Arch Linux

Description:
When booting early KMS sets resolution somehow improperly. I attached example of what it looks like. Appears that columns of pixels are skipped and other visible columns are shifted left. Motherboard boot splashscreen and text of bootloader (systemd-boot) are displayed properly, as soon as Xorg kicks in everything is again displayed properly.


Additional info:
* MSI Radeon™ RX 580 GAMING X 8G (this is how card was branded, even if lspci says its RX 470/480, no idea what is going on here)
* ASUS MG279Q 2560x1440 monitor connected through hdmi
* Opensource amdgpu driver
* early KMS ( MODULES="nls_iso8859-1 ext2 nls_cp437 nls_utf8 vfat cryptd aes_x86_64 aesni_intel pci_stub vfio vfio_iommu_type1 vfio_pci vfio_virqfd kvm kvm_intel amdgpu" )

03:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Ellesmere [Radeon RX 470/480] [1002:67df] (rev e7) (prog-if 00 [VGA controller])
Subsystem: Micro-Star International Co., Ltd. [MSI] Device [1462:3417]
Physical Slot: 6
Flags: bus master, fast devsel, latency 0, IRQ 31, NUMA node 0
Memory at c0000000 (64-bit, prefetchable) [size=256M]
Memory at d0000000 (64-bit, prefetchable) [size=2M]
I/O ports at e000 [size=256]
Memory at df100000 (32-bit, non-prefetchable) [size=256K]
Expansion ROM at 000c0000 [disabled] [size=128K]
Capabilities: [48] Vendor Specific Information: Len=08 <?>
Capabilities: [50] Power Management version 3
Capabilities: [58] Express Legacy Endpoint, MSI 00
Capabilities: [a0] MSI: Enable+ Count=1/1 Maskable- 64bit+

Steps to reproduce: happens always when booting with this combination of hardware and amdgpu driver without any special setup.


I also tried various combinations of video= and drm_kms_helper.edid_firmware= boot parameters but nothing had any effect. This issue surfaced after getting AMD card. Before i was using nvidia card with proprietary driver and this monitor displayed boot text properly, although in low resolution. In attached dmesg log you can see logs of DMAR spam. When troubleshooting that i disabled relevant features and DMAR no longer spewed any errors, however it did not affect display of boot text output and it still was messed up. It also prevented me from using VMs with passed-through so that is why DMAR stuff is enabled with all the error spam.