Fedora: MST issues with FW13 AMD and Dell U2724DE

Community Support
1

I’m having weird issues with my new display setup (USB-C → Dell U2724DE → Dell U2724D) and the FW 13 AMD on Fedora 40: All works well when connected to the front right port (The screen acknowledges the USB3 connection), but when I connect to one of the USB4 ports, I get unpredictable results for the displays. In all cases, the USB devices are working fine and I think in all cases the displays appear working in gnome settings.

Most times, the displays stay black and I get a “no thunderbolt signal detected” message. This usually comes with dmesg showing

amdgpu 0000:c1:00.0: [drm] *ERROR* Sending link address failed with -5

Sometimes the second display (U2724D, daisy chained through DP) switches on while the first display in the chain doesn’t show anything. The error message that I’ve seen repeatedly with this issue is

amdgpu 0000:c1:00.0: [drm] *ERROR* Step 2 of creating MST payload for 0000000078e80139 failed: -5

Sometimes - rarely - both displays work after waiting for a minute or two.

Can anyone make sense of this behaviour and point me to a solution?

2

I have no solutions. But I seen very similar behavior on my 12th gen with my MST setup (1 MST Hub in dock (Synaptics VMM53xx, that seems already problematic and Intel Linux drivers do not want to use DSC), Dell U3223QE behind (other, unknown MST hub, not Synaptics), having its own MST hub from which another monitor is connected.

Works perfectly fine in Windows, with DSC where expected. Very unstable under Fedora. Ever since I got my FW.

If you do not need to use that setup on non TB/USB4 hosts, you could work around MST being problematic, by using a USB4 host port and the TB-out to use 2 separate DP connections without needing to rely on MST at all. Though I have seen other reports of there being problems with 2 DP connections through TB/USB4 for AMD under Linux.

The long term solution would be to trace the issue back to a probable driver / module and report an issue against it so it can be fixed.

3

Unfortunately I don’t have a solution to offer, but came to say that I am facing the exact same problem with the 2724DE and a DP chained secondary monitor.

Using the USB4 port the 2724DE complains about no TB signal, while the chained display works. Using a USB3.2 port everything works (though the data channel is reported as USB 2.0).

4

This is most likely not a framework problem but a linux or monitors problem. I am seeing the same behavior on my Lenovo 7 Legion running Ubuntu 24.04 with two dell 2724DE daisy chained with thunderbolt 4 (previously same happened with DP daisy chaining). I have not found for now a persistent solution. For now, what I do basically boils down to:

  • turn off second monitor
  • factory rest on first
  • turn on second monitor and experiment in a similar way.

Monitors work after factory reset up to the next sleep/turn off of computer or monitors, then the issue surfaces again. Curiously when I disable the second monitor in daisy chain, the signal is again present on the first one. After I turn ON second monitor again, the following dmesg logs appear:

