
                                                   #23 0x00007f04d0b61bc6 _ZN16QCoreApplication4execEv (libQt5Core.so.>
                                                   #24 0x000055d061998b0a main (sddm)
                                                   #25 0x00007f04d059e223 __libc_start_main (libc.so.6)
                                                   #26 0x000055d061998e0a _start (sddm)
                                                   
                                                   Stack trace of thread 645:
                                                   #0  0x00007f04d066ac21 __poll (libc.so.6)
                                                   #1  0x00007f04cf49bee0 n/a (libglib-2.0.so.0)
                                                   #2  0x00007f04cf49bfce g_main_context_iteration (libglib-2.0.so.0)
                                                   #3  0x00007f04d0badfc9 _ZN20QEventDispatcherGlib13processEventsE6QF>
                                                   #4  0x00007f04d0b598cc _ZN10QEventLoop4execE6QFlagsINS_17ProcessEve>
                                                   #5  0x00007f04d09a2eb9 _ZN7QThread4execEv (libQt5Core.so.5)
                                                   #6  0x00007f04d1434ba6 n/a (libQt5DBus.so.5)
                                                   #7  0x00007f04d09acf65 n/a (libQt5Core.so.5)
                                                   #8  0x00007f04d0560a9d start_thread (libpthread.so.0)
                                                   #9  0x00007f04d0675b23 __clone (libc.so.6)
dic 23 12:12:43 riccardo-pc sddm[658]: Failed to read display number from pipe
dic 23 12:12:43 riccardo-pc sddm[658]: Display server failed to start. Exiting
dic 23 12:12:44 riccardo-pc systemd-coredump[667]: Process 658 (sddm) of user 0 dumped core.
                                                   
                                                   Stack trace of thread 658:
                                                   #0  0x00007fc842105d7f raise (libc.so.6)
                                                   #1  0x00007fc8420f0672 abort (libc.so.6)
                                                   #2  0x00007fc8424bd7fc _ZNK14QMessageLogger5fatalEPKcz (libQt5Core.>
                                                   #3  0x00005630b6d071f3 n/a (sddm)
                                                   #4  0x00005630b6d46c2e _ZN4SDDM4Seat13createDisplayEi (sddm)
                                                   #5  0x00005630b6d46e72 _ZN4SDDM4SeatC2ERK7QStringP7QObject (sddm)
                                                   #6  0x00005630b6d48e41 _ZN4SDDM11SeatManager10createSeatERK7QString>
                                                   #7  0x00005630b6d49c62 n/a (sddm)
                                                   #8  0x00007fc8426d8bd0 _ZN11QMetaObject8activateEP7QObjectiiPPv (li>
                                                   #9  0x00005630b6d47eb0 _ZN4SDDM10LogindSeat19canGraphicalChangedEb >
                                                   #10 0x00005630b6d481c3 n/a (sddm)
                                                   #11 0x00007fc8426d8bd0 _ZN11QMetaObject8activateEP7QObjectiiPPv (li>
                                                   #12 0x00007fc842fe4900 _ZN23QDBusPendingCallWatcher8finishedEPS_ (l>
                                                   #13 0x00007fc842fe4a01 n/a (libQt5DBus.so.5)
                                                   #14 0x00007fc8426d9352 _ZN7QObject5eventEP6QEvent (libQt5Core.so.5)
                                                   #15 0x00007fc8426aec17 _ZN16QCoreApplication15notifyInternal2EP7QOb>
                                                   #16 0x00007fc8426b1ccc _ZN23QCoreApplicationPrivate16sendPostedEven>
                                                   #17 0x00007fc8427029d4 n/a (libQt5Core.so.5)
                                                   #18 0x00007fc840fee3cf g_main_context_dispatch (libglib-2.0.so.0)
                                                   #19 0x00007fc840feff89 n/a (libglib-2.0.so.0)
                                                   #20 0x00007fc840feffce g_main_context_iteration (libglib-2.0.so.0)
                                                   #21 0x00007fc842701fc9 _ZN20QEventDispatcherGlib13processEventsE6QF>
                                                   #22 0x00007fc8426ad8cc _ZN10QEventLoop4execE6QFlagsINS_17ProcessEve>
                                                   #23 0x00007fc8426b5bc6 _ZN16QCoreApplication4execEv (libQt5Core.so.>
                                                   #24 0x00005630b6d0ab0a main (sddm)
                                                   #25 0x00007fc8420f2223 __libc_start_main (libc.so.6)
                                                   #26 0x00005630b6d0ae0a _start (sddm)
                                                   
                                                   Stack trace of thread 659:
                                                   #0  0x00007fc8421bec21 __poll (libc.so.6)
                                                   #1  0x00007fc840fefee0 n/a (libglib-2.0.so.0)
                                                   #2  0x00007fc840feffce g_main_context_iteration (libglib-2.0.so.0)
                                                   #3  0x00007fc842701fc9 _ZN20QEventDispatcherGlib13processEventsE6QF>
                                                   #4  0x00007fc8426ad8cc _ZN10QEventLoop4execE6QFlagsINS_17ProcessEve>
                                                   #5  0x00007fc8424f6eb9 _ZN7QThread4execEv (libQt5Core.so.5)
                                                   #6  0x00007fc842f88ba6 n/a (libQt5DBus.so.5)
                                                   #7  0x00007fc842500f65 n/a (libQt5Core.so.5)
                                                   #8  0x00007fc8420b4a9d start_thread (libpthread.so.0)
                                                   #9  0x00007fc8421c9b23 __clone (libc.so.6)
dic 23 12:12:44 riccardo-pc sddm[673]: Failed to read display number from pipe
dic 23 12:12:44 riccardo-pc sddm[673]: Display server failed to start. Exiting
dic 23 12:12:44 riccardo-pc systemd-coredump[682]: Process 673 (sddm) of user 0 dumped core.
                                                   
