Re: thunderbolt: AMD Phoenix USB4 host advertises Gen3 Support=0 in SB LINK_CONF with TB5 device, link stuck at Gen2

[James R Taylor <jrtaylor11@gmail.com>]

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Hi Mika,

On Mon, Nov 09, 2026 at 03:20:41PM +0100, Mika Westerberg wrote:
> Please drop thunderbolt.host_reset=0 and pcie_aspm=off. The later disables
> much more than just ASPM so it may affect everything. Once you have done
> that please take another dmesg (and check also the link registers via
> tbdump).

Done. I rebooted with both parameters removed. The only addition is
thunderbolt.dyndbg=+p so the full debug output is in the log:

  nohibernate root=fstab loglevel=4 lsm=landlock,yama,bpf usb-storage.quirks=0bc2:3343:u thunderbolt.dyndbg=+p

The result is the same as before: the link still comes up as TBT at
10 Gb/s x2 (the dmesg has "2: link: TBT" and "current link speed
10.0 Gb/s"), and the lane adapter registers are identical to my
previous dump. The host lane adapter targets Gen 3, the DEG2 targets
Gen 4, and both report Current Link Speed = Gen 2, x2.

The full dmesg from this boot is attached (gzipped). The tbdump output
is below.

    # cmdline: initrd=\EFI\nixos\c18phgd1m2qpc2g72pz14fg9h9i38j6w-initrd-linux-7.2.15-initrd.efi init=/nix/store/x1jyvpbgdhl6a91iysmbr5wisgi0sghd-nixos-system-nyx-26.11.20261106.4fe25e1/init usb-storage.quirks=0bc2:3343:u nohibernate root=fstab loglevel=4 lsm=landlock,yama,bpf thunderbolt.dyndbg=+p
    # 1-2 rx=10.0 Gb/s x2 tx=10.0 Gb/s x2
    # usb4_port link: none tbt tbt none none none

    $ tbdump -d 1 -r 0 -a 2 -N 2 -vv LANE_ADP_CS_0
    0x0080 0x003c01c0 0b00000000 00111100 00000001 11000000 .<.. LANE_ADP_CS_0
      [00:07]       0xc0 Next Capability Pointer
      [08:15]        0x1 Capability ID
      [16:19]        0xc Supported Link Speeds
      [20:21]        0x3 Supported Link Widths (SLW)
      [22:23]        0x0 Gen 4 Asymmetric Support (G4AS)
      [26:26]        0x0 CL0s Support
      [27:27]        0x0 CL1 Support
      [28:28]        0x0 CL2 Support
    0x0081 0x4828003c 0b01001000 00101000 00000000 00111100 H(.< LANE_ADP_CS_1
      [00:03]        0xc Target Link Speed → Router shall attempt Gen 3 speed
      [04:05]        0x3 Target Link Width → Establish a Symmetric Link
      [06:07]        0x0 Target Asymmetric Link → Establish Symmetric Link
      [10:10]        0x0 CL0s Enable
      [11:11]        0x0 CL1 Enable
      [12:12]        0x0 CL2 Enable
      [14:14]        0x0 Lane Disable (LD)
      [15:15]        0x0 Lane Bonding (LB)
      [16:19]        0x8 Current Link Speed → Gen 2
      [20:25]        0x2 Negotiated Link Width → Symmetric Link (x2)
      [26:29]        0x2 Adapter State → CL0
      [30:30]        0x1 PM Secondary (PMS)

