[Bug 2058333] Re: daisy chained thunderbolt devices not working at reboot on AMD strix platforms

Noble Ubuntu-6.8.0-38.38 ships with v6.8.8 stable fixes.

** Changed in: linux (Ubuntu Noble)
Status: Triaged => Fix Released

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https://bugs.launchpad.net/bugs/2058333

Title:
daisy chained thunderbolt devices not working at reboot on AMD strix
platforms

Status in HWE Next:
New
Status in linux package in Ubuntu:
Fix Released
Status in linux-oem-6.8 package in Ubuntu:
Invalid
Status in linux source package in Noble:
Fix Released
Status in linux-oem-6.8 source package in Noble:
Fix Released

Bug description:
[SRU Justification]

[Impact]

Devices on PCIe bus on some AMD based systems may not function
normally.

Boot firmware (typically BIOS) might have created tunnels of its own.
The tunnel configuration that it does might be sub-optimal. For
instance it may only support HBR2 monitors so the DisplayPort tunnels
it created may limit Linux graphics drivers. In addition there is an
issue on some AMD based systems where the BIOS does not allocate
enough PCIe resources for future topology extension.

[Fix]

4 commits already in upstream linux repo that resets USB4 v1 routers
in addition to already reset v2 routes to align the behavior with
Windows Connection Manager.

[Test Case]

On affected platforms with monitor connected across reboots, the DUT
reboots into linux with blank screen. This should turn it back to
normal as expected.

[Where problems could occur]

No. The reset triggers Linux to re-allocate necessary resources for
its own, and this is what Windows does, too.

[Other Info]

While this is in v6.9-rc1 and backported to stable at v6.8.8, Noble
and oem-6.8 are nominated.

========== original but report ==========

Boot firmware (typically BIOS) might have created tunnels of its own.
The tunnel configuration that it does might be sub-optimal. For
instance it may only support HBR2 monitors so the DisplayPort tunnels
it created may limit Linux graphics drivers. In addition there is an
issue on some AMD based systems where the BIOS does not allocate
enough PCIe resources for future topology extension. By resetting the
USB4 topology the PCIe links will be reset as well allowing Linux to
re-allocate.

This aligns the behavior with Windows Connection Manager.

Fixes merged to linus tree for v6.9-rc1:
* 59a54c5f3dbde thunderbolt: Reset topology created by the boot firmware
* ec8162b3f0683 thunderbolt: Make tb_switch_reset() support Thunderbolt 2, 3 and USB4 routers
* b35c1d7b11da8 thunderbolt: Introduce tb_path_deactivate_hop()
* 01da6b99d49f6 thunderbolt: Introduce tb_port_reset()

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