                                                   Stack trace of thread 673:
                                                   #0  0x00007fa785ab4d7f raise (libc.so.6)
                                                   #1  0x00007fa785a9f672 abort (libc.so.6)
                                                   #2  0x00007fa785e6c7fc _ZNK14QMessageLogger5fatalEPKcz (libQt5Core.>
                                                   #3  0x000055d120b5a1f3 n/a (sddm)
                                                   #4  0x000055d120b99c2e _ZN4SDDM4Seat13createDisplayEi (sddm)
                                                   #5  0x000055d120b99e72 _ZN4SDDM4SeatC2ERK7QStringP7QObject (sddm)
                                                   #6  0x000055d120b9be41 _ZN4SDDM11SeatManager10createSeatERK7QString>
                                                   #7  0x000055d120b9cc62 n/a (sddm)
                                                   #8  0x00007fa786087bd0 _ZN11QMetaObject8activateEP7QObjectiiPPv (li>
                                                   #9  0x000055d120b9aeb0 _ZN4SDDM10LogindSeat19canGraphicalChangedEb >
                                                   #10 0x000055d120b9b1c3 n/a (sddm)
                                                   #11 0x00007fa786087bd0 _ZN11QMetaObject8activateEP7QObjectiiPPv (li>
                                                   #12 0x00007fa786993900 _ZN23QDBusPendingCallWatcher8finishedEPS_ (l>
                                                   #13 0x00007fa786993a01 n/a (libQt5DBus.so.5)
                                                   #14 0x00007fa786088352 _ZN7QObject5eventEP6QEvent (libQt5Core.so.5)
                                                   #15 0x00007fa78605dc17 _ZN16QCoreApplication15notifyInternal2EP7QOb>
                                                   #16 0x00007fa786060ccc _ZN23QCoreApplicationPrivate16sendPostedEven>
                                                   #17 0x00007fa7860b19d4 n/a (libQt5Core.so.5)
                                                   #18 0x00007fa78499d3cf g_main_context_dispatch (libglib-2.0.so.0)
                                                   #19 0x00007fa78499ef89 n/a (libglib-2.0.so.0)
                                                   #20 0x00007fa78499efce g_main_context_iteration (libglib-2.0.so.0)
                                                   #21 0x00007fa7860b0fc9 _ZN20QEventDispatcherGlib13processEventsE6QF>
                                                   #22 0x00007fa78605c8cc _ZN10QEventLoop4execE6QFlagsINS_17ProcessEve>
                                                   #23 0x00007fa786064bc6 _ZN16QCoreApplication4execEv (libQt5Core.so.>
                                                   #24 0x000055d120b5db0a main (sddm)
                                                   #25 0x00007fa785aa1223 __libc_start_main (libc.so.6)
                                                   #26 0x000055d120b5de0a _start (sddm)
                                                   
                                                   Stack trace of thread 674:
                                                   #0  0x00007fa785b6dc21 __poll (libc.so.6)
                                                   #1  0x00007fa78499eee0 n/a (libglib-2.0.so.0)
                                                   #2  0x00007fa78499efce g_main_context_iteration (libglib-2.0.so.0)
                                                   #3  0x00007fa7860b0fc9 _ZN20QEventDispatcherGlib13processEventsE6QF>
                                                   #4  0x00007fa78605c8cc _ZN10QEventLoop4execE6QFlagsINS_17ProcessEve>
                                                   #5  0x00007fa785ea5eb9 _ZN7QThread4execEv (libQt5Core.so.5)
                                                   #6  0x00007fa786937ba6 n/a (libQt5DBus.so.5)
                                                   #7  0x00007fa785eaff65 n/a (libQt5Core.so.5)
                                                   #8  0x00007fa785a63a9d start_thread (libpthread.so.0)
                                                   #9  0x00007fa785b78b23 __clone (libc.so.6)
dic 23 12:12:44 riccardo-pc systemd[1]: Failed to start Simple Desktop Display Manager.

The kernel was 4.19 before and still is 4.19 now, it is also the only installed version. I can't really find anything that changed at all. No sign of updates etc.

This is the response from sudo pacman -Syyu

:: Sincronizzazione dei database in corso...
 core                                          147,3 KiB   115K/s 00:01 [########################################] 100%
 extra                                        1852,2 KiB   304K/s 00:06 [########################################] 100%
 community                                       5,1 MiB   477K/s 00:11 [########################################] 100%
 multilib                                      184,7 KiB   825K/s 00:00 [########################################] 100%
:: Aggiornamento del sistema in corso...
attenzione: chromium: la versione installata (71.0.3578.98-0) è più recente di quella presente in extra (71.0.3578.80-1)
attenzione: snapd: la versione installata (2.36.3-1) è più recente di quella presente in community (2.35.5-2)
 non ci sono aggiornamenti disponibili

So I can't find anything worth noting.
What could I do? Thanks

EDIT: More info

[manjaro /]# inxi -Fxxxz
12System:    12Host manjaro 12Kernel 4.19.0-3-MANJARO x86_64 12bits 64 12compiler gcc 12v 8.2.1 12Console N/A 
           12wm kwin_x11 12dm N/A 12Distro Manjaro Linux 
12Machine:   12Type Desktop 12Mobo ASRock 12model Z77 Pro4 12serial N/A 12BIOS American Megatrends 12v P1.50 
           12date 09/04/2012 

