Ubuntu 20.04 在启动高于 5.15.0-74 的内核时会死机。现在我将内核锁定为 5.15.0-73-generic。
我的硬件是 2011 年中期的 iMac 21 英寸（CPU Core i3 540，16GB DRAM）。瘦身是 Mobility Radeon HD 4670。
检查完驱动器后，屏幕变为空白状态。但是，系统本身似乎可以正常启动。我可以从其他机器 ssh 到它。
以下journalctl -b --no-pager | grep radeon是最新内核 5.15.0-84-generic和旧内核 5.15.0-73-generic。
使用最新内核，systemd似乎停止了屏幕背光亮度。
5.15.0-84-通用
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.
5.15.0-73-通用
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"