Re: diagnosing resume failures after disconnected USB4 drives (Was: Re: PCI/ASPM: Fix L1SS saving (linus/master commit 7507eb3e7bfac))

[Mika Westerberg <mika.westerberg@linux.intel.com>]

Hi,

On Mon, Feb 10, 2025 at 10:17:47PM -0800, Kenneth Crudup wrote:
> 
> The setup is fairly simple (once I'd figured out the failure mode):
> 
> - Have an ASMedia 246x NVMe-to-USB4 housing (with NVMe drive) attached to
> the system via my TB4 dock (CalDigit TS4, but I've had it happen with a Dell
> dock as well (either with the drive mounted, or not) when I suspend
> 
> - Resume with the drive disconnected (i.e., I've gone from home to the
> office).

I see this is fairly normal use-case (sans the disk I guess). Steps to
follow are then something like:

1. Boot the system, nothing connected.
2. Connect CalDigit TS4 (PCIe tunnel is enabled by the UI) to the host Type-C port.
3. Connect ASMedia NVMe to CalDigit downstream Type-C port (PCIe tunnel is enabled by the UI).
4. Verify that the NVMe is visible (lspci, lsblk).

The topology looks like below:

  Host <- TB -> CalDigit TS4 <- TB -> NVMe

5. Suspend the system (close the lid).
6. Unplug the CalDigit TS4.
7. Resume the system (open the lid).

Expectation: system wakes up just fine.
Actual behavior: system crashes and burns.

Do you BTW, unmount the filesystem before you suspend?

> It doesn't happen every time, and for some crazy reason elapsed time between
> suspend and resume seems to make it more likely to happen. Plus it seems
> directly attaching the drive (i.e., no dock in between) doesn't cause
> resumes to fail.

It would be good to see the dmesg output (with thunderbolt.dyndbg=+p) with
these connected, even without suspending so see if there is anything
missing. Since it is Dell system I would expect they have tested this in
Linux pretty well so probably we don't see anything weird there.

I have similar here (not the same devices though) so I can try on my end if
this repros.