I booted 6.2-rc2 + patch with rd.driver.blacklist=amdgpu on the kernel 
command line to prevent amdgpu from being started while the initramfs 
was in use. The black screen problem happened later in the boot. I 
pressed sysrq+alt+s,u,b to do an emergency sync, remount read-only, and 
reboot. The journal for that boot was shown on the next boot. The two 
warnings which I previously reported weren't shown in the journal, but 
the same null pointer dereference which made amdgpu crash happened. I'm 
attaching the kernel log from the journal of that boot.