radeon driver doesn't work

[Hiroshi TAKENAKA]

With linux-image later than 5.15.0-73-generic Ubuntu 20.04 blacks out at booting.

My hardwware is iMac 21 inch mid 2011 (CPU Core i3 540, 16GB DRAM). The video driver shown by lshw is Mobility Radeon HD 4670.

After the drives are checked, the screen blacks out. However, the system itself seems to boot normally. I can ssh to it from other machines.

Now I use linux-image-5.15.0-73-generic, which is the latest kernel for radeon to work normally.

The followings are the outputs of "journalctl -b | grep radeon" of 5.15.0-84-generic and 5.15.0-73-generic.
Comparing with the log of 5.15.0-73-generic, systemd seems to stop 5Screen Backlight Brightness with 15.0-84-generic.

*** "journalctl -b | grep radeon" of 5.15.0-84-generic ***

Sep 24 21:33:13 ubuntu2004-imac kernel: [drm] radeon kernel modesetting enabled.
Sep 24 21:33:13 ubuntu2004-imac kernel: radeon 0000:01:00.0: vgaarb: deactivate vga console
Sep 24 21:33:13 ubuntu2004-imac kernel: radeon 0000:01:00.0: No more image in the PCI ROM
Sep 24 21:33:13 ubuntu2004-imac kernel: radeon 0000:01:00.0: VRAM: 256M 0x0000000000000000 - 0x000000000FFFFFFF (256M used)
Sep 24 21:33:13 ubuntu2004-imac kernel: radeon 0000:01:00.0: GTT: 1024M 0x0000000010000000 - 0x000000004FFFFFFF
Sep 24 21:33:13 ubuntu2004-imac kernel: [drm] radeon: 256M of VRAM memory ready
Sep 24 21:33:13 ubuntu2004-imac kernel: [drm] radeon: 1024M of GTT memory ready.
Sep 24 21:33:13 ubuntu2004-imac kernel: [drm] radeon: dpm initialized
Sep 24 21:33:13 ubuntu2004-imac kernel: [drm] enabling PCIE gen 2 link speeds, disable with radeon.pcie_gen2=0
Sep 24 21:33:13 ubuntu2004-imac kernel: radeon 0000:01:00.0: WB enabled
Sep 24 21:33:13 ubuntu2004-imac kernel: radeon 0000:01:00.0: fence driver on ring 0 use gpu addr 0x0000000010000c00
Sep 24 21:33:13 ubuntu2004-imac kernel: radeon 0000:01:00.0: fence driver on ring 3 use gpu addr 0x0000000010000c0c
Sep 24 21:33:13 ubuntu2004-imac kernel: radeon 0000:01:00.0: fence driver on ring 5 use gpu addr 0x000000000005c598
Sep 24 21:33:13 ubuntu2004-imac kernel: radeon 0000:01:00.0: radeon: MSI limited to 32-bit
Sep 24 21:33:13 ubuntu2004-imac kernel: radeon 0000:01:00.0: radeon: using MSI.
Sep 24 21:33:13 ubuntu2004-imac kernel: [drm] radeon: irq initialized.
Sep 24 21:33:13 ubuntu2004-imac kernel: [drm] radeon atom DIG backlight initialized
Sep 24 21:33:13 ubuntu2004-imac kernel: fbcon: radeondrmfb (fb0) is primary device
Sep 24 21:33:13 ubuntu2004-imac kernel: radeon 0000:01:00.0: [drm] fb0: radeondrmfb frame buffer device
Sep 24 21:33:13 ubuntu2004-imac kernel: [drm] Initialized radeon 2.50.0 20080528 for 0000:01:00.0 on minor 0
Sep 24 21:33:06 ubuntu2004-imac systemd[1]: Starting Load/Save Screen Backlight Brightness of backlight:radeon_bl0...
Sep 24 21:33:06 ubuntu2004-imac systemd[1]: Finished Load/Save Screen Backlight Brightness of backlight:radeon_bl0.
Sep 24 21:34:05 ubuntu2004-imac systemd[1]: Stopping Load/Save Screen Backlight Brightness of backlight:radeon_bl0...
Sep 24 21:34:05 ubuntu2004-imac systemd[1]: systemd-backlight@backlight:radeon_bl0.service: Succeeded.
Sep 24 21:34:05 ubuntu2004-imac systemd[1]: Stopped Load/Save Screen Backlight Brightness of backlight:radeon_bl0.