dmesg log 
[ 1874.460330] pcieport 0000:00:1b.0: PME: Spurious native interrupt!
[ 1874.460384] pcieport 0000:0a:01.0: pciehp: Slot(1-1): Card present
[ 1874.460388] pcieport 0000:0a:01.0: pciehp: Slot(1-1): Link Up
[ 1875.053805] thunderbolt 0000:08:00.0: no switch exists at 301, ignoring
[ 1875.481835] pcieport 0000:0a:01.0: pciehp: Slot(1-1): No link
[ 1878.177659] pcieport 0000:00:1b.0: PME: Spurious native interrupt!
[ 1878.177713] pcieport 0000:0a:01.0: pciehp: Slot(1-1): Card present
[ 1878.177724] pcieport 0000:0a:01.0: pciehp: Slot(1-1): Link Up
[ 1878.305880] pci 0000:0c:00.0: [8086:0b26] type 01 class 0x060400 PCIe Switch Upstream Port
[ 1878.306033] pci 0000:0c:00.0: PCI bridge to [bus 00]
[ 1878.306076] pci 0000:0c:00.0:   bridge window [io  0x0000-0x0fff]
[ 1878.306097] pci 0000:0c:00.0:   bridge window [mem 0x00000000-0x000fffff]
[ 1878.306161] pci 0000:0c:00.0:   bridge window [mem 0x00000000-0x000fffff 64bit pref]
[ 1878.306230] pci 0000:0c:00.0: enabling Extended Tags
[ 1878.306897] pci 0000:0c:00.0: supports D1 D2
[ 1878.306903] pci 0000:0c:00.0: PME# supported from D0 D1 D2 D3hot D3cold
[ 1878.307363] pci 0000:0c:00.0: PTM enabled, 4ns granularity
[ 1878.308266] pci 0000:0c:00.0: Adding to iommu group 30
[ 1878.308571] pcieport 0000:0a:01.0: ASPM: current common clock configuration is inconsistent, reconfiguring
[ 1878.308708] pci 0000:0c:00.0: bridge configuration invalid ([bus 00-00]), reconfiguring
[ 1878.309189] pci 0000:0d:00.0: [8086:0b26] type 01 class 0x060400 PCIe Switch Downstream Port
[ 1878.309346] pci 0000:0d:00.0: PCI bridge to [bus 00]
[ 1878.309387] pci 0000:0d:00.0:   bridge window [io  0x0000-0x0fff]
[ 1878.309410] pci 0000:0d:00.0:   bridge window [mem 0x00000000-0x000fffff]
[ 1878.309474] pci 0000:0d:00.0:   bridge window [mem 0x00000000-0x000fffff 64bit pref]
[ 1878.309555] pci 0000:0d:00.0: enabling Extended Tags
[ 1878.310195] pci 0000:0d:00.0: supports D1 D2
[ 1878.310202] pci 0000:0d:00.0: PME# supported from D0 D1 D2 D3hot D3cold
[ 1878.311545] pci 0000:0d:00.0: Adding to iommu group 31
[ 1878.311971] pci 0000:0d:01.0: [8086:0b26] type 01 class 0x060400 PCIe Switch Downstream Port
[ 1878.312117] pci 0000:0d:01.0: PCI bridge to [bus 00]
[ 1878.312158] pci 0000:0d:01.0:   bridge window [io  0x0000-0x0fff]
[ 1878.312175] pci 0000:0d:01.0:   bridge window [mem 0x00000000-0x000fffff]
[ 1878.312259] pci 0000:0d:01.0:   bridge window [mem 0x00000000-0x000fffff 64bit pref]
[ 1878.312404] pci 0000:0d:01.0: enabling Extended Tags
[ 1878.313093] pci 0000:0d:01.0: supports D1 D2
[ 1878.313102] pci 0000:0d:01.0: PME# supported from D0 D1 D2 D3hot D3cold
[ 1878.314249] pci 0000:0d:01.0: Adding to iommu group 32
[ 1878.314663] pci 0000:0d:02.0: [8086:0b26] type 01 class 0x060400 PCIe Switch Downstream Port
[ 1878.314812] pci 0000:0d:02.0: PCI bridge to [bus 00]
[ 1878.314858] pci 0000:0d:02.0:   bridge window [io  0x0000-0x0fff]
[ 1878.314880] pci 0000:0d:02.0:   bridge window [mem 0x00000000-0x000fffff]
[ 1878.314937] pci 0000:0d:02.0:   bridge window [mem 0x00000000-0x000fffff 64bit pref]
[ 1878.315013] pci 0000:0d:02.0: enabling Extended Tags
[ 1878.315641] pci 0000:0d:02.0: supports D1 D2
[ 1878.315647] pci 0000:0d:02.0: PME# supported from D0 D1 D2 D3hot D3cold
[ 1878.316724] pci 0000:0d:02.0: Adding to iommu group 33
[ 1878.316968] pci 0000:0d:03.0: [8086:0b26] type 01 class 0x060400 PCIe Switch Downstream Port
[ 1878.317084] pci 0000:0d:03.0: PCI bridge to [bus 00]
[ 1878.317110] pci 0000:0d:03.0:   bridge window [io  0x0000-0x0fff]
[ 1878.317121] pci 0000:0d:03.0:   bridge window [mem 0x00000000-0x000fffff]
[ 1878.317167] pci 0000:0d:03.0:   bridge window [mem 0x00000000-0x000fffff 64bit pref]
[ 1878.317228] pci 0000:0d:03.0: enabling Extended Tags
[ 1878.317816] pci 0000:0d:03.0: supports D1 D2
[ 1878.317819] pci 0000:0d:03.0: PME# supported from D0 D1 D2 D3hot D3cold
[ 1878.318987] pci 0000:0d:03.0: Adding to iommu group 34
[ 1878.319303] pci 0000:0d:04.0: [8086:0b26] type 01 class 0x060400 PCIe Switch Downstream Port
[ 1878.319429] pci 0000:0d:04.0: PCI bridge to [bus 00]
[ 1878.319459] pci 0000:0d:04.0:   bridge window [io  0x0000-0x0fff]
[ 1878.319471] pci 0000:0d:04.0:   bridge window [mem 0x00000000-0x000fffff]
[ 1878.319522] pci 0000:0d:04.0:   bridge window [mem 0x00000000-0x000fffff 64bit pref]
[ 1878.319603] pci 0000:0d:04.0: enabling Extended Tags
[ 1878.320164] pci 0000:0d:04.0: supports D1 D2
[ 1878.320167] pci 0000:0d:04.0: PME# supported from D0 D1 D2 D3hot D3cold
[ 1878.321493] pci 0000:0d:04.0: Adding to iommu group 35
[ 1878.321884] pci 0000:0c:00.0: PCI bridge to [bus 0d-1c]
[ 1878.321954] pci 0000:0d:00.0: bridge configuration invalid ([bus 00-00]), reconfiguring
