Re: [PATCH v3] usb: dwc3: Notify the glue of role changes from the mode switch work

[sashiko-bot@kernel.org]

> dwc3_usb_role_switch_set() and dwc3_drd_notifier() call the glue's
> pre_set_role() synchronously, from the context of whoever changes the
> role, while the mode switch itself runs from drd_work on a freezable
> workqueue. Not every caller is frozen during system sleep: 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
> dwc3_qcom_set_role_notifier() accesses QSCRATCH while the glue clocks
> are still off. 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.
> 
> Record the role and call pre_set_role() from __dwc3_set_mode() instead,
> so that the glue is not called while the system is suspended. The mode
> alone can't carry this: USB_ROLE_NONE maps to the default mode, so a
> switch between it and that role leaves the mode unchanged, and the glue
> still has to be told. Make the call before the checks that skip the
> mode switch, and only when a role was recorded, as the mode can also
> change without one from debugfs and from dwc3_setup_role_switch().
> 
> Role changes that come in while the work is frozen collapse into the
> last one, which is the state the hardware has to end up in.
> 
> Fixes: 21188e8d6d75 ("usb: dwc3: qcom: Implement glue callbacks to facilitate runtime suspend")
> Cc: stable@vger.kernel.org
> Suggested-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
> Signed-off-by: Vladyslav Tymoshchuk <tvlad744@gmail.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261111090122.134-1-tvlad744@gmail.com?part=1