Problems with kernel modesetting

I’m having trouble with my display, specifically drm/kernel modesetting, on the latest nixos-unstable. The following log messages are present on a working system (nixpkgs rev 83d011cc8950bb1d27588e3fdf534094973948e1):

[drm] radeon kernel modesetting enabled.
fb0: switching to radeondrmfb from EFI VGA
[drm] initializing kernel modesetting (CAICOS 0x1002:0x6778 0x1028:0x2120 0x00).
[drm] Detected VRAM RAM=1024M, BAR=256M
[drm] RAM width 64bits DDR
[drm] radeon: 1024M of VRAM memory ready
[drm] radeon: 1024M of GTT memory ready.
[drm] Loading CAICOS Microcode
[drm] Internal thermal controller without fan control
[drm] radeon: dpm initialized
[drm] GART: num cpu pages 262144, num gpu pages 262144
[drm] enabling PCIE gen 2 link speeds, disable with radeon.pcie_gen2=0
[drm] PCIE GART of 1024M enabled (table at 0x0000000000162000).
[drm] radeon: irq initialized.
[drm] ring test on 0 succeeded in 2 usecs
[drm] ring test on 3 succeeded in 8 usecs
[drm] ring test on 5 succeeded in 2 usecs
[drm] UVD initialized successfully.
[drm] ib test on ring 0 succeeded in 0 usecs
[drm] ib test on ring 3 succeeded in 0 usecs
[drm] ib test on ring 5 succeeded
[drm] Radeon Display Connectors
[drm] Connector 0:
[drm]   DP-1
[drm]   HPD2
[drm]   DDC: 0x6460 0x6460 0x6464 0x6464 0x6468 0x6468 0x646c 0x646c
[drm]   Encoders:
[drm] Connector 1:
[drm]   DVI-I-1
[drm]   HPD4
[drm]   DDC: 0x6450 0x6450 0x6454 0x6454 0x6458 0x6458 0x645c 0x645c
[drm]   Encoders:
[drm] fb mappable at 0xE0363000
[drm] vram apper at 0xE0000000
[drm] size 8294400
[drm] fb depth is 24
[drm]    pitch is 7680
fbcon: radeondrmfb (fb0) is primary device
radeon 0000:01:00.0: [drm] fb0: radeondrmfb frame buffer device
[drm] Initialized radeon 2.50.0 20080528 for 0000:01:00.0 on minor 0

Nixpkgs rev bb52ac0cb0b03df4d83ea4fb99efc3ea7e148b0b (or latest unstable) does not produce any of these log messages. When I boot up, my display is stuck at a low resolution and I cannot launch my wayland compositor. I am running the latest kernel in nixpkgs, 5.11.7. I am passing my kernel the video parameter (video=DVI-I-1:1920x1080@60) because it defaults to a 75Hz refresh rate which is unsupported by my monitor. My video card is an AMD Caicos GPU. The relevant lspci line:

01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Caicos XT [Radeon HD 7470/8470 / R5 235/310 OEM]

Any suggestions would be appreciated.

Solved. The kernel module “radeon” had to be added to boot.initrd.kernelModules