Re: [PATCH v2] usb: dwc3: qcom: Defer VBUS override update during system suspend

[Thinh Nguyen]

On Tue, Nov 10, 2026, Vladyslav Tymoshchuk wrote:
> On Thu, Nov 05, 2026 at 12:02:46AM +0000, Thinh Nguyen wrote:
> > Hi Vladyslav,
> >
> > Could you test this change instead to see if it resolves the issue?
> 
> It does. OnePlus Pad 3 (SM8750, UCSI over pmic_glink), v7.3-rc5 plus
> board patches, with my dwc3-qcom v2 reverted and nothing else holding
> back pmic_glink notifications during suspend. I added debug prints to
> dwc3_usb_role_switch_set(), to __dwc3_set_mode() before the glue call,
> and to dwc3_qcom_set_role_notifier(), with the device's PM state.
> 
> The same kernel without your change resets the SoC when the cable is
> unplugged in s2idle. The last lines in the ramoops console:
> 
>   PM: suspend-to-idle
>   role_switch_set ->0 (pm suspended 1 late 1 noirq 1)
>   qcom notifier: role 2->0, vbus override 0 (pm suspended 1 noirq 1)
> 
> With your change there was no reset. Each suspend run was 150 s of
> s2idle ended by an RTC alarm, with the cable changed by hand during it:
> 
>   unplug                  2 runs
>   plug in                 1 run
>   unplug, plug back in    1 run
>   cable left plugged in   1 run
> 
> plus unplug and plug in while awake. In the suspend runs every role
> switch call came with dwc3 in the noirq phase and only stored the role.
> The glue was called once, with the last role, when the freezable
> workqueue was thawed:
> 
>   PM: suspend-to-idle
>   role_switch_set ->0 (pm suspended 1 late 1 noirq 1)
>   PM: resume of devices complete after 108.388 msecs
>   Restarting tasks: Starting
>   drd_work passes role 0 to the glue
>   qcom notifier: role 2->0, vbus override 0 (pm suspended 0 noirq 0)
>   Restarting tasks: Done
> 
> Unplug and plug in during one suspend came down to a single DEVICE
> call, which dwc3-qcom skips since its role did not change. After every
> resume with the cable in, the NCM gadget was configured again within
> 5 s. While awake, the glue still gets NONE and DEVICE although the dr
> mode stays peripheral, so the call has to stay ahead of the early
> returns in __dwc3_set_mode(), where you put it.
> 
> Host mode, with a USB stick on the port instead of the cable: plugging
> and unplugging the stick while awake works as before, and so did two
> suspends with the stick left in. With the stick unplugged in s2idle
> (3 runs) the NONE call again came in noirq and was only stored, and
> drd_work passed it on after thaw:
> 
>   PM: suspend-to-idle
>   role_switch_set ->0 (pm suspended 1 late 1 noirq 1)
>   PM: resume of devices complete after 2554.135 msecs
>   Restarting tasks: Starting
>   drd_work passes role 0 to the glue
>   qcom notifier: role 1->0, vbus override 1 (pm suspended 0 noirq 0)
>   xhci-hcd xhci-hcd.3.auto: remove, state 1
>   Restarting tasks: Done
> 
> The host-mode suspends were on a kernel that also keeps the USB GDSCs
> of gcc-sm8750 in retention. Without that the xHCI came back from
> s2idle with an SMMU fault and "HC died" in all three runs I tried,
> with the stick unplugged or left in. The dwc3 code was the same in
> both kernels, so that is a separate problem. I have no result for
> plugging the stick in during s2idle: the port did not detect the stick
> every time, also while awake, and I have not found out why yet.
> 
> Two comments go stale with this change: dwc3_qcom_set_role_notifier()
> says role changes are protected by the usb_role_switch mutex, while now
> they are serialized by dwc->mutex in drd_work, and the @pre_set_role
> kerneldoc could say that it is called from drd_work, so not during
> system sleep.

Please update the comments.

> 
> Will you post it, or would you like me to send it as v3 in place of my
> dwc3-qcom patch?
> 
> Tested-by: Vladyslav Tymoshchuk <tvlad744@xxxxxxxxx> # SM8750

Thanks for the details and testing. Can you send it as v3 with my
Suggested-by tag?

Suggested-by: Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx>

Thanks,
Thinh