Re: [PATCH v4 5/6] usb: dwc2: hcd: don't disable external vbus in system suspend

[sashiko-bot@kernel.org]

> It's not required to remove port power upon system suspend, as explained
> in commit 113f86d0c302 ("usb: dwc2: Update partial power down entering by
> system suspend"). It can be addressed with hub ctrl (USB_PORT_FEAT_POWER).
> 
> When PM suspend flow disables Vbus while in host mode by
> calling dwc2_vbus_supply_exit()) in _dwc2_hcd_suspend() and the core has
> been put into clock gating mode, it triggers a disconnect and a resume
> IRQ (during suspend):
>   ++Disconnect Detected Interrupt++ (Host) a_host
>   ++Resume or Remote Wakeup Detected Interrupt++
> 
> That starts the wkp_timer in dwc2_host_exit_clock_gating() that will
> finally resume the port, e.g. call dwc2_wakeup_detected() and set
> lx_state = DWC2_L0 after ~70ms.
> 
> It races with PM suspend/resume flow. During _dwc2_hcd_resume() the port
> may already be in DWC2_L0 state skipping the dwc2_vbus_supply_init(),
> leaving the Vbus disabled.
> 
> So remove the disable of external Vbus in bus suspend to avoid this.
> 
> Fixes: 113f86d0c302 ("usb: dwc2: Update partial power down entering by system suspend")
> Cc: stable@vger.kernel.org
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261113-dwc2-low-power-fixes-stm32-v4-0-08a8c962a09e@foss.st.com?part=5