Re: [PATCH] thunderbolt: Resume PCIe bridges after switch is found on AMD USB4 controller

[Kai-Heng Feng]

On Mon, Sep 5, 2022 at 11:34 PM Mika Westerberg
<mika.westerberg@xxxxxxxxxxxxxxx> wrote:
>
> On Mon, Sep 05, 2022 at 11:21:36PM +0800, Kai-Heng Feng wrote:
> > > Hmm, so you see the actual hotplug but the tunneled PCIe link may not be
> > > detected? Does the PCIe "Card Present" (or Data Link Layer Active)
> > > status change at all or is it always 0?
> >
> > It changes only after tb_switch_add() is called.
>
> I doubt tb_switch_add() does anything but instead it is the established
> PCIe tunnel that then shows up as it toggles the Card Present bit or so.
> But that should also trigger PME if the root port is in D3 so you should
> see this wake if everything works accordingly (unless I'm missing
> something).

You are right. Sometimes it may still fail to detect hotplugged device
right after tb_switch_add().
At which point PCIe tunnels are established? Is it after tb_scan_port()?

I found that it's cleaner to wakeup hotplug ports via iterating device
link consumers at the end of tb_scan_port().

According to your commit b2be2b05cf3b1c7b499d3b05decdcc524879fea7
("thunderbolt: Create device links from ACPI description"), it states
"The _DSD can be added to tunneled USB3 and PCIe ports, and is needed to
make sure the USB4 NHI is resumed before any of the tunneled ports so
the protocol tunnels get established properly before the actual port
itself is resumed. Othwerwise the USB/PCI core find the link may not be
established and starts tearing down the device stack."

So isn't waking them up a logical thing to do here?

>
> So if you do this:
>
> 1. Boot the system up, nothing connected
> 2. Plug in the TBT/USB4 device but do not authorize the PCIe tunnel
> 3. Wait for the TBT/USB4 domain to enter sleep (runtime suspend)
> 4. Authorize the PCIe tunnel
>
>   # echo 1 > .../authorized
>
> The established PCIe tunnel should trigger PME and the root port then
> should be able to detect the PCIe link. Can you add full dmesg with
> "thunderbolt.dyndbg=+p" in the command line to the bug?

dmesg attached. Unfortunately there's no PME.

Kai-Heng