(upower:7690): UPower-WARNING **: 16:42:46.709: Cannot connect to upowerd: Could not connect: No such file or directory
12Battery:   12Device-1 hidpp_battery_0 12model Logitech M705 12serial <filter> 12charge N/A 
           12status Discharging 
12CPU:       12Topology Quad Core 12model Intel Core i5-3450 12bits 64 12type MCP 12arch Ivy Bridge 12rev 9 
           12L1 cache 256 KiB 12L2 cache 6144 KiB 12L3 cache 6144 KiB 
           12flags lm nx pae sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx 12bogomips 24808 
           12Speed 1600 MHz 12min/max 1600/3500 MHz 12Core speeds (MHz) 121 1600 122 1600 123 1601 124 1600 
12Graphics:  12Device-1 Intel Xeon E3-1200 v2/3rd Gen Core processor Graphics 12vendor ASRock 
           12driver i915 12v kernel 12bus ID 00:02.0 12chip ID 8086:0152 
           12Device-2 AMD Baffin [Radeon RX 550 640SP / RX 560/560X] 12vendor Gigabyte 12driver amdgpu 
           12v kernel 12bus ID 01:00.0 12chip ID 1002:67ff 
           12Display 12server X.org 1.20.3 12driver ati,intel,radeon 12unloaded modesetting 
           12alternate fbdev,vesa 12compositor kwin_x11 12tty N/A 
           12Message Advanced graphics data unavailable for root. 
12Audio:     12Device-1 Intel 7 Series/C216 Family High Definition Audio 12vendor ASRock 
           12driver snd_hda_intel 12v kernel 12bus ID 00:1b.0 12chip ID 8086:1e20 
           12Device-2 AMD 12vendor Gigabyte 12driver snd_hda_intel 12v kernel 12bus ID 01:00.1 
           12chip ID 1002:aae0 
           12Sound Server ALSA 12v k4.19.0-3-MANJARO 
12Network:   12Device-1 Realtek RTL8111/8168/8411 PCI Express Gigabit Ethernet 12vendor ASRock 
           12driver r8169 12v kernel 12port d000 12bus ID 04:00.0 12chip ID 10ec:8168 
           12IF enp4s0 12state down 12mac <filter> 
           12Device-2 Samsung GT-I9500 [Galaxy S4] / GT-I9250 [Galaxy Nexus] (network tethering) 
           12type USB 12driver rndis_host 12bus ID 2-1:4 12chip ID 04e8:6863 12serial <filter> 
           12IF enp0s20u1 12state unknown 12speed N/A 12duplex N/A 12mac <filter> 
           12Device-3 Realtek RTL8812AU 802.11a/b/g/n/ac 2T2R DB WLAN Adapter 12type USB 
           12driver usb-network 12bus ID 2-3:2 12chip ID 0bda:8812 12serial <filter> 
12Drives:    12Local Storage 12total 1.20 TiB 12used 29.93 GiB (2.4%) 
           12ID-1 /dev/sda 12vendor Hitachi 12model HDS721616PLA380 12size 153.39 GiB 12speed 3.0 Gb/s 
           12serial <filter> 12rev AB3A 
           12ID-2 /dev/sdb 12vendor Seagate 12model ST1000DM003-1CH162 12size 931.51 GiB 12speed 6.0 Gb/s 
           12serial <filter> 12rev CC44 
           12ID-3 /dev/sdc 12vendor Crucial 12model M4-CT128M4SSD2 12size 119.24 GiB 12speed 6.0 Gb/s 
           12serial <filter> 12rev 070H 
           12ID-4 /dev/sdd 12type USB 12vendor Kingston 12model DataTraveler 3.0 12size 28.91 GiB 
           12serial <filter> 12rev PMAP 
12Partition: 12ID-1 / 12size 108.21 GiB 12used 29.76 GiB (27.5%) 12fs ext4 12dev /dev/sdc1 
12Sensors:   12System Temperatures 12cpu 36.0 C 12mobo N/A 12gpu amdgpu 12temp 34 C 
           12Fan Speeds (RPM) N/A 12gpu amdgpu 12fan 1527 
12Info:      12Processes 203 12Uptime 20m 12Memory 7.68 GiB 12used 1.29 GiB (16.8%) 12Init systemd 12v 239 
           12Compilers 12gcc 8.2.1 12Client Unknown Client: systemd 12inxi 3.0.28

This is a dmesg for pci

[manjaro /]# inxi -Fxxxz
12System:    12Host manjaro 12Kernel 4.19.0-3-MANJARO x86_64 12bits 64 12compiler gcc 12v 8.2.1 12Console N/A 
           12wm kwin_x11 12dm N/A 12Distro Manjaro Linux 
12Machine:   12Type Desktop 12Mobo ASRock 12model Z77 Pro4 12serial N/A 12BIOS American Megatrends 12v P1.50 
           12date 09/04/2012 

(upower:7690): UPower-WARNING **: 16:42:46.709: Cannot connect to upowerd: Could not connect: No such file or directory
12Battery:   12Device-1 hidpp_battery_0 12model Logitech M705 12serial <filter> 12charge N/A 
           12status Discharging 
12CPU:       12Topology Quad Core 12model Intel Core i5-3450 12bits 64 12type MCP 12arch Ivy Bridge 12rev 9 
           12L1 cache 256 KiB 12L2 cache 6144 KiB 12L3 cache 6144 KiB 
           12flags lm nx pae sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx 12bogomips 24808 
           12Speed 1600 MHz 12min/max 1600/3500 MHz 12Core speeds (MHz) 121 1600 122 1600 123 1601 124 1600 
12Graphics:  12Device-1 Intel Xeon E3-1200 v2/3rd Gen Core processor Graphics 12vendor ASRock 
           12driver i915 12v kernel 12bus ID 00:02.0 12chip ID 8086:0152 
           12Device-2 AMD Baffin [Radeon RX 550 640SP / RX 560/560X] 12vendor Gigabyte 12driver amdgpu 
           12v kernel 12bus ID 01:00.0 12chip ID 1002:67ff 
           12Display 12server X.org 1.20.3 12driver ati,intel,radeon 12unloaded modesetting 
           12alternate fbdev,vesa 12compositor kwin_x11 12tty N/A 
           12Message Advanced graphics data unavailable for root. 
12Audio:     12Device-1 Intel 7 Series/C216 Family High Definition Audio 12vendor ASRock 
           12driver snd_hda_intel 12v kernel 12bus ID 00:1b.0 12chip ID 8086:1e20 
           12Device-2 AMD 12vendor Gigabyte 12driver snd_hda_intel 12v kernel 12bus ID 01:00.1 
           12chip ID 1002:aae0 
           12Sound Server ALSA 12v k4.19.0-3-MANJARO 
12Network:   12Device-1 Realtek RTL8111/8168/8411 PCI Express Gigabit Ethernet 12vendor ASRock 
           12driver r8169 12v kernel 12port d000 12bus ID 04:00.0 12chip ID 10ec:8168 
           12IF enp4s0 12state down 12mac <filter> 
           12Device-2 Samsung GT-I9500 [Galaxy S4] / GT-I9250 [Galaxy Nexus] (network tethering) 
           12type USB 12driver rndis_host 12bus ID 2-1:4 12chip ID 04e8:6863 12serial <filter> 
           12IF enp0s20u1 12state unknown 12speed N/A 12duplex N/A 12mac <filter> 
           12Device-3 Realtek RTL8812AU 802.11a/b/g/n/ac 2T2R DB WLAN Adapter 12type USB 
           12driver usb-network 12bus ID 2-3:2 12chip ID 0bda:8812 12serial <filter> 
12Drives:    12Local Storage 12total 1.20 TiB 12used 29.93 GiB (2.4%) 
           12ID-1 /dev/sda 12vendor Hitachi 12model HDS721616PLA380 12size 153.39 GiB 12speed 3.0 Gb/s 
           12serial <filter> 12rev AB3A 
           12ID-2 /dev/sdb 12vendor Seagate 12model ST1000DM003-1CH162 12size 931.51 GiB 12speed 6.0 Gb/s 
           12serial <filter> 12rev CC44 
           12ID-3 /dev/sdc 12vendor Crucial 12model M4-CT128M4SSD2 12size 119.24 GiB 12speed 6.0 Gb/s 
           12serial <filter> 12rev 070H 
           12ID-4 /dev/sdd 12type USB 12vendor Kingston 12model DataTraveler 3.0 12size 28.91 GiB 
           12serial <filter> 12rev PMAP 
12Partition: 12ID-1 / 12size 108.21 GiB 12used 29.76 GiB (27.5%) 12fs ext4 12dev /dev/sdc1 
12Sensors:   12System Temperatures 12cpu 36.0 C 12mobo N/A 12gpu amdgpu 12temp 34 C 
           12Fan Speeds (RPM) N/A 12gpu amdgpu 12fan 1527 
12Info:      12Processes 203 12Uptime 20m 12Memory 7.68 GiB 12used 1.29 GiB (16.8%) 12Init systemd 12v 239 
           12Compilers 12gcc 8.2.1 12Client Unknown Client: systemd 12inxi 3.0.28

