[Regression] Kernel 4.19.x + linux-firmware 20190514 + Vega 64: boot fails

Submitted by Aleksandr Mezin @amezin

Assigned to Default DRI bug account

Link to original bug (#110733)

Description

Copying https://bugzilla.kernel.org/show_bug.cgi?id=203627 here, as I'm not sure where to report the issue (and got no response in kernel bugzilla so far)

After linux-firmware upgrade from 4b6cf2bd1a9d53caa087403d943e7695009c1d0c to 711d3297bac870af42088a467459a0634c1970ca (20190514), 4.19 kernels (at least 4.19.40-4.19.45) don't boot anymore. Early during boot the monitor turns off, and, apparently, the system hangs. Can't connect over SSH, SysRq keys don't work. Also the failed boot attempt doesn't get recorded by journald.

Kernels 5.0 and 5.1 still boot completely fine. Also, 4.19 kernels boot if I downgrade firmware back to 4b6cf2bd1a9d53caa087403d943e7695009c1d0c.

Apparently, these problems are caused by https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/commit/?id=2579167548be33afb1fe2a9a5c141561ee5a8bbe

GPU: RX Vega 64 (Sapphire Nitro+, vbios_version: 113-D0500110-O01)
Distro: Arch Linux
Archlinux bug: https://bugs.archlinux.org/task/62666