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How to diagnose/restart malfunctioning USB-C after suspend?
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jroth
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Joined: 08 Aug 2017
Posts: 57

PostPosted: Thu Jan 10, 2019 11:27 pm    Post subject: How to diagnose/restart malfunctioning USB-C after suspend? Reply with quote

I have a laptop (A Dell XPS 13 model 9370) which has combination USB-C / Thunderbolt / Charging ports on the left hand side. Sometimes, after waking the computer up from a suspend, these ports don't work as USB-C ports anymore (but still work as charging ports), and I don't even see connect/disconnect messages from dmesg when I plug or unplug things.

I've enabled every USB-C / Thunderbolt kernel option cited on the wiki as needed for these ports, to no avail.

(The right-hand side port does not double as a thunderbolt or charging port and is unaffected by this problem)

What should I do to diagnose this problem and figure out how to fix it? And is there any command I can use to manually poke / wake up the USB ports after they've malfunctioned?
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geeksheik
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Joined: 07 Sep 2003
Posts: 98
Location: Zürich, Switzerland

PostPosted: Mon Jan 14, 2019 1:01 pm    Post subject: Reply with quote

I'm afraid I don't have direct knowledge of the USB-C interface under Linux (other than my phone connection which "just works").

However, as a first troubleshooting step, I'd recommend:

    Identify the relevant drivers involved

    Insure they're compiled as kernel modules

    Once the issue has occurred, unload the kernel module and reload it (rmmod X ; modprobe X)


If the driver is in a bad state, this might help to wake it up. Or if the hardware is in a bad state, reloading the driver(s) might cause a reset signal to be sent to the hardware.
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jroth
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Joined: 08 Aug 2017
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PostPosted: Mon Jan 28, 2019 11:33 pm    Post subject: Reply with quote

geeksheik wrote:
I'm afraid I don't have direct knowledge of the USB-C interface under Linux (other than my phone connection which "just works").

However, as a first troubleshooting step, I'd recommend:

    Identify the relevant drivers involved

    Insure they're compiled as kernel modules

    Once the issue has occurred, unload the kernel module and reload it (rmmod X ; modprobe X)


If the driver is in a bad state, this might help to wake it up. Or if the hardware is in a bad state, reloading the driver(s) might cause a reset signal to be sent to the hardware.


It looks like reloading the xhci_hcd and xhci_pci modules simultaneously is sometimes able to wake up the USB ports. But not always... I can't shake the feeling that there's a kernel option I missed somehow. Or is this something that a BIOS update could help with?
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