This is for journalctl -p3 -b -1`

[manjaro /]# journalctl -p3 -b -1
-- Logs begin at Wed 2018-12-19 21:11:22 CET, end at Sun 2018-12-23 15:18:05 CET. --
Dec 23 15:12:48 riccardo-pc kernel: mc: Failed to load firmware "amdgpu/polaris11_k_mc.bin"
Dec 23 15:12:48 riccardo-pc kernel: [drm:gmc_v8_0_sw_init [amdgpu]] *ERROR* Failed to load mc firmware!
Dec 23 15:12:48 riccardo-pc kernel: [drm:amdgpu_device_init.cold.14 [amdgpu]] *ERROR* sw_init of IP block <gmc_v8_>
Dec 23 15:12:48 riccardo-pc kernel: amdgpu 0000:01:00.0: amdgpu_device_ip_init failed
Dec 23 15:12:48 riccardo-pc kernel: amdgpu 0000:01:00.0: Fatal error during GPU init
Dec 23 15:12:49 riccardo-pc sddm[478]: Failed to read display number from pipe
Dec 23 15:12:49 riccardo-pc sddm[478]: Display server failed to start. Exiting
Dec 23 15:12:49 riccardo-pc systemd-coredump[524]: Process 478 (sddm) of user 0 dumped core.
                                                   
                                                   Stack trace of thread 478:
                                                   #0  0x00007f1b35bead7f raise (libc.so.6)
                                                   #1  0x00007f1b35bd5672 abort (libc.so.6)
                                                   #2  0x00007f1b35fa27fc _ZNK14QMessageLogger5fatalEPKcz (libQt5C>
                                                   #3  0x000055feb29021f3 n/a (sddm)
                                                   #4  0x000055feb2941c2e _ZN4SDDM4Seat13createDisplayEi (sddm)
                                                   #5  0x000055feb2941e72 _ZN4SDDM4SeatC2ERK7QStringP7QObject (sdd>
                                                   #6  0x000055feb2943e41 _ZN4SDDM11SeatManager10createSeatERK7QSt>
                                                   #7  0x000055feb2944c62 n/a (sddm)
                                                   #8  0x00007f1b361bdbd0 _ZN11QMetaObject8activateEP7QObjectiiPPv>
                                                   #9  0x000055feb2942eb0 _ZN4SDDM10LogindSeat19canGraphicalChange>
                                                   #10 0x000055feb29431c3 n/a (sddm)
                                                   #11 0x00007f1b361bdbd0 _ZN11QMetaObject8activateEP7QObjectiiPPv>
                                                   #12 0x00007f1b36ac9900 _ZN23QDBusPendingCallWatcher8finishedEPS>
                                                   #13 0x00007f1b36ac9a01 n/a (libQt5DBus.so.5)
                                                   #14 0x00007f1b361be352 _ZN7QObject5eventEP6QEvent (libQt5Core.s>
                                                   #15 0x00007f1b36193c17 _ZN16QCoreApplication15notifyInternal2EP>
                                                   #16 0x00007f1b36196ccc _ZN23QCoreApplicationPrivate16sendPosted>
                                                   #17 0x00007f1b361e79d4 n/a (libQt5Core.so.5)
                                                   #18 0x00007f1b34ad33cf g_main_context_dispatch (libglib-2.0.so.>
                                                   #19 0x00007f1b34ad4f89 n/a (libglib-2.0.so.0)
                                                   #20 0x00007f1b34ad4fce g_main_context_iteration (libglib-2.0.so>
                                                   #21 0x00007f1b361e6fc9 _ZN20QEventDispatcherGlib13processEvents>
                                                   #22 0x00007f1b361928cc _ZN10QEventLoop4execE6QFlagsINS_17Proces>
                                                   #23 0x00007f1b3619abc6 _ZN16QCoreApplication4execEv (libQt5Core>
                                                   #24 0x000055feb2905b0a main (sddm)
                                                   #25 0x00007f1b35bd7223 __libc_start_main (libc.so.6)
                                                   #26 0x000055feb2905e0a _start (sddm)
                                                   