[ 1878.321987] pci 0000:0d:01.0: bridge configuration invalid ([bus 00-00]), reconfiguring
[ 1878.322020] pci 0000:0d:02.0: bridge configuration invalid ([bus 00-00]), reconfiguring
[ 1878.322073] pci 0000:0d:03.0: bridge configuration invalid ([bus 00-00]), reconfiguring
[ 1878.322107] pci 0000:0d:04.0: bridge configuration invalid ([bus 00-00]), reconfiguring
[ 1878.322531] pci 0000:0e:00.0: [8086:0b27] type 00 class 0x0c0330 PCIe Endpoint
[ 1878.322756] pci 0000:0e:00.0: BAR 0 [mem 0x00000000-0x0000ffff]
[ 1878.323367] pci 0000:0e:00.0: supports D1 D2
[ 1878.323368] pci 0000:0e:00.0: PME# supported from D0 D1 D2 D3hot D3cold
[ 1878.324381] pci 0000:0e:00.0: Adding to iommu group 36
[ 1878.324679] pci 0000:0d:00.0: PCI bridge to [bus 0e-1c]
[ 1878.324740] pci_bus 0000:0e: busn_res: [bus 0e-1c] end is updated to 0e
[ 1878.325106] pci 0000:0d:01.0: PCI bridge to [bus 0f-1c]
[ 1878.325164] pci_bus 0000:0f: busn_res: [bus 0f-1c] end is updated to 13
[ 1878.325464] pci 0000:0d:02.0: PCI bridge to [bus 14-1c]
[ 1878.325518] pci_bus 0000:14: busn_res: [bus 14-1c] end is updated to 18
[ 1878.325884] pci 0000:0d:03.0: PCI bridge to [bus 19-1c]
[ 1878.325937] pci_bus 0000:19: busn_res: [bus 19-1c] end is updated to 1b
[ 1878.326297] pci 0000:0d:04.0: PCI bridge to [bus 1c]
[ 1878.326351] pci_bus 0000:1c: busn_res: [bus 1c] end is updated to 1c
[ 1878.326369] pci_bus 0000:0d: busn_res: [bus 0d-1c] end is updated to 1c
[ 1878.326389] pcieport 0000:0a:01.0: Assigned bridge window [mem 0x6020100000-0x602b4fffff 64bit pref] to [bus 0c-1c] cannot fit 0x100000 required for 0000:0d:00.0 bridging to [bus 0e]
[ 1878.326394] pci 0000:0d:00.0: bridge window [mem 0x00000000-0x000fffff 64bit pref] to [bus 0e] requires relaxed alignment rules
[ 1878.326397] pcieport 0000:0a:01.0: Assigned bridge window [mem 0x80100000-0x874fffff] to [bus 0c-1c] cannot fit 0x100000 required for 0000:0d:00.0 bridging to [bus 0e]
[ 1878.326400] pci 0000:0d:00.0: bridge window [mem 0x00000000-0x000fffff] to [bus 0e] requires relaxed alignment rules
[ 1878.326402] pcieport 0000:0a:01.0: Assigned bridge window [mem 0x6020100000-0x602b4fffff 64bit pref] to [bus 0c-1c] cannot fit 0x100000 required for 0000:0d:01.0 bridging to [bus 0f-13]
[ 1878.326405] pci 0000:0d:01.0: bridge window [mem 0x00000000-0x000fffff 64bit pref] to [bus 0f-13] requires relaxed alignment rules
[ 1878.326409] pci 0000:0d:01.0: bridge window [mem 0x00100000-0x001fffff 64bit pref] to [bus 0f-13] add_size 100000 add_align 100000
[ 1878.326411] pcieport 0000:0a:01.0: Assigned bridge window [mem 0x80100000-0x874fffff] to [bus 0c-1c] cannot fit 0x100000 required for 0000:0d:01.0 bridging to [bus 0f-13]
[ 1878.326414] pci 0000:0d:01.0: bridge window [mem 0x00000000-0x000fffff] to [bus 0f-13] requires relaxed alignment rules
[ 1878.326417] pci 0000:0d:01.0: bridge window [mem 0x00100000-0x001fffff] to [bus 0f-13] add_size 100000 add_align 100000
[ 1878.326420] pcieport 0000:0a:01.0: Assigned bridge window [mem 0x6020100000-0x602b4fffff 64bit pref] to [bus 0c-1c] cannot fit 0x100000 required for 0000:0d:02.0 bridging to [bus 14-18]
[ 1878.326423] pci 0000:0d:02.0: bridge window [mem 0x00000000-0x000fffff 64bit pref] to [bus 14-18] requires relaxed alignment rules
[ 1878.326426] pci 0000:0d:02.0: bridge window [mem 0x00100000-0x001fffff 64bit pref] to [bus 14-18] add_size 100000 add_align 100000
[ 1878.326428] pcieport 0000:0a:01.0: Assigned bridge window [mem 0x80100000-0x874fffff] to [bus 0c-1c] cannot fit 0x100000 required for 0000:0d:02.0 bridging to [bus 14-18]
[ 1878.326431] pci 0000:0d:02.0: bridge window [mem 0x00000000-0x000fffff] to [bus 14-18] requires relaxed alignment rules
[ 1878.326433] pci 0000:0d:02.0: bridge window [mem 0x00100000-0x001fffff] to [bus 14-18] add_size 100000 add_align 100000
[ 1878.326436] pcieport 0000:0a:01.0: Assigned bridge window [mem 0x6020100000-0x602b4fffff 64bit pref] to [bus 0c-1c] cannot fit 0x100000 required for 0000:0d:03.0 bridging to [bus 19-1b]
[ 1878.326439] pci 0000:0d:03.0: bridge window [mem 0x00000000-0x000fffff 64bit pref] to [bus 19-1b] requires relaxed alignment rules
[ 1878.326442] pci 0000:0d:03.0: bridge window [mem 0x00100000-0x001fffff 64bit pref] to [bus 19-1b] add_size 100000 add_align 100000
[ 1878.326445] pcieport 0000:0a:01.0: Assigned bridge window [mem 0x80100000-0x874fffff] to [bus 0c-1c] cannot fit 0x100000 required for 0000:0d:03.0 bridging to [bus 19-1b]
[ 1878.326448] pci 0000:0d:03.0: bridge window [mem 0x00000000-0x000fffff] to [bus 19-1b] requires relaxed alignment rules
[ 1878.326450] pci 0000:0d:03.0: bridge window [mem 0x00100000-0x001fffff] to [bus 19-1b] add_size 100000 add_align 100000
