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

[sashiko-bot@kernel.org]

> dwc3_qcom_set_role_notifier() updates the VBUS override in QSCRATCH
> synchronously, from the context of the usb_role_switch_set_role()
> caller. The glue assumes that role switches only happen from a
> freezable workqueue, but that holds for the dwc3 core's mode switch,
> not for this notifier: the UCSI connector work, for one, runs on the
> non-freezable system workqueue.
> 
> On SM8750, when the USB cable is unplugged while the system is in
> s2idle, the UCSI connector work for the change runs before the devices
> have resumed. It switches the role to USB_ROLE_NONE, and the notifier
> accesses QSCRATCH while the glue clocks are still off, before
> dwc3_qcom_pm_resume() turns them back on. The access does not complete
> and the SoC resets. pm_runtime_resume_and_get() does not prevent this:
> runtime PM is disabled at that point and the device is still marked
> active, so it returns success without resuming anything.
> 
> While the glue is suspended for system sleep, only record the VBUS
> override update and apply it from dwc3_qcom_pm_resume() once the
> clocks are on. Apply it after the core has resumed, since resuming the
> gadget enables the override and the role switch is the more recent
> event. Serialize the notifier against the system suspend and resume
> callbacks with a mutex, so that a role switch can't run while the
> core or the glue is being suspended or resumed.
> 
> Fixes: 21188e8d6d75 ("usb: dwc3: qcom: Implement glue callbacks to facilitate runtime suspend")
> Cc: stable@vger.kernel.org
> Signed-off-by: Vladyslav Tymoshchuk <tvlad744@gmail.com>

Sashiko has reviewed this patch and found no issues.

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