                                                   Stack trace of thread 512:
                                                   #0  0x00007f1b35ca3c21 __poll (libc.so.6)
                                                   #1  0x00007f1b34ad4ee0 n/a (libglib-2.0.so.0)
                                                   #2  0x00007f1b34ad4fce g_main_context_iteration (libglib-2.0.so>
                                                   #3  0x00007f1b361e6fc9 _ZN20QEventDispatcherGlib13processEvents>
                                                   #4  0x00007f1b361928cc _ZN10QEventLoop4execE6QFlagsINS_17Proces>
                                                   #5  0x00007f1b35fdbeb9 _ZN7QThread4execEv (libQt5Core.so.5)
                                                   #6  0x00007f1b36a6dba6 n/a (libQt5DBus.so.5)
                                                   #7  0x00007f1b35fe5f65 n/a (libQt5Core.so.5)
                                                   #8  0x00007f1b35b99a9d start_thread (libpthread.so.0)
                                                   #9  0x00007f1b35caeb23 __clone (libc.so.6)
Dec 23 15:12:50 riccardo-pc sddm[631]: Failed to read display number from pipe
Dec 23 15:12:50 riccardo-pc sddm[631]: Display server failed to start. Exiting
Dec 23 15:12:50 riccardo-pc systemd-coredump[639]: Process 631 (sddm) of user 0 dumped core.
                                                   
                                                   Stack trace of thread 631:
                                                   #0  0x00007fa6080a3d7f raise (libc.so.6)
                                                   #1  0x00007fa60808e672 abort (libc.so.6)
                                                   #2  0x00007fa60845b7fc _ZNK14QMessageLogger5fatalEPKcz (libQt5C>
                                                   #3  0x000056444c9a91f3 n/a (sddm)
                                                   #4  0x000056444c9e8c2e _ZN4SDDM4Seat13createDisplayEi (sddm)
                                                   #5  0x000056444c9e8e72 _ZN4SDDM4SeatC2ERK7QStringP7QObject (sdd>
                                                   #6  0x000056444c9eae41 _ZN4SDDM11SeatManager10createSeatERK7QSt>
                                                   #7  0x000056444c9ebc62 n/a (sddm)
                                                   #8  0x00007fa608676bd0 _ZN11QMetaObject8activateEP7QObjectiiPPv>
                                                   #9  0x000056444c9e9eb0 _ZN4SDDM10LogindSeat19canGraphicalChange>
                                                   #10 0x000056444c9ea1c3 n/a (sddm)
                                                   #11 0x00007fa608676bd0 _ZN11QMetaObject8activateEP7QObjectiiPPv>
                                                   #12 0x00007fa608f82900 _ZN23QDBusPendingCallWatcher8finishedEPS>
                                                   #13 0x00007fa608f82a01 n/a (libQt5DBus.so.5)
                                                   #14 0x00007fa608677352 _ZN7QObject5eventEP6QEvent (libQt5Core.s>
                                                   #15 0x00007fa60864cc17 _ZN16QCoreApplication15notifyInternal2EP>
                                                   #16 0x00007fa60864fccc _ZN23QCoreApplicationPrivate16sendPosted>
                                                   #17 0x00007fa6086a09d4 n/a (libQt5Core.so.5)
                                                   #18 0x00007fa606f8c3cf g_main_context_dispatch (libglib-2.0.so.>
                                                   #19 0x00007fa606f8df89 n/a (libglib-2.0.so.0)
                                                   #20 0x00007fa606f8dfce g_main_context_iteration (libglib-2.0.so>
                                                   #21 0x00007fa60869ffc9 _ZN20QEventDispatcherGlib13processEvents>
                                                   #22 0x00007fa60864b8cc _ZN10QEventLoop4execE6QFlagsINS_17Proces>
                                                   #23 0x00007fa608653bc6 _ZN16QCoreApplication4execEv (libQt5Core>
                                                   #24 0x000056444c9acb0a main (sddm)
                                                   #25 0x00007fa608090223 __libc_start_main (libc.so.6)
                                                   #26 0x000056444c9ace0a _start (sddm)
                                                   
                                                   Stack trace of thread 632:
                                                   #0  0x00007fa60815cc21 __poll (libc.so.6)
                                                   #1  0x00007fa606f8dee0 n/a (libglib-2.0.so.0)
                                                   #2  0x00007fa606f8dfce g_main_context_iteration (libglib-2.0.so>
                                                   #3  0x00007fa60869ffc9 _ZN20QEventDispatcherGlib13processEvents>
                                                   #4  0x00007fa60864b8cc _ZN10QEventLoop4execE6QFlagsINS_17Proces>
                                                   #5  0x00007fa608494eb9 _ZN7QThread4execEv (libQt5Core.so.5)
                                                   #6  0x00007fa608f26ba6 n/a (libQt5DBus.so.5)
                                                   #7  0x00007fa60849ef65 n/a (libQt5Core.so.5)
                                                   #8  0x00007fa608052a9d start_thread (libpthread.so.0)
                                                   #9  0x00007fa608167b23 __clone (libc.so.6)
Dec 23 15:12:50 riccardo-pc sddm[645]: Failed to read display number from pipe
Dec 23 15:12:50 riccardo-pc sddm[645]: Display server failed to start. Exiting
Dec 23 15:12:50 riccardo-pc systemd-coredump[654]: Process 645 (sddm) of user 0 dumped core.
                                                   