[ 1878.326453] pcieport 0000:0a:01.0: Assigned bridge window [mem 0x6020100000-0x602b4fffff 64bit pref] to [bus 0c-1c] cannot fit 0x100000 required for 0000:0d:04.0 bridging to [bus 1c]
[ 1878.326456] pci 0000:0d:04.0: bridge window [mem 0x00000000-0x000fffff 64bit pref] to [bus 1c] requires relaxed alignment rules
[ 1878.326458] pcieport 0000:0a:01.0: Assigned bridge window [mem 0x80100000-0x874fffff] to [bus 0c-1c] cannot fit 0x100000 required for 0000:0d:04.0 bridging to [bus 1c]
[ 1878.326461] pci 0000:0d:04.0: bridge window [mem 0x00000000-0x000fffff] to [bus 1c] requires relaxed alignment rules
[ 1878.326466] pci 0000:0c:00.0: bridge window [mem 0x00100000-0x005fffff 64bit pref] to [bus 0d-1c] add_size 300000 add_align 100000
[ 1878.326469] pci 0000:0c:00.0: bridge window [mem 0x00100000-0x005fffff] to [bus 0d-1c] add_size 300000 add_align 100000
[ 1878.326476] pcieport 0000:0a:01.0: bridge window [io  size 0x5000]: can't assign; no space
[ 1878.326479] pcieport 0000:0a:01.0: bridge window [io  size 0x5000]: failed to assign
[ 1878.326483] pci 0000:0c:00.0: bridge window [mem 0x80100000-0x874fffff]: assigned
[ 1878.326486] pci 0000:0c:00.0: bridge window [mem 0x6020100000-0x602b4fffff 64bit pref]: assigned
[ 1878.326488] pci 0000:0c:00.0: bridge window [io  size 0x5000]: can't assign; no space
[ 1878.326490] pci 0000:0c:00.0: bridge window [io  size 0x5000]: failed to assign
[ 1878.326493] pci 0000:0d:00.0: bridge window [mem 0x80100000-0x801fffff]: assigned
[ 1878.326496] pci 0000:0d:00.0: bridge window [mem 0x6020100000-0x60201fffff 64bit pref]: assigned
[ 1878.326498] pci 0000:0d:01.0: bridge window [mem 0x80200000-0x827fffff]: assigned
[ 1878.326500] pci 0000:0d:01.0: bridge window [mem 0x6020200000-0x6023cfffff 64bit pref]: assigned
[ 1878.326502] pci 0000:0d:02.0: bridge window [mem 0x82800000-0x84dfffff]: assigned
[ 1878.326504] pci 0000:0d:02.0: bridge window [mem 0x6023d00000-0x60277fffff 64bit pref]: assigned
[ 1878.326506] pci 0000:0d:03.0: bridge window [mem 0x84e00000-0x873fffff]: assigned
[ 1878.326508] pci 0000:0d:03.0: bridge window [mem 0x6027800000-0x602b2fffff 64bit pref]: assigned
[ 1878.326510] pci 0000:0d:04.0: bridge window [mem 0x87400000-0x874fffff]: assigned
[ 1878.326513] pci 0000:0d:04.0: bridge window [mem 0x602b300000-0x602b3fffff 64bit pref]: assigned
[ 1878.326515] pci 0000:0d:00.0: bridge window [io  size 0x1000]: can't assign; no space
[ 1878.326516] pci 0000:0d:00.0: bridge window [io  size 0x1000]: failed to assign
[ 1878.326518] pci 0000:0d:01.0: bridge window [io  size 0x1000]: can't assign; no space
[ 1878.326520] pci 0000:0d:01.0: bridge window [io  size 0x1000]: failed to assign
[ 1878.326521] pci 0000:0d:02.0: bridge window [io  size 0x1000]: can't assign; no space
[ 1878.326523] pci 0000:0d:02.0: bridge window [io  size 0x1000]: failed to assign
[ 1878.326525] pci 0000:0d:03.0: bridge window [io  size 0x1000]: can't assign; no space
[ 1878.326527] pci 0000:0d:03.0: bridge window [io  size 0x1000]: failed to assign
[ 1878.326528] pci 0000:0d:04.0: bridge window [io  size 0x1000]: can't assign; no space
[ 1878.326530] pci 0000:0d:04.0: bridge window [io  size 0x1000]: failed to assign
[ 1878.326533] pci 0000:0e:00.0: BAR 0 [mem 0x80100000-0x8010ffff]: assigned
[ 1878.326549] pci 0000:0d:00.0: PCI bridge to [bus 0e]
[ 1878.326567] pci 0000:0d:00.0:   bridge window [mem 0x80100000-0x801fffff]
[ 1878.326585] pci 0000:0d:00.0:   bridge window [mem 0x6020100000-0x60201fffff 64bit pref]
[ 1878.326612] pci 0000:0d:01.0: PCI bridge to [bus 0f-13]
[ 1878.326630] pci 0000:0d:01.0:   bridge window [mem 0x80200000-0x827fffff]
[ 1878.326642] pci 0000:0d:01.0:   bridge window [mem 0x6020200000-0x6023cfffff 64bit pref]
[ 1878.326663] pci 0000:0d:02.0: PCI bridge to [bus 14-18]
[ 1878.326681] pci 0000:0d:02.0:   bridge window [mem 0x82800000-0x84dfffff]
[ 1878.326693] pci 0000:0d:02.0:   bridge window [mem 0x6023d00000-0x60277fffff 64bit pref]
[ 1878.326715] pci 0000:0d:03.0: PCI bridge to [bus 19-1b]
[ 1878.326733] pci 0000:0d:03.0:   bridge window [mem 0x84e00000-0x873fffff]
[ 1878.326745] pci 0000:0d:03.0:   bridge window [mem 0x6027800000-0x602b2fffff 64bit pref]
[ 1878.326767] pci 0000:0d:04.0: PCI bridge to [bus 1c]
[ 1878.326783] pci 0000:0d:04.0:   bridge window [mem 0x87400000-0x874fffff]
[ 1878.326796] pci 0000:0d:04.0:   bridge window [mem 0x602b300000-0x602b3fffff 64bit pref]
[ 1878.326818] pci 0000:0c:00.0: PCI bridge to [bus 0d-1c]
[ 1878.326835] pci 0000:0c:00.0:   bridge window [mem 0x80100000-0x874fffff]
[ 1878.326847] pci 0000:0c:00.0:   bridge window [mem 0x6020100000-0x602b4fffff 64bit pref]
[ 1878.326869] pcieport 0000:0a:01.0: PCI bridge to [bus 0c-1c]