    $ tbdump -d 1 -r 2 -a 1 -N 2 -vv LANE_ADP_CS_0
    0x0036 0x0cfe01c0 0b00001100 11111110 00000001 11000000 .... LANE_ADP_CS_0
      [00:07]       0xc0 Next Capability Pointer
      [08:15]        0x1 Capability ID
      [16:19]        0xe Supported Link Speeds
      [20:21]        0x3 Supported Link Widths (SLW)
      [22:23]        0x3 Gen 4 Asymmetric Support (G4AS)
      [26:26]        0x1 CL0s Support
      [27:27]        0x1 CL1 Support
      [28:28]        0x0 CL2 Support
    0x0037 0x4828003e 0b01001000 00101000 00000000 00111110 H(.> LANE_ADP_CS_1
      [00:03]        0xe Target Link Speed → Router shall attempt Gen 4 speed
      [04:05]        0x3 Target Link Width → Establish a Symmetric Link
      [06:07]        0x0 Target Asymmetric Link → Establish Symmetric Link
      [10:10]        0x0 CL0s Enable
      [11:11]        0x0 CL1 Enable
      [12:12]        0x0 CL2 Enable
      [14:14]        0x0 Lane Disable (LD)
      [15:15]        0x0 Lane Bonding (LB)
      [16:19]        0x8 Current Link Speed → Gen 2
      [20:25]        0x2 Negotiated Link Width → Symmetric Link (x2)
      [26:29]        0x2 Adapter State → CL0
      [30:30]        0x1 PM Secondary (PMS)

    $ tbdump -d 1 -r 2 -a 2 -N 2 -vv LANE_ADP_CS_0
    0x0036 0x0cfe0100 0b00001100 11111110 00000001 00000000 .... LANE_ADP_CS_0
      [00:07]        0x0 Next Capability Pointer
      [08:15]        0x1 Capability ID
      [16:19]        0xe Supported Link Speeds
      [20:21]        0x3 Supported Link Widths (SLW)
      [22:23]        0x3 Gen 4 Asymmetric Support (G4AS)
      [26:26]        0x1 CL0s Support
      [27:27]        0x1 CL1 Support
      [28:28]        0x0 CL2 Support
    0x0037 0x4828003e 0b01001000 00101000 00000000 00111110 H(.> LANE_ADP_CS_1
      [00:03]        0xe Target Link Speed → Router shall attempt Gen 4 speed
      [04:05]        0x3 Target Link Width → Establish a Symmetric Link
      [06:07]        0x0 Target Asymmetric Link → Establish Symmetric Link
      [10:10]        0x0 CL0s Enable
      [11:11]        0x0 CL1 Enable
      [12:12]        0x0 CL2 Enable
      [14:14]        0x0 Lane Disable (LD)
      [15:15]        0x0 Lane Bonding (LB)
      [16:19]        0x8 Current Link Speed → Gen 2
      [20:25]        0x2 Negotiated Link Width → Symmetric Link (x2)
      [26:29]        0x2 Adapter State → CL0
      [30:30]        0x1 PM Secondary (PMS)

    $ tbadapters -d 1 -r 0
     1: Host Interface (upstream)     Enabled
     2: Lane 0                        CL0
     3: Lane 0                        CL0
     4: USB 3 Down                    Disabled
     5: PCIe Down                     L0
     6: DisplayPort IN                Disabled
     7: DisplayPort IN                Disabled

    $ tbadapters -d 1 -r 2
     1: Lane 0 (upstream)             CL0
     2: Lane 1                        CL0
     3: Lane 0                        CLd
     4: Lane 1                        CLd
     5: Lane 0                        CLd
     6: Lane 1                        CLd
     7: Lane 0                        CLd
     8: Lane 1                        CLd
     9: PCIe Up                       L0
    10: PCIe Down                     Disabled
    11: DisplayPort OUT               Disabled
    12: DisplayPort OUT               Disabled
    13: Not implemented
    14: Not implemented
    15: Not implemented
    16: Not implemented
    17: PCIe Down                     Disabled
    18: PCIe Down                     Disabled
    19: DisplayPort OUT               Disabled
    20: USB 3 Up                      Disabled
    21: USB 3 Down                    Disabled
    22: USB 3 Down                    Disabled
    23: USB 3 Down                    Disabled

Thanks,
James

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