                                                   Stack trace of thread 645:
                                                   #0  0x00007f683dcaed7f raise (libc.so.6)
                                                   #1  0x00007f683dc99672 abort (libc.so.6)
                                                   #2  0x00007f683e0667fc _ZNK14QMessageLogger5fatalEPKcz (libQt5C>
                                                   #3  0x000055cb1a9d61f3 n/a (sddm)
                                                   #4  0x000055cb1aa15c2e _ZN4SDDM4Seat13createDisplayEi (sddm)
                                                   #5  0x000055cb1aa15e72 _ZN4SDDM4SeatC2ERK7QStringP7QObject (sdd>
                                                   #6  0x000055cb1aa17e41 _ZN4SDDM11SeatManager10createSeatERK7QSt>
                                                   #7  0x000055cb1aa18c62 n/a (sddm)
                                                   #8  0x00007f683e281bd0 _ZN11QMetaObject8activateEP7QObjectiiPPv>
                                                   #9  0x000055cb1aa16eb0 _ZN4SDDM10LogindSeat19canGraphicalChange>
                                                   #10 0x000055cb1aa171c3 n/a (sddm)
                                                   #11 0x00007f683e281bd0 _ZN11QMetaObject8activateEP7QObjectiiPPv>
                                                   #12 0x00007f683eb8d900 _ZN23QDBusPendingCallWatcher8finishedEPS>
                                                   #13 0x00007f683eb8da01 n/a (libQt5DBus.so.5)
                                                   #14 0x00007f683e282352 _ZN7QObject5eventEP6QEvent (libQt5Core.s>
                                                   #15 0x00007f683e257c17 _ZN16QCoreApplication15notifyInternal2EP>
                                                   #16 0x00007f683e25accc _ZN23QCoreApplicationPrivate16sendPosted>
                                                   #17 0x00007f683e2ab9d4 n/a (libQt5Core.so.5)
                                                   #18 0x00007f683cb973cf g_main_context_dispatch (libglib-2.0.so.>
                                                   #19 0x00007f683cb98f89 n/a (libglib-2.0.so.0)
                                                   #20 0x00007f683cb98fce g_main_context_iteration (libglib-2.0.so>
                                                   #21 0x00007f683e2aafc9 _ZN20QEventDispatcherGlib13processEvents>
                                                   #22 0x00007f683e2568cc _ZN10QEventLoop4execE6QFlagsINS_17Proces>
                                                   #23 0x00007f683e25ebc6 _ZN16QCoreApplication4execEv (libQt5Core>
                                                   #24 0x000055cb1a9d9b0a main (sddm)
                                                   #25 0x00007f683dc9b223 __libc_start_main (libc.so.6)
                                                   #26 0x000055cb1a9d9e0a _start (sddm)
                                                   
                                                   Stack trace of thread 646:
                                                   #0  0x00007f683dd67c21 __poll (libc.so.6)
                                                   #1  0x00007f683cb98ee0 n/a (libglib-2.0.so.0)
                                                   #2  0x00007f683cb98fce g_main_context_iteration (libglib-2.0.so>
                                                   #3  0x00007f683e2aafc9 _ZN20QEventDispatcherGlib13processEvents>
                                                   #4  0x00007f683e2568cc _ZN10QEventLoop4execE6QFlagsINS_17Proces>
                                                   #5  0x00007f683e09feb9 _ZN7QThread4execEv (libQt5Core.so.5)
                                                   #6  0x00007f683eb31ba6 n/a (libQt5DBus.so.5)
                                                   #7  0x00007f683e0a9f65 n/a (libQt5Core.so.5)
                                                   #8  0x00007f683dc5da9d start_thread (libpthread.so.0)
                                                   #9  0x00007f683dd72b23 __clone (libc.so.6)
Dec 23 15:12:51 riccardo-pc sddm[660]: Failed to read display number from pipe
Dec 23 15:12:51 riccardo-pc sddm[660]: Display server failed to start. Exiting
Dec 23 15:12:51 riccardo-pc systemd-coredump[668]: Process 660 (sddm) of user 0 dumped core.
                                                   
                                                   Stack trace of thread 660:
                                                   #0  0x00007fde47a1ed7f raise (libc.so.6)
                                                   #1  0x00007fde47a09672 abort (libc.so.6)
                                                   #2  0x00007fde47dd67fc _ZNK14QMessageLogger5fatalEPKcz (libQt5C>
                                                   #3  0x000055e5f295f1f3 n/a (sddm)
                                                   #4  0x000055e5f299ec2e _ZN4SDDM4Seat13createDisplayEi (sddm)
                                                   #5  0x000055e5f299ee72 _ZN4SDDM4SeatC2ERK7QStringP7QObject (sdd>
                                                   #6  0x000055e5f29a0e41 _ZN4SDDM11SeatManager10createSeatERK7QSt>
                                                   #7  0x000055e5f29a1c62 n/a (sddm)
                                                   #8  0x00007fde47ff1bd0 _ZN11QMetaObject8activateEP7QObjectiiPPv>
                                                   #9  0x000055e5f299feb0 _ZN4SDDM10LogindSeat19canGraphicalChange>
                                                   #10 0x000055e5f29a01c3 n/a (sddm)
                                                   #11 0x00007fde47ff1bd0 _ZN11QMetaObject8activateEP7QObjectiiPPv>
                                                   #12 0x00007fde488fd900 _ZN23QDBusPendingCallWatcher8finishedEPS>
                                                   #13 0x00007fde488fda01 n/a (libQt5DBus.so.5)
                                                   #14 0x00007fde47ff2352 _ZN7QObject5eventEP6QEvent (libQt5Core.s>
                                                   #15 0x00007fde47fc7c17 _ZN16QCoreApplication15notifyInternal2EP>
                                                   #16 0x00007fde47fcaccc _ZN23QCoreApplicationPrivate16sendPosted>
                                                   #17 0x00007fde4801b9d4 n/a (libQt5Core.so.5)
                                                   #18 0x00007fde469073cf g_main_context_dispatch (libglib-2.0.so.>
                                                   #19 0x00007fde46908f89 n/a (libglib-2.0.so.0)
                                                   #20 0x00007fde46908fce g_main_context_iteration (libglib-2.0.so>
                                                   #21 0x00007fde4801afc9 _ZN20QEventDispatcherGlib13processEvents>
                                                   #22 0x00007fde47fc68cc _ZN10QEventLoop4execE6QFlagsINS_17Proces>
                                                   #23 0x00007fde47fcebc6 _ZN16QCoreApplication4execEv (libQt5Core>
                                                   #24 0x000055e5f2962b0a main (sddm)
                                                   #25 0x00007fde47a0b223 __libc_start_main (libc.so.6)
                                                   #26 0x000055e5f2962e0a _start (sddm)
                                                   