[ 1878.326882] pcieport 0000:0a:01.0:   bridge window [mem 0x80100000-0x874fffff]
[ 1878.326892] pcieport 0000:0a:01.0:   bridge window [mem 0x6020100000-0x602b4fffff 64bit pref]
[ 1878.326909] PCI: No. 2 try to assign unassigned res
[ 1878.326916] pcieport 0000:0a:01.0: bridge window [io  size 0x5000]: can't assign; no space
[ 1878.326918] pcieport 0000:0a:01.0: bridge window [io  size 0x5000]: failed to assign
[ 1878.326921] pci 0000:0c:00.0: bridge window [io  size 0x5000]: can't assign; no space
[ 1878.326923] pci 0000:0c:00.0: bridge window [io  size 0x5000]: failed to assign
[ 1878.326926] pci 0000:0d:00.0: bridge window [io  size 0x1000]: can't assign; no space
[ 1878.326928] pci 0000:0d:00.0: bridge window [io  size 0x1000]: failed to assign
[ 1878.326930] pci 0000:0d:01.0: bridge window [io  size 0x1000]: can't assign; no space
[ 1878.326932] pci 0000:0d:01.0: bridge window [io  size 0x1000]: failed to assign
[ 1878.326934] pci 0000:0d:02.0: bridge window [io  size 0x1000]: can't assign; no space
[ 1878.326936] pci 0000:0d:02.0: bridge window [io  size 0x1000]: failed to assign
[ 1878.326938] pci 0000:0d:03.0: bridge window [io  size 0x1000]: can't assign; no space
[ 1878.326940] pci 0000:0d:03.0: bridge window [io  size 0x1000]: failed to assign
[ 1878.326941] pci 0000:0d:04.0: bridge window [io  size 0x1000]: can't assign; no space
[ 1878.326943] pci 0000:0d:04.0: bridge window [io  size 0x1000]: failed to assign
[ 1878.326946] pci 0000:0d:00.0: PCI bridge to [bus 0e]
[ 1878.326966] pci 0000:0d:00.0:   bridge window [mem 0x80100000-0x801fffff]
[ 1878.326979] pci 0000:0d:00.0:   bridge window [mem 0x6020100000-0x60201fffff 64bit pref]
[ 1878.327001] pci 0000:0d:01.0: PCI bridge to [bus 0f-13]
[ 1878.327018] pci 0000:0d:01.0:   bridge window [mem 0x80200000-0x827fffff]
[ 1878.327031] pci 0000:0d:01.0:   bridge window [mem 0x6020200000-0x6023cfffff 64bit pref]
[ 1878.327053] pci 0000:0d:02.0: PCI bridge to [bus 14-18]
[ 1878.327070] pci 0000:0d:02.0:   bridge window [mem 0x82800000-0x84dfffff]
[ 1878.327106] pci 0000:0d:02.0:   bridge window [mem 0x6023d00000-0x60277fffff 64bit pref]
[ 1878.327143] pci 0000:0d:03.0: PCI bridge to [bus 19-1b]
[ 1878.327173] pci 0000:0d:03.0:   bridge window [mem 0x84e00000-0x873fffff]
[ 1878.327197] pci 0000:0d:03.0:   bridge window [mem 0x6027800000-0x602b2fffff 64bit pref]
[ 1878.327233] pci 0000:0d:04.0: PCI bridge to [bus 1c]
[ 1878.327264] pci 0000:0d:04.0:   bridge window [mem 0x87400000-0x874fffff]
[ 1878.327288] pci 0000:0d:04.0:   bridge window [mem 0x602b300000-0x602b3fffff 64bit pref]
[ 1878.327324] pci 0000:0c:00.0: PCI bridge to [bus 0d-1c]
[ 1878.327354] pci 0000:0c:00.0:   bridge window [mem 0x80100000-0x874fffff]
[ 1878.327379] pci 0000:0c:00.0:   bridge window [mem 0x6020100000-0x602b4fffff 64bit pref]
[ 1878.327415] pcieport 0000:0a:01.0: PCI bridge to [bus 0c-1c]
[ 1878.327441] pcieport 0000:0a:01.0:   bridge window [mem 0x80100000-0x874fffff]
[ 1878.327462] pcieport 0000:0a:01.0:   bridge window [mem 0x6020100000-0x602b4fffff 64bit pref]
[ 1878.327608] pcieport 0000:0c:00.0: enabling device (0000 -> 0002)
[ 1878.328673] pcieport 0000:0d:00.0: enabling device (0000 -> 0002)
[ 1878.329379] pcieport 0000:0d:01.0: enabling device (0000 -> 0002)
[ 1878.329862] pcieport 0000:0d:01.0: pciehp: Slot #1 AttnBtn- PwrCtrl- MRL- AttnInd- PwrInd- HotPlug+ Surprise+ Interlock- NoCompl+ IbPresDis- LLActRep+
[ 1878.330523] pcieport 0000:0d:02.0: enabling device (0000 -> 0002)
[ 1878.330972] pcieport 0000:0d:02.0: pciehp: Slot #2 AttnBtn- PwrCtrl- MRL- AttnInd- PwrInd- HotPlug+ Surprise+ Interlock- NoCompl+ IbPresDis- LLActRep+
[ 1878.331576] pcieport 0000:0d:03.0: enabling device (0000 -> 0002)
[ 1878.332173] pcieport 0000:0d:03.0: pciehp: Slot #3 AttnBtn- PwrCtrl- MRL- AttnInd- PwrInd- HotPlug+ Surprise+ Interlock- NoCompl+ IbPresDis- LLActRep+
[ 1878.332781] pcieport 0000:0d:04.0: enabling device (0000 -> 0002)
[ 1878.334110] pci 0000:0e:00.0: enabling device (0000 -> 0002)
[ 1878.334724] xhci_hcd 0000:0e:00.0: xHCI Host Controller
[ 1878.334746] xhci_hcd 0000:0e:00.0: new USB bus registered, assigned bus number 9
[ 1878.336313] xhci_hcd 0000:0e:00.0: hcc params 0x20007fc1 hci version 0x110 quirks 0x0000000000009810
[ 1878.337673] xhci_hcd 0000:0e:00.0: xHCI Host Controller
[ 1878.337683] xhci_hcd 0000:0e:00.0: new USB bus registered, assigned bus number 10
[ 1878.337692] xhci_hcd 0000:0e:00.0: Host supports USB 3.1 Enhanced SuperSpeed
[ 1878.337783] usb usb9: New USB device found, idVendor=1d6b, idProduct=0002, bcdDevice= 6.14
[ 1878.337787] usb usb9: New USB device strings: Mfr=3, Product=2, SerialNumber=1
[ 1878.337789] usb usb9: Product: xHCI Host Controller
