For some reason I was able to compile v5.4 and v5.5 from torvalds branchs with `make -j$(nproc) deb-pkg` but starting with v5.6 I had to use `make -j$(nproc) bindeb-pkg`, in the end I lacked some modules (like my network driver, that did not helped me) but radeon one was there so tests could have been done.

The GNOME desktop opened properly with 5.4, 5.5, 5.6, 5.7 and 5.8. But when v5.9, I just got the desktop (GDM is configured to autologin) restarting again and again, only showing me a mouse cursor before dying.

The errors in dmesg were similar to the one I found with PCI devices (not AGP ones!) on the same AMD K8 or K10-based motherboard I reproduce issue with AGP devices.

Also, the errors in vanilla 5.9 look to be the same as the one seen in 5.10-rc1 from mainline PPA.

Here is a sample of captured dmesg error on vanilla 5.9:

```
[    5.242322] [drm:r600_ring_test [radeon]] *ERROR* radeon: ring 0 test failed (scratch(0x8504)=0xCAFEDEAD)
[    5.242359] radeon 0000:01:00.0: disabling GPU acceleration
…

[   34.558885] ------------[ cut here ]------------
[   34.558889] trying to bind memory to uninitialized GART !
[   34.559048] WARNING: CPU: 1 PID: 2516 at drivers/gpu/drm/radeon/radeon_gart.c:299 radeon_gart_bind+0xdf/0xf0 [radeon]
[   34.559050] Modules linked in: zram snd_usb_audio snd_hda_intel snd_intel_dspcfg snd_hda_codec snd_usbmidi_lib snd_hda_core snd_hwdep snd_pcm snd_seq_midi kvm_amd snd_seq_midi_event ccp joydev kvm snd_seq snd_rawmidi input_leds snd_timer snd_seq_device snd soundcore k10temp mac_hid serio_raw binfmt_misc sch_fq_codel parport_pc ppdev lp parport ip_tables x_tables btrfs blake2b_generic zstd_compress raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx libcrc32c xor raid6_pq raid1 raid0 multipath linear uas usb_storage hid_generic usbhid hid radeon i2c_algo_bit drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm drm psmouse forcedeth i2c_nforce2
[   34.559107] CPU: 1 PID: 2516 Comm: gnome-shell Not tainted 5.9.0 #1
[   34.559109] Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./AM2NF3-VSTA, BIOS P3.20 10/09/2009
[   34.559178] RIP: 0010:radeon_gart_bind+0xdf/0xf0 [radeon]
[   34.559184] Code: 00 48 89 ef 48 8b 40 60 e8 0e 2f 44 df 31 c0 48 83 c4 08 5b 5d 41 5c 41 5d 41 5e 41 5f c3 48 c7 c7 38 6f 6b c0 e8 23 0c 6d de <0f> 0b b8 ea ff ff ff eb dc 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00
[   34.559187] RSP: 0018:ffffc030838f7a28 EFLAGS: 00010282
[   34.559191] RAX: 0000000000000000 RBX: ffffa0cf6b88eb80 RCX: 0000000000000027
[   34.559193] RDX: 0000000000000027 RSI: 0000000000000086 RDI: ffffa0cf6fc98d08
[   34.559196] RBP: ffffc030838f7b28 R08: ffffa0cf6fc98d00 R09: 0000000000000004
[   34.559198] R10: 0000000000000000 R11: 0000000000000001 R12: ffffc030838f7b28
[   34.559201] R13: ffffa0cf6a622868 R14: ffffa0cf6c7cc6e8 R15: ffffc030838f7b28
[   34.559204] FS:  00007f46ae245cc0(0000) GS:ffffa0cf6fc80000(0000) knlGS:0000000000000000
[   34.559207] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   34.559210] CR2: 000056494261c1c8 CR3: 000000040bfe6000 CR4: 00000000000006e0
[   34.559212] Call Trace:
[   34.559286]  radeon_ttm_backend_bind+0x58/0x210 [radeon]
[   34.559305]  ttm_tt_bind+0x32/0x60 [ttm]
[   34.559321]  ttm_bo_handle_move_mem+0x236/0x590 [ttm]
[   34.559339]  ttm_bo_validate+0x16c/0x180 [ttm]
[   34.559407]  ? drm_ioctl_kernel+0xe9/0xf0 [drm]
[   34.559422]  ttm_bo_init_reserved+0x2ae/0x320 [ttm]
[   34.559438]  ttm_bo_init+0x6d/0xf0 [ttm]
[   34.559504]  ? radeon_update_memory_usage.isra.0+0x50/0x50 [radeon]
[   34.559569]  radeon_bo_create+0x184/0x210 [radeon]
[   34.559634]  ? radeon_update_memory_usage.isra.0+0x50/0x50 [radeon]
[   34.559703]  radeon_gem_object_create+0xa9/0x180 [radeon]
[   34.559773]  ? radeon_gem_pwrite_ioctl+0x20/0x20 [radeon]
[   34.559840]  radeon_gem_create_ioctl+0x66/0x120 [radeon]
[   34.559850]  ? tomoyo_path_number_perm+0x66/0x1d0
[   34.559918]  ? radeon_gem_pwrite_ioctl+0x20/0x20 [radeon]
[   34.559968]  drm_ioctl_kernel+0xaa/0xf0 [drm]
[   34.560021]  drm_ioctl+0x1ec/0x390 [drm]
[   34.560090]  ? radeon_gem_pwrite_ioctl+0x20/0x20 [radeon]
[   34.560152]  radeon_drm_ioctl+0x49/0x80 [radeon]
[   34.560160]  __x64_sys_ioctl+0x83/0xb0
[   34.560167]  do_syscall_64+0x33/0x80
[   34.560174]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[   34.560179] RIP: 0033:0x7f46b369550b
[   34.560183] Code: 0f 1e fa 48 8b 05 85 39 0d 00 64 c7 00 26 00 00 00 48 c7 c0 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 55 39 0d 00 f7 d8 64 89 01 48
[   34.560186] RSP: 002b:00007ffdb7421658 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
[   34.560189] RAX: ffffffffffffffda RBX: 00007ffdb74216d0 RCX: 00007f46b369550b
[   34.560192] RDX: 00007ffdb74216d0 RSI: 00000000c020645d RDI: 000000000000000e
[   34.560194] RBP: 00000000c020645d R08: 0000000000000011 R09: 0000000000000005
[   34.560197] R10: 000056494245c010 R11: 0000000000000246 R12: 0000000000001000
[   34.560199] R13: 000000000000000e R14: 0000000000010000 R15: 0000000000001000
[   34.560205] ---[ end trace 9ea277f1e2a7c575 ]---
[   34.560271] [drm:radeon_ttm_backend_bind [radeon]] *ERROR* failed to bind 16 pages at 0x00000000
[   34.560363] [drm:radeon_gem_object_create [radeon]] *ERROR* Failed to allocate GEM object (65536, 2, 4096, -22)
```