                                                   Stack trace of thread 661:
                                                   #0  0x00007fde47ad7c21 __poll (libc.so.6)
                                                   #1  0x00007fde46908ee0 n/a (libglib-2.0.so.0)
                                                   #2  0x00007fde46908fce g_main_context_iteration (libglib-2.0.so>
                                                   #3  0x00007fde4801afc9 _ZN20QEventDispatcherGlib13processEvents>
                                                   #4  0x00007fde47fc68cc _ZN10QEventLoop4execE6QFlagsINS_17Proces>
                                                   #5  0x00007fde47e0feb9 _ZN7QThread4execEv (libQt5Core.so.5)
                                                   #6  0x00007fde488a1ba6 n/a (libQt5DBus.so.5)
                                                   #7  0x00007fde47e19f65 n/a (libQt5Core.so.5)
                                                   #8  0x00007fde479cda9d start_thread (libpthread.so.0)
                                                   #9  0x00007fde47ae2b23 __clone (libc.so.6)
Dec 23 15:12:51 riccardo-pc sddm[675]: Failed to read display number from pipe
Dec 23 15:12:51 riccardo-pc sddm[675]: Display server failed to start. Exiting
Dec 23 15:12:52 riccardo-pc systemd-coredump[684]: Process 675 (sddm) of user 0 dumped core.
                                                   
                                                   Stack trace of thread 675:
                                                   #0  0x00007f10bd619d7f raise (libc.so.6)
                                                   #1  0x00007f10bd604672 abort (libc.so.6)
                                                   #2  0x00007f10bd9d17fc _ZNK14QMessageLogger5fatalEPKcz (libQt5C>
                                                   #3  0x0000558424f2b1f3 n/a (sddm)
                                                   #4  0x0000558424f6ac2e _ZN4SDDM4Seat13createDisplayEi (sddm)
                                                   #5  0x0000558424f6ae72 _ZN4SDDM4SeatC2ERK7QStringP7QObject (sdd>
                                                   #6  0x0000558424f6ce41 _ZN4SDDM11SeatManager10createSeatERK7QSt>
                                                   #7  0x0000558424f6dc62 n/a (sddm)
                                                   #8  0x00007f10bdbecbd0 _ZN11QMetaObject8activateEP7QObjectiiPPv>
                                                   #9  0x0000558424f6beb0 _ZN4SDDM10LogindSeat19canGraphicalChange>
                                                   #10 0x0000558424f6c1c3 n/a (sddm)
                                                   #11 0x00007f10bdbecbd0 _ZN11QMetaObject8activateEP7QObjectiiPPv>
                                                   #12 0x00007f10be4f8900 _ZN23QDBusPendingCallWatcher8finishedEPS>
                                                   #13 0x00007f10be4f8a01 n/a (libQt5DBus.so.5)
                                                   #14 0x00007f10bdbed352 _ZN7QObject5eventEP6QEvent (libQt5Core.s>
                                                   #15 0x00007f10bdbc2c17 _ZN16QCoreApplication15notifyInternal2EP>
                                                   #16 0x00007f10bdbc5ccc _ZN23QCoreApplicationPrivate16sendPosted>
                                                   #17 0x00007f10bdc169d4 n/a (libQt5Core.so.5)
                                                   #18 0x00007f10bc5023cf g_main_context_dispatch (libglib-2.0.so.>
                                                   #19 0x00007f10bc503f89 n/a (libglib-2.0.so.0)
                                                   #20 0x00007f10bc503fce g_main_context_iteration (libglib-2.0.so>
                                                   #21 0x00007f10bdc15fc9 _ZN20QEventDispatcherGlib13processEvents>
                                                   #22 0x00007f10bdbc18cc _ZN10QEventLoop4execE6QFlagsINS_17Proces>
                                                   #23 0x00007f10bdbc9bc6 _ZN16QCoreApplication4execEv (libQt5Core>
                                                   #24 0x0000558424f2eb0a main (sddm)
                                                   #25 0x00007f10bd606223 __libc_start_main (libc.so.6)
                                                   #26 0x0000558424f2ee0a _start (sddm)
                                                   
                                                   Stack trace of thread 676:
                                                   #0  0x00007f10bd6d2c21 __poll (libc.so.6)
                                                   #1  0x00007f10bc503ee0 n/a (libglib-2.0.so.0)
                                                   #2  0x00007f10bc503fce g_main_context_iteration (libglib-2.0.so>
                                                   #3  0x00007f10bdc15fc9 _ZN20QEventDispatcherGlib13processEvents>
                                                   #4  0x00007f10bdbc18cc _ZN10QEventLoop4execE6QFlagsINS_17Proces>
                                                   #5  0x00007f10bda0aeb9 _ZN7QThread4execEv (libQt5Core.so.5)
                                                   #6  0x00007f10be49cba6 n/a (libQt5DBus.so.5)
                                                   #7  0x00007f10bda14f65 n/a (libQt5Core.so.5)
                                                   #8  0x00007f10bd5c8a9d start_thread (libpthread.so.0)
                                                   #9  0x00007f10bd6ddb23 __clone (libc.so.6)
Dec 23 15:12:52 riccardo-pc systemd[1]: Failed to start Simple Desktop Display Manager.

SOLUTION

The system managed to boot with the linux418 kernel, installed using a Manjaro live CD and chroot.

First try to boot to prompt.

At grub menu, press 'e’
Arrow down to linux line
Arrow right past ‘quiet’ and 'splash’
Backspace to remove ‘quiet’ and ‘splash’ taking care not to remove 'rw’
Add ‘3’ (without apostrophes meaning just 3)
Press F10 or ‘ctl’ + ‘x’ to boot
login with password to prompt.

If this boots to prompt, most likely a graphic card, and fix your graphic drivers at prompt.
Easier, safer at prompt than from chroot (and chroot from Elementary won't do anyway, has to be chroot from a manjaro OS).

Good luck.

1 Like

Hello, thank you very much for your answer.
I have removed the "quiet" flag, but can't find any "splash".
I have tried it 2 times:

Removing everything after the linux IMG etc. until RW, deleting so the quiet flag and the "resume=..." parameter: this way I could see the logs and the beginning of the boot but then it randomly freezed while loading something and my screen was there full of green OK's.

The second time I removed only the quiet flag, not the resume parameter, and put the 3 in there

Froze again but at an earlier stage.

Still can't access any command line and, being honest, even if I could I don't have a clear idea of what I should do then...

