Re: USB4/TBT3 support

It would be nice to have Thunderbolt 4 support - and Thunderbolt 5 when 
it comes out - as well.

The speeds are quite high. I imagine many people would love to have 
40Gbps - 120Gbps / 80Gbps - 240Gbps on their laptop FreeBSD machine 
connected to their NAS.

Perhaps the FreeBSD Foundation could help find sponsorship for this work.

Cheers,
Yonas

On 2024-07-19 3:38 p.m., Joseph Mingrone wrote:
> Hello,
>
> Is anyone working on USB4 / Thunderbolt 3 (TBT3) support?
>
> Scott Long did a lot of work on this a few years ago, but he had to move
> on to other things, so he passed things on to Hans Petter Selasky.
> Fortunately, Hans Petter dropped the code in a public repository.
>
> https://github.com/hselasky/usb4
> https://github.com/hselasky/usb4/commit/dd85c216a2a6bee5361c7166595ba6ca461578b5
>
> Here is an overview of what Scott shared with me.
>
> Mostly completed work:
>
> - Debug/Trace framework
> - NHI controller driver
> - PCIe bridge driver
> - WMI driver
> - Integrated Connection Manager handshake and authentication handling
> - Router and Config Space layer handling (in progress, almost complete)
>
> Remaining work:
>
> - tbtconfig (userland tool)
> - man pages
> - DMAR/IOMMU integration, PCIe tunnelling control
> - Support for resetting and firmware flashing on the NHI via out-of-band control
> - Host Connection Manager
> - Cross-domain login
> - ThunderboltIP
>
> Here are the details that Scott shared.
>
>       The driver originally targeted the Thunderbolt 3 controllers that
>       were sold under the names “AlpineRidge" and “Icelake”, in the late
>       2010's, before the USB standards group publicly released the USB4
>       spec.  The driver set I wrote was complete enough to activate
>       Thunderbolt3 peripherals that otherwise would be disabled by
>       default when plugged in.  The driver also attempted to make it
>       easier to identify things like PCIe tunnels in the topology, but
>       that was mostly cosmetic.  Unfortunately, the AlpineRidge chips
>       proved to be extremely hard to work with despite their wide
>       availability, and I spent way too much time fighting them and not
>       enough time developing more useful functionality.  The WMI driver
>       was written to work around vexing problems with the Alpine Ridge
>       controller that I never figured out.
>
>       Much of the infrastructure from the TBT3 support extends to modern
>       USB4 controllers, but there are still a lot of missing pieces.  The
>       NHI driver doesn't know how to probe a USB4 controller yet, but
>       that should be easy to fix.  Even more important, though, is that
>       the code lacks a functional USB4 Connection Manager.  Most of the
>       pieces required to traverse the topology, discover routers and
>       adapters, read and write their properties, and build routes between
>       endpoints exists now, but there's no state machine yet that
>       integrates those pieces together into a real Connection Manager.
>       Without that, no attached peripherals will actually run.  The TBT3
>       controllers like AlpineRidge and IceLake have a connection manager
>       in firmware, so that's why those controllers function even with
>       minimal host OS support.  This isn't especially hard code to write,
>       but it's missing nonetheless.
>
>       Once the connection manager is written, it'll need to configure
>       connections with the USB3, PCIe, and DisplayPort devices that
>       operate over tunnels, and it'll need a cross domain handler for
>       connecting to another host.  USB3 tunnel support might require
>       significant changes in the USB3 stack in order to work with USB4.
>
>       Additionally you might need to write a USB-PD driver.  Without it,
>       negotiation on USB-C connectors for power delivery advertisements,
>       cable orientation, alt mode configuration, and USB3 vs USB4 lane
>       assignment might not work.  If those negotiations are not handled
>       then nothing that you plug into the port will even be seen by the
>       controller.
>
>       I'd totally stay away from spending time on supporting Falcon
>       Ridge, Alpine Ridge, and Titan Ridge controllers.  They're old,
>       they're extremely difficult to work with, and they're not worth the
>       headache.  In fact, just ignore all TBT3 controllers, and remove
>       the Internal Connection Manager code.  The ICM module isn't code
>       that I'm all that proud of anyways =-). Focus on writing an HCM,
>       supporting PCIe and DP tunneling, and integrating IOMMU protections
>       into both the NHI driver and the PCIe tunnel drivers.
>
>       One thing that would be pretty awesome is ThunderboltIP support.
>       It turns out that these controllers are really cheap 40Gbps
>       devices, and have the potential to perform pretty well at line rate
>       as a replacement for traditional 40Gb ethernet controllers, at
>       least in a point-to-point configuration.
>
> In short, a lot of work has been done, but a lot of work remains to be
> done.  The USB4 spec is complicated, and requires intimate knowledge
> of the USB-PD, USB-C, and USB3 specs.  There's also a spec for
> writing a Host Connection Manager that you’ll need to get familiar with.
>
> If anyone has already started or would like to continue Scott's work,
> could you please let me know?
>
> Joe