I don't know if this is a good place to continue this discussion, but as it seems most of the previous discussion of the issues relating to the efifb change is in this thread it might make sense to continue here even though the affected kernels are no longer opt-in.
Just ran into the 5.15 kernel resulting in no display issue after upgrading to a 7.1 system to 7.2:
pve-kernel-5.15.30-2-pve 5.15.30-3
pve-kernel-helper 7.2-2
This is on a machine with an Asrock Rack motherboard with ASPEED graphics.
It appears that "simplefb" is indeed loaded early on, as intended, but that does not result in any display output during early boot (initramfs etc)
[ 11.456186] simple-framebuffer simple-framebuffer.0: framebuffer at 0xfb000000, 0x1d5000 bytes
[ 11.456191] simple-framebuffer simple-framebuffer.0: format=a8r8g8b8, mode=800x600x32, linelength=3200
[ 11.456256] Console: switching to colour frame buffer device 100x37
[ 11.485771] simple-framebuffer simple-framebuffer.0: fb0: simplefb registered!
However later in the boot process "ast" is loaded and display is restored (I assume that is what does it, anyway).
[ 30.872558] ast 0000:29:00.0: [drm] Using P2A bridge for configuration
[ 30.890569] ast 0000:29:00.0: [drm] AST 2500 detected
[ 30.908147] ast 0000:29:00.0: [drm] Analog VGA only
[ 30.925632] ast 0000:29:00.0: [drm] dram MCLK=800 Mhz type=7 bus_width=16
[ 30.943543] [drm] Initialized ast 0.1.0 20120228 for 0000:29:00.0 on minor 0
This is as it appears over IPMI/ipkvm, I have no idea what it looks like on the local console (that is rather pointless, anyway).
I do know, however, that with the 5.13 / efifb setup this problem did not occur.
I hope there is some way to get this sorted.
I suppose one could get ast (and I guess it's firmware?) into initramfs, but that seems a bit messy, and I assume the intention is that simplefb should be able to work anywhere?