Thank you

Okay, if it froze booting to prompt, it is a more serious problem than graphics, sddm,...
I don't know what else you can do and hope others here can help you.
But good luck and take care.

do you remember installing or uninstalling anything during your last WORKING manjaro session?
did you do an update on your last session?

do you have a manjaro installation media (usb/dvd) you could use to connect to network and chroot in from?
manjaro-chroot -a

@gohlip But maybe I only edited the grub file in a wrong way? There must be a video error seeing that initial log file...

@dglt Sorry I can't find a rapid way to multi-quote well.
Anyways, right now I'm typing from a live USB of Manjaro, the same Manjaro KDE one I used to install the system few days ago. Right now I chrooted into my main Manjaro and executed a pacman mirror update, pretty randomly.
What should I do for now?

Thanks both, really

EDIT: Oh I forgot to reply.
Yes I messed around with packets of normal software; flathub installations of Gimp and Inkcape, Wine and PlayOnLinux attempts to make the Adobe Creative Cloud work, snapd and various music players to find the best one...and maybe even a system update from the pamac GUI.
That's a lot of stuff maybe? It should not be very good to track down the source of my problems

1 Like

good, now you need to provide some more info. read this post and it will tell you exactly how to do that.

there may be some more specific info needed after but for now read that and post relevant info.

lets see if we can find out, first more info is needed

1 Like

I have edited the first post and now there are more logs of various commands, however there is a lot of stuff and I can't see which could and could not be more useful

could you please post output for
mhwd
mhwd -li
mhwd-kernel -li

[manjaro /]# mhwd
> 0000:01:00.0 (0300:1002:67ff) Display controller ATI Technologies Inc:
--------------------------------------------------------------------------------
                  NAME               VERSION          FREEDRIVER           TYPE
--------------------------------------------------------------------------------
           video-linux            2018.05.04                true            PCI
            video-vesa            2017.03.12                true            PCI


> 0000:04:00.0 (0200:10ec:8168) Network controller Realtek Semiconductor Co., Ltd.:
--------------------------------------------------------------------------------
                  NAME               VERSION          FREEDRIVER           TYPE
--------------------------------------------------------------------------------
         network-r8168            2016.04.20                true            PCI


> 0000:00:02.0 (0380:8086:0152) Display controller Intel Corporation:
--------------------------------------------------------------------------------
                  NAME               VERSION          FREEDRIVER           TYPE
--------------------------------------------------------------------------------
           video-linux            2018.05.04                true            PCI

[manjaro /]# mhwd -li
> Installed PCI configs:
--------------------------------------------------------------------------------
                  NAME               VERSION          FREEDRIVER           TYPE
--------------------------------------------------------------------------------
           video-linux            2018.05.04                true            PCI
         network-r8168            2016.04.20                true            PCI


Warning: No installed USB configs!
[manjaro /]# mhwd-kernel -li
Currently running: 4.19.0-3-MANJARO (linux419)
The following kernels are installed in your system:
   * linux418
   * linux419

The linux418 was installed right now in a desperate attempt to change something for next boot, but it is freshly installed and I have never used it until now. Right before this installation the only kernel was the linux419 and that's the only one I have ever used

ok so you have not tried to boot the 4.18 yet? if not, try it now and if it doesnt have any effect then chroot back in and we can try re-installing video drivers and try some kernel parameters to get it to boot

1 Like

Okay I'm rebooting and I'll let you know, anyways I'm answering right now before I have already tried to reinstall the video drivers twice from the Elementary chroot so maybe it's not the best option (?)
Anyways, I'm rebooting...I'll let you know and thank you

EDIT: Okay, I'm in. Writing right from my main Manjaro install, all my files, work and widgets there etc.
So booting from the never-used 4.18 kernel worked. But why, since I have used the 4.19 from the start and it has worked well for 4 days?

Should I consider this a permanent solution? Like, sticking to the 4.18 until some update fixes the newer ones? How should I behave now?

Thank you

yes, use what works. 4.18 is EOL iirc. you could also uninstall/reinstall 4.19 now that you have 4.18 working if you wanted to try it. also its recommended to have 2 kernels installed in case one stops working for any reason, you have a backup. its up to you.
sudo mhwd-kernel -r linux419
sudo mhwd-kernel -i linux419

also, after you are sure all is working well i highly suggest you install timeshift since its very reliable, easy to use and setup and it does periodic rsync backups as often as you set it to automatically. so in the future when something goes wrong you can use timeshift either from your install or even from a bootable usb or chroot. it has saved my installs more than a few times and im also much less concerned when making dangerous changes that i would otherwise not do if i didnt have a backup solution ready, just always try and make an honest attempt to figure out what went wrong before using a backup so you know how and why so you dont repeat it again.

1 Like

Even after being reinstalled, the linux419 managed to crash again.
I'm on 4.18 now; if it's EOL what version would you suggest?

Anyways thank you for your help and your time, I'm marking your answer as the solution.

I always go with LTS - long term support.
Before 4.19 are:

4.14
4.9

There was a talk that 4.9 may be removed from Manjaro?!?
Anyway, next I would try 4.14

Have you tried to re-install linux419 and linux-firmware? Also does the kernel trigger a initram rebuild for you?

I have installed the 4.14 and will try it. The graphical client still shows the 4.9, but I didn't try installing it.
Thank you

I don't know what a "initram rebuild" does, but I remember having given a command that did exactly this on my first run with the Elementary OS chroot (following a guide). This happened before I tried reinstalling linux419.
Because yes, after having successfully booted from the linux418 I tried reinstalling linux419 and nothing changed.
I have never touched linux-firmware.

What should I do to give it a try, what commands? And most important, in which environment?
My main manjaro running with linux418 or a live CD?

Thanks

always from manjaro if you can.

pacman -Syu linux419 linux-firmware
mkinitcpio -p linux419

could you tell us what firmware version is currently installed on your system, if that does not work for you?

1 Like

I executed the 2 commands and I'm about to reboot, but I'm writing before that because I don't exactly know what you mean by firmware version (in the context of Manjaro and Linux at least).
What info should I provide to you if at the next reboot kernel 4.19 still won't work

Thanks

EDIT: Even after those commands, system won't boot with 4.19.

And 4.14 doesn't work too! While I was there I tried it and I'm stuck on a black screen, but at least this time there was a blinking cursor that after some seconds stopped and now it's there doing nothing, like froze.

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