[Bug 218795] USB4 / Thunderbolt + AMD: unstable and slow link (many uncorrectable errors)

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=218795

--- Comment #4 from Mario Limonciello (AMD) (mario.limonciello@amd.com) ---
> pci 0000:35:00.0: 2.000 Gb/s available PCIe bandwidth, limited by 2.5 GT/s
> PCIe x1 link at 0000:00:04.1 (capable of 31.504 Gb/s with 8.0 GT/s PCIe x4
> link)

It's worth mentioning that this message is meaningless in the context of USB4. 
There were various discussions on the mailing lists about changing this, but it
never landed anywhere.

https://lore.kernel.org/linux-usb/20231103190758.82911-1-mario.limonciello@amd.com/

See specifically patch 8 for more context and the specs that indicate why it
behaves this way.

At least with AMD dGPUs put in eGPU enclosures this was causing problems for
amdgpu because if used pcie_bandwidth_available().  We've changed this in
amdgpu to look at the link partner to exclude this causing issues.

https://github.com/torvalds/linux/blob/v6.12-rc5/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c#L5903

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