[ 1878.337791] usb usb9: Manufacturer: Linux 6.14.0-33-generic xhci-hcd
[ 1878.337793] usb usb9: SerialNumber: 0000:0e:00.0
[ 1878.338266] hub 9-0:1.0: USB hub found
[ 1878.338296] hub 9-0:1.0: 2 ports detected
[ 1878.339056] usb usb10: New USB device found, idVendor=1d6b, idProduct=0003, bcdDevice= 6.14
[ 1878.339060] usb usb10: New USB device strings: Mfr=3, Product=2, SerialNumber=1
[ 1878.339062] usb usb10: Product: xHCI Host Controller
[ 1878.339064] usb usb10: Manufacturer: Linux 6.14.0-33-generic xhci-hcd
[ 1878.339065] usb usb10: SerialNumber: 0000:0e:00.0
[ 1878.339540] hub 10-0:1.0: USB hub found
[ 1878.339564] hub 10-0:1.0: 2 ports detected
[ 1878.532180] thunderbolt 0-301: new device found, vendor=0xd4 device=0xc045
[ 1878.532184] thunderbolt 0-301: DELL U2724DE
[ 1878.577668] usb 9-1: new high-speed USB device number 2 using xhci_hcd
[ 1878.702065] usb 9-1: New USB device found, idVendor=1d5c, idProduct=5801, bcdDevice= 1.01
[ 1878.702083] usb 9-1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[ 1878.702090] usb 9-1: Product: USB2.0 Hub
[ 1878.702096] usb 9-1: Manufacturer: Fresco Logic, Inc.
[ 1878.704357] hub 9-1:1.0: USB hub found
[ 1878.704446] hub 9-1:1.0: 6 ports detected
[ 1878.813870] usb 10-1: new SuperSpeed Plus Gen 2x1 USB device number 2 using xhci_hcd
[ 1878.826640] usb 10-1: New USB device found, idVendor=8087, idProduct=0b40, bcdDevice=12.34
[ 1878.826659] usb 10-1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[ 1878.826666] usb 10-1: Product: USB3.0 Hub
[ 1878.826672] usb 10-1: Manufacturer: Intel Corporation.
[ 1878.829528] hub 10-1:1.0: USB hub found
[ 1878.829664] hub 10-1:1.0: 4 ports detected
[ 1879.242621] usb 9-1.4: new high-speed USB device number 3 using xhci_hcd
[ 1879.331400] usb 9-1.4: New USB device found, idVendor=0bda, idProduct=5483, bcdDevice= 1.07
[ 1879.331405] usb 9-1.4: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[ 1879.331406] usb 9-1.4: Product: 4-Port USB 2.0 Hub
[ 1879.331407] usb 9-1.4: Manufacturer: Generic
[ 1879.334148] hub 9-1.4:1.0: USB hub found
[ 1879.334392] hub 9-1.4:1.0: 5 ports detected
[ 1879.391728] usb 10-1.4: new SuperSpeed Plus Gen 2x1 USB device number 3 using xhci_hcd
[ 1879.406035] usb 10-1.4: New USB device found, idVendor=0bda, idProduct=0483, bcdDevice= 1.07
[ 1879.406039] usb 10-1.4: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[ 1879.406041] usb 10-1.4: Product: 4-Port USB 3.0 Hub
[ 1879.406043] usb 10-1.4: Manufacturer: Generic
[ 1879.410088] hub 10-1.4:1.0: USB hub found
[ 1879.410372] hub 10-1.4:1.0: 4 ports detected
[ 1879.620544] usb 9-1.4.1: new high-speed USB device number 4 using xhci_hcd
[ 1879.710489] usb 9-1.4.1: New USB device found, idVendor=0bda, idProduct=5483, bcdDevice= 2.09
[ 1879.710494] usb 9-1.4.1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[ 1879.710495] usb 9-1.4.1: Product: 4-Port USB 2.0 Hub
[ 1879.710496] usb 9-1.4.1: Manufacturer: Generic
[ 1879.713969] hub 9-1.4.1:1.0: USB hub found
[ 1879.714185] hub 9-1.4.1:1.0: 4 ports detected
[ 1879.772146] usb 10-1.4.1: new SuperSpeed Plus Gen 2x1 USB device number 4 using xhci_hcd
[ 1879.786146] usb 10-1.4.1: New USB device found, idVendor=0bda, idProduct=0483, bcdDevice= 2.09
[ 1879.786151] usb 10-1.4.1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[ 1879.786152] usb 10-1.4.1: Product: 4-Port USB 3.0 Hub
[ 1879.786153] usb 10-1.4.1: Manufacturer: Generic
[ 1879.790681] hub 10-1.4.1:1.0: USB hub found
[ 1879.791243] hub 10-1.4.1:1.0: 4 ports detected
[ 1879.859550] usb 9-1.4.5: new high-speed USB device number 5 using xhci_hcd
[ 1879.947639] usb 9-1.4.5: New USB device found, idVendor=0bda, idProduct=1100, bcdDevice= 1.01
[ 1879.947644] usb 9-1.4.5: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 1879.947645] usb 9-1.4.5: Product: USB2.0 HID
[ 1879.947646] usb 9-1.4.5: Manufacturer: Realtek
[ 1879.947647] usb 9-1.4.5: SerialNumber: 0123456789ABCDEF
[ 1879.953037] hid-generic 0003:0BDA:1100.0013: hiddev3,hidraw5: USB HID v1.11 Device [Realtek USB2.0 HID] on usb-0000:0e:00.0-1.4.5/input0
[ 1880.010681] usb 10-1.4.2: new SuperSpeed USB device number 5 using xhci_hcd
[ 1880.022535] usb 10-1.4.2: New USB device found, idVendor=0bda, idProduct=8156, bcdDevice=31.10
[ 1880.022560] usb 10-1.4.2: New USB device strings: Mfr=1, Product=2, SerialNumber=6
[ 1880.022562] usb 10-1.4.2: Product: USB 10/100/1G/2.5G LAN
[ 1880.022564] usb 10-1.4.2: Manufacturer: Realtek
[ 1880.022566] usb 10-1.4.2: SerialNumber: 0113000001
[ 1880.094300] r8152-cfgselector 10-1.4.2: reset SuperSpeed USB device number 5 using xhci_hcd
[ 1880.172602] r8152 10-1.4.2:1.0 eth0: v1.12.13
[ 1880.244366] r8152 10-1.4.2:1.0 enx109819529f87: renamed from eth0