*** end ***

*** "journalctl -b | grep radeon" of 5.15.0-73-generic ***

Sep 24 21:35:27 ubuntu2004-imac kernel: [drm] radeon kernel modesetting enabled.
Sep 24 21:35:27 ubuntu2004-imac kernel: radeon 0000:01:00.0: vgaarb: deactivate vga console
Sep 24 21:35:27 ubuntu2004-imac kernel: radeon 0000:01:00.0: No more image in the PCI ROM
Sep 24 21:35:27 ubuntu2004-imac kernel: radeon 0000:01:00.0: VRAM: 256M 0x0000000000000000 - 0x000000000FFFFFFF (256M used)
Sep 24 21:35:27 ubuntu2004-imac kernel: radeon 0000:01:00.0: GTT: 1024M 0x0000000010000000 - 0x000000004FFFFFFF
Sep 24 21:35:27 ubuntu2004-imac kernel: [drm] radeon: 256M of VRAM memory ready
Sep 24 21:35:27 ubuntu2004-imac kernel: [drm] radeon: 1024M of GTT memory ready.
Sep 24 21:35:27 ubuntu2004-imac kernel: [drm] radeon: dpm initialized
Sep 24 21:35:27 ubuntu2004-imac kernel: [drm] enabling PCIE gen 2 link speeds, disable with radeon.pcie_gen2=0
Sep 24 21:35:27 ubuntu2004-imac kernel: radeon 0000:01:00.0: WB enabled
Sep 24 21:35:27 ubuntu2004-imac kernel: radeon 0000:01:00.0: fence driver on ring 0 use gpu addr 0x0000000010000c00
Sep 24 21:35:27 ubuntu2004-imac kernel: radeon 0000:01:00.0: fence driver on ring 3 use gpu addr 0x0000000010000c0c
Sep 24 21:35:27 ubuntu2004-imac kernel: radeon 0000:01:00.0: fence driver on ring 5 use gpu addr 0x000000000005c598
Sep 24 21:35:27 ubuntu2004-imac kernel: radeon 0000:01:00.0: radeon: MSI limited to 32-bit
Sep 24 21:35:27 ubuntu2004-imac kernel: radeon 0000:01:00.0: radeon: using MSI.
Sep 24 21:35:27 ubuntu2004-imac kernel: [drm] radeon: irq initialized.
Sep 24 21:35:27 ubuntu2004-imac kernel: [drm] radeon atom DIG backlight initialized
Sep 24 21:35:27 ubuntu2004-imac kernel: fbcon: radeondrmfb (fb0) is primary device
Sep 24 21:35:27 ubuntu2004-imac kernel: radeon 0000:01:00.0: [drm] fb0: radeondrmfb frame buffer device
Sep 24 21:35:27 ubuntu2004-imac kernel: [drm] Initialized radeon 2.50.0 20080528 for 0000:01:00.0 on minor 0
Sep 24 21:35:17 ubuntu2004-imac systemd[1]: Starting Load/Save Screen Backlight Brightness of backlight:radeon_bl0...
Sep 24 21:35:17 ubuntu2004-imac systemd[1]: Finished Load/Save Screen Backlight Brightness of backlight:radeon_bl0.
Sep 24 21:36:11 ubuntu2004-imac /usr/lib/gdm3/gdm-x-session[2595]: loading driver: radeon
Sep 24 21:36:11 ubuntu2004-imac /usr/lib/gdm3/gdm-x-session[2595]: (==) Matched radeon as autoconfigured driver 0
Sep 24 21:36:11 ubuntu2004-imac /usr/lib/gdm3/gdm-x-session[2595]: (II) LoadModule: "radeon"
Sep 24 21:36:11 ubuntu2004-imac /usr/lib/gdm3/gdm-x-session[2595]: (II) Loading /usr/lib/xorg/modules/drivers/radeon_drv.so
Sep 24 21:36:11 ubuntu2004-imac /usr/lib/gdm3/gdm-x-session[2595]: (II) Module radeon: vendor="X.Org Foundation"

*** end ***

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: linux-image-5.15.0-84-generic 5.15.0-84.93~20.04.1
ProcVersionSignature: Ubuntu 5.15.0-73.80~20.04.1-generic 5.15.98
Uname: Linux 5.15.0-73-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.27
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Tue Sep 26 18:45:50 2023
InstallationDate: Installed on 2020-06-09 (1203 days ago)
InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=ja_JP.UTF-8
 SHELL=/bin/bash
SourcePackage: linux-signed-hwe-5.15
UpgradeStatus: No upgrade log present (probably fresh install)