After much trial and error, I've narrowed the issue down to the following. My video card drops its signal to my monitor, likely when the framebuffer kicks in. Though I have neutered both splash and quiet, the entries still race by so quickly that this is no more than an educated guess, but it conforms to that moment in the sequence when I boot my other 20.04 partition.
The salient info follows:
Driver: Radeon
Discrete video card:
Code:
duckhook@Zeus:~$ sudo lspci -vk | grep -iA20 vga
[sudo] password for duckhook:
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Tahiti PRO [Radeon HD 7950/8950 OEM / R9 280] (prog-if 00 [VGA controller])
Subsystem: Hightech Information System Ltd. Tahiti PRO [Radeon HD 7950/8950 OEM / R9 280]
Flags: bus master, fast devsel, latency 0, IRQ 56
Memory at d0000000 (64-bit, prefetchable) [size=256M]
Memory at fbe00000 (64-bit, non-prefetchable) [size=256K]
I/O ports at e000 [size=256]
Expansion ROM at 000c0000 [disabled] [size=128K]
Capabilities: [48] Vendor Specific Information: Len=08 <?>
Capabilities: [50] Power Management version 3
Capabilities: [58] Express Legacy Endpoint, MSI 00
Capabilities: [a0] MSI: Enable+ Count=1/1 Maskable- 64bit+
Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1 Len=010 <?>
Capabilities: [150] Advanced Error Reporting
Capabilities: [270] Secondary PCI Express
Capabilities: [2b0] Address Translation Service (ATS)
Capabilities: [2c0] Page Request Interface (PRI)
Capabilities: [2d0] Process Address Space ID (PASID)
Kernel driver in use: radeon
Kernel modules: radeon, amdgpu
Salient log items:
Code:
duckhook@Zeus:~$ sudo journalctl -b | grep radeon | grep kernel
Nov 15 18:49:01 Zeus kernel: [drm] radeon kernel modesetting enabled.
Nov 15 18:49:01 Zeus kernel: fb0: switching to radeondrmfb from EFI VGA
Nov 15 18:49:01 Zeus kernel: radeon 0000:01:00.0: vgaarb: deactivate vga console
Nov 15 18:49:01 Zeus kernel: radeon 0000:01:00.0: VRAM: 3072M 0x0000000000000000 - 0x00000000BFFFFFFF (3072M used)
Nov 15 18:49:01 Zeus kernel: radeon 0000:01:00.0: GTT: 2048M 0x00000000C0000000 - 0x000000013FFFFFFF
Nov 15 18:49:01 Zeus kernel: [drm] radeon: 3072M of VRAM memory ready
Nov 15 18:49:01 Zeus kernel: [drm] radeon: 2048M of GTT memory ready.
Nov 15 18:49:01 Zeus kernel: [drm] radeon: dpm initialized
Nov 15 18:49:01 Zeus kernel: radeon 0000:01:00.0: WB enabled
Nov 15 18:49:01 Zeus kernel: radeon 0000:01:00.0: fence driver on ring 0 use gpu addr 0x00000000c0000c00 and cpu addr 0x00000000a217189e
Nov 15 18:49:01 Zeus kernel: radeon 0000:01:00.0: fence driver on ring 1 use gpu addr 0x00000000c0000c04 and cpu addr 0x0000000050fe85a6
Nov 15 18:49:01 Zeus kernel: radeon 0000:01:00.0: fence driver on ring 2 use gpu addr 0x00000000c0000c08 and cpu addr 0x0000000020952302
Nov 15 18:49:01 Zeus kernel: radeon 0000:01:00.0: fence driver on ring 3 use gpu addr 0x00000000c0000c0c and cpu addr 0x000000009ceb52ec
Nov 15 18:49:01 Zeus kernel: radeon 0000:01:00.0: fence driver on ring 4 use gpu addr 0x00000000c0000c10 and cpu addr 0x0000000091a1317a
Nov 15 18:49:01 Zeus kernel: radeon 0000:01:00.0: fence driver on ring 5 use gpu addr 0x0000000000075a18 and cpu addr 0x00000000fadfaf36
Nov 15 18:49:01 Zeus kernel: radeon 0000:01:00.0: fence driver on ring 6 use gpu addr 0x00000000c0000c18 and cpu addr 0x00000000176b3432
Nov 15 18:49:01 Zeus kernel: radeon 0000:01:00.0: fence driver on ring 7 use gpu addr 0x00000000c0000c1c and cpu addr 0x00000000a7719c7c
Nov 15 18:49:01 Zeus kernel: radeon 0000:01:00.0: radeon: MSI limited to 32-bit
Nov 15 18:49:01 Zeus kernel: radeon 0000:01:00.0: radeon: using MSI.
Nov 15 18:49:01 Zeus kernel: [drm] radeon: irq initialized.
Nov 15 18:49:04 Zeus kernel: [drm] Radeon Display Connectors
Nov 15 18:49:04 Zeus kernel: fbcon: radeondrmfb (fb0) is primary device
Nov 15 18:49:04 Zeus kernel: [drm:si_dpm_set_power_state [radeon]] *ERROR* si_restrict_performance_levels_before_switch failed
Nov 15 18:49:04 Zeus kernel: radeon 0000:01:00.0: fb0: radeondrmfb frame buffer device
Nov 15 18:49:04 Zeus kernel: [drm:radeon_dp_link_train_cr [radeon]] *ERROR* clock recovery tried 5 times
Nov 15 18:49:04 Zeus kernel: [drm:radeon_dp_link_train_cr [radeon]] *ERROR* clock recovery failed
Nov 15 18:49:04 Zeus kernel: [drm] Initialized radeon 2.50.0 20080528 for 0000:01:00.0 on minor 0
In summary:
- The LiveUSB is just as problematic. No video signal without nomodeset.
- Booting up with the old 5.4.x kernels works. It's the 5.8.x kernel series that causes the problem.
- 5.10.x-RC kernels do not work either.
- nomodeset always works. This is not surprising since it nerfs KMS.
- The problem is only the video signal. I can ssh into the session just fine.
- When comparing the logs between a successful older kernel and a problematic newer one, the only difference is this:
Code:
Nov 15 18:49:04 Zeus kernel: [drm:radeon_dp_link_train_cr [radeon]] *ERROR* clock recovery tried 5 times
Nov 15 18:49:04 Zeus kernel: [drm:radeon_dp_link_train_cr [radeon]] *ERROR* clock recovery failed
My Web Search Fu has deserted me. All I could find with respect to these errors were these slim pickings:
http://linux-kernel.2935.n7.nabble.c...td1320976.html
https://bugs.launchpad.net/ubuntu/+s...x/+bug/1579481
https://askubuntu.com/questions/1278...ank-2nd-screen
https://askubuntu.com/questions/1286...4-lts-to-20-10
It appears that the problem bites just a few others, and is a recurring one that has some history.
Perhaps the problem is just with my Tahiti chipset‑based card. I wanted to enquire on the Forums in case any of you have found a solution before starting a bug on Launchpad.
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