System info:

$ inxi -SGC
System:
  Host: *** Kernel: 6.14.0-33-generic arch: x86_64 bits: 64
  Desktop: GNOME v: 46.0 Distro: Kubuntu 24.04.3 LTS (Noble Numbat)
CPU:
  Info: 6-core model: Intel Core i7-10750H bits: 64 type: MT MCP cache:
    L2: 1.5 MiB
  Speed (MHz): avg: 800 min/max: 800/5000 cores: 1: 800 2: 800 3: 800 4: 800
    5: 800 6: 800 7: 800 8: 800 9: 800 10: 800 11: 800 12: 800
Graphics:
  Device-1: Intel CometLake-H GT2 [UHD Graphics] driver: i915 v: kernel
  Device-2: NVIDIA TU104BM [GeForce RTX 2070 SUPER Mobile / Max-Q]
    driver: nvidia v: 580.95.05
  Device-3: Syntek Integrated Camera driver: uvcvideo type: USB
  Display: x11 server: X.Org v: 21.1.11 with: Xwayland v: 23.2.6 driver: X:
    loaded: modesetting,nvidia unloaded: fbdev,nouveau,vesa dri: iris gpu: i915
    resolution: 1: 2560x1440~120Hz 2: 2560x1440~120Hz 3: 1920x1080~144Hz
  API: EGL v: 1.5 drivers: iris,nouveau,nvidia,swrast
    platforms: gbm,x11,surfaceless,device
  API: OpenGL v: 4.6.0 compat-v: 4.5 vendor: intel mesa
    v: 25.0.7-0ubuntu0.24.04.2 renderer: Mesa Intel UHD Graphics (CML GT2)
  API: Vulkan v: 1.3.275 drivers: N/A surfaces: xcb,xlib

