OK in F43, but regression in F41 & F42 using radeon.cik_support=0 amdgpu.cik_support=1

Earlier today I cloned an F42 to another partition in same PC, then did a dn5
system-upgrade --releasver=43 with kernel locked, then installed the 42 6.16.6
testing kernel. Satisfactory end product:
# pinxi -GSaz --za --hostname
System:
  Host: ga88x Kernel: 6.16.6-200.fc42.x86_64 arch: x86_64 bits: 64
    compiler: gcc v: 15.2.1 clocksource: tsc avail: hpet,acpi_pm
    parameters: BOOT_IMAGE=/boot/vmlinuz root=LABEL=<filter> noresume
    selinux=0 audit=0 ipv6.disable=1 net.ifnames=0 mitigations=auto
    consoleblank=0 radeon.cik_support=0 amdgpu.cik_support=1
  Desktop: TDE (Trinity) v: R14.1.4 tk: Qt v: 3.5.0 wm: Twin v: 3.0
    with: kicker vt: 7 dm: 1: TDM 2: XDM Distro: Fedora Linux 43 (Forty Three
    Prerelease)
Graphics:
  Device-1: Advanced Micro Devices [AMD/ATI] Kaveri [Radeon R7 Graphics]
    vendor: Gigabyte driver: amdgpu v: kernel alternate: radeon arch: GCN-2
    code: Sea Islands process: GF/TSMC 16-28nm built: 2013-17 ports:
    active: DVI-D-1,HDMI-A-1 empty: VGA-1 bus-ID: 00:01.0 chip-ID: 1002:130f
    class-ID: 0300
  Display: x11 server: X.Org v: 21.1.18 compositor: Twin v: 3.0 driver: X:
    loaded: amdgpu unloaded: modesetting alternate: fbdev,vesa dri: radeonsi
    gpu: amdgpu display-ID: :0 screens: 1
  Screen-1: 0 s-res: 3600x1200 s-dpi: 120 s-size: 762x254mm (30.00x10.00")
    s-diag: 803mm (31.62")
  Monitor-1: DVI-D-1 mapped: DVI-D-0 pos: right model: Dell P2213
    serial: <filter> built: 2013 res: mode: 1680x1050 hz: 60 scale: 100% (1)
    dpi: 90 gamma: 1.2 size: 473x296mm (18.62x11.65") diag: 558mm (22")
    ratio: 16:10 modes: max: 1680x1050 min: 720x400
  Monitor-2: HDMI-A-1 mapped: HDMI-A-0 pos: primary,left model: NEC EA243WM
    serial: <filter> built: 2011 res: mode: 1920x1200 hz: 60 scale: 100% (1)
    dpi: 94 gamma: 1.2 size: 519x324mm (20.43x12.76") diag: 612mm (24.1")
    ratio: 16:10 modes: max: 1920x1200 min: 640x480
  API: EGL v: 1.5 hw: drv: amd radeonsi platforms: device: 0 drv: radeonsi
    device: 1 drv: swrast gbm: drv: radeonsi surfaceless: drv: radeonsi x11:
    drv: radeonsi inactive: wayland
  API: OpenGL v: 4.6 compat-v: 4.5 vendor: amd mesa v: 25.1.4 glx-v: 1.4
    direct-render: yes renderer: AMD Radeon R7 Graphics (radeonsi kaveri ACO
    DRM 3.64 6.16.6-200.fc42.x86_64) device-ID: 1002:130f memory: 1000 MiB
    unified: no
  API: Vulkan v: 1.4.321 layers: 1 device: 0 type: integrated-gpu name: AMD
    Radeon R7 Graphics (RADV KAVERI) driver: mesa radv v: 25.1.4
    device-ID: 1002:130f surfaces: N/A device: 1 type: cpu name: llvmpipe
    (LLVM 20.1.8 256 bits) driver: mesa llvmpipe v: 25.1.4 (LLVM 20.1.8)
    device-ID: 10005:0000 surfaces: N/A
  Info: Tools: api: clinfo, eglinfo, glxinfo, vulkaninfo
    x11: xdpyinfo, xprop, xrandr
#
The reason for the post is in the subject. radeon.cik_support=0
amdgpu.cik_support=1 are cmdline options to have amdgpu GPU module in control
instead of radeon with Sea Islands GPUs. Before reporting a bug, I'd like
confirmation that the problem with 41 and 42 is in the kernel, as it seems perhaps
elsewhere, but I don't what the options for elsewhere would be. In order to boot
with working KMS, radeon.cik_support=0 amdgpu.cik_support=1 must be omitted from
kernel cmdline, which results in using the radeon kernel driver. 41 had working
KMS with 6.14.11 4 weeks ago and for several years, but not today with 6.15.10; 42
with 6.12.41 4 weeks ago and for several years, but not today with 6.15.10. All
are using the same firmware version 20250808. 43 is fine on both 6.15.10 and 6.16.6.

I tried in 42 kernel option modprobe.blacklist=radeon along with
radeon.cik_support=0 amdgpu.cik_support=1, which didn't help, but with instead
modprobe.blacklist=radeon amdgpu.cik_support=1 it's working as expected. 6.12.45
in openSUSE Slowroll and 6.12.44 in Mageia Cauldron are also working as expected.
-- 
Evolution as taught in public schools is, like religion,
	based on faith, not based on science.

 Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

Felix Miata
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