Remember that wit Dell 2724DE monitor you need daisy chain to be set up between proper ports when using TB4 (notebook → TB upstream (90W) primary monitor, primary TB downstream (bolt with arrow) → TB upstream (90W) secondary monitor). Dell video about daisy chain, and monitor spec (see ports). DP daisy chain won’t make your secondary monitor’s hub visible. btw (and on my ubuntu the IDs of monitors are inverted, i.e. first monitor in the chain is reoprted as 3rd).

This is beyond my area of expertise, so I employed AI to help me diagnose the problem by reading the dmesg log:

AI response

Nice — that’s a very telling log dump.
You’re running into a Thunderbolt PCIe resource exhaustion / reallocation failure problem that breaks display enumeration during Thunderbolt daisy chaining.

Let’s unpack the key lines and what they mean. :backhand_index_pointing_down:

:puzzle_piece: What’s happening

When you daisy-chain two Thunderbolt 4 monitors, each one effectively contains a Thunderbolt switch (PCIe bridges + DP tunneling endpoints).
Linux enumerates them as cascaded PCIe bridges and endpoints under the Thunderbolt host controller.

When you power on the second monitor, the kernel log shows:

thunderbolt 0000:08:00.0: no switch exists at 301, ignoring

:right_arrow: The Thunderbolt controller expected to see a switch but didn’t get a proper enumeration response — typical when PCIe bus resource assignment fails.

Then:

bridge configuration invalid ([bus 00-00]), reconfiguring
...
cannot fit 0x100000 required ... requires relaxed alignment rules
...
bridge window [io size 0x1000]: can't assign; no space

:right_arrow: PCIe bridge window assignment failed — your system ran out of address space (I/O or memory ranges) for all the downstream bridges that Thunderbolt created.
This means the kernel cannot assign proper memory windows for the daisy-chained device hierarchy, so the display endpoints never come online.

This is usually triggered when:

  • Firmware (BIOS/UEFI) allocates too little address space to the Thunderbolt PCIe root port.
  • ASPM or hotplug misconfiguration causes partial re-enumeration.
  • ACPI or IOMMU restricts resource remapping.
  • You connect multiple DP-tunneling monitors through Thunderbolt (each adds multiple downstream ports).

:collision: Why “no signal” occurs

Thunderbolt monitors rely on DisplayPort tunneling through the PCIe fabric.
If PCIe enumeration fails, the DP tunnels are never set up, so:

  • The GPU doesn’t see the monitor as connected.
  • Both monitors may blank because the Thunderbolt link resets and renegotiates (they temporarily lose their DP stream).

This explains:

“After turning on the second monitor, both go dark.”

:compass: How to fix or work around it

1. Update firmware

  • Update BIOS/UEFI and Thunderbolt NVM firmware.

  • Check for updates for your laptop/mainboard (Intel’s TB controllers rely heavily on firmware allocation tables).

  • On Linux, you can check current firmware with:

    boltctl list
sudo fwupdmgr get-updates

2. Enable large BAR / PCIe resource allocation

Some BIOSes have options like:

  • “Above 4G decoding”
  • “Re-size BAR support”
  • “PCIe resource allocation: Large”

:white_check_mark: Enable both Above 4G Decoding and Resizable BAR Support if available.
They allow larger address windows for Thunderbolt chains.

3. Avoid daisy chaining — test single connection

Try connecting each monitor directly to a Thunderbolt port on your laptop/PC.
If both work individually, the issue is definitely resource exhaustion in the Thunderbolt chain, not a GPU driver or display protocol problem.

4. Kernel parameters to relax PCI resource assignment

Sometimes Linux can recover if you let it reassign PCI spaces:
Add to your kernel command line in /etc/default/grub:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash pci=realloc"

Then:

sudo update-grub
sudo reboot

This lets Linux override BIOS-assigned windows and fix the “can’t assign; no space” messages.

You can also try:

pci=assign-busses,realloc,pcie_bus_safe

or

pci=assign-busses,realloc,pcie_bus_perf

5. Thunderbolt power / link management

You may also see spurious interrupts and ASPM inconsistencies:

ASPM: current common clock configuration is inconsistent, reconfiguring

Try disabling ASPM temporarily:

pcie_aspm=off

(to check if power management is interfering).

6. Use bolt / thunderboltctl to check device authorization

If secure connect mode is on, the second monitor might not be authorized:

boltctl
boltctl authorize <uuid>

:brain: TL;DR Diagnosis Summary

Symptom Meaning
no switch exists at 301 Daisy-chain device failed to enumerate
bridge configuration invalid PCIe bridge bus numbers out of range
can't assign; no space BIOS didn’t allocate enough address space
ASPM inconsistent PCIe power management state flapping
Both monitors dark DP tunnel negotiation failed after TB re-enum

:white_check_mark: Main cause: BIOS/firmware Thunderbolt PCIe window exhaustion during daisy-chained monitor hotplug.
:toolbox: Fix: enable Above 4G decoding, use pci=realloc, update firmware, or connect monitors directly.

5

I have weird issues with a dell windows machine and this daisy chained monitor combination aswell, except these at least work after a reconnect and a windows warning message. It very much seems to be a 2724DE issue, but it’s possible to handle it more gracefully. I’m still eagerly installing firmware upgrades to the monitors to see if they fix the issue - no luck so far.