Re: [PATCH v4 4/6] usb: dwc2: hcd: fix possible successive vbus supply enables

[sashiko-bot@kernel.org]

> Relying on HPRT0_PWR value to call dwc2_vbus_supply_init() shows some
> corner case resulting in vbus enable count to increase.
> As consequence, dwc2_vbus_supply_exit call done when clearing
> PWR bit won't disable vbus (for example upon suspend request).
> 
> Address two case that has been seen:
> - In _dwc2_hcd_start(), external VBUS supply may have already been enabled,
>   before entering dwc2_hcd_reinit (e.g. the controller is in host mode,
>   without any device plugged).
> - Upon resume from low power in case registers have been lost. In clock
>   gating mode PM suspend flow doesn't disable vbus while in host mode:
>   - dwc2_port_suspend() enters clock gating (it sets lx_state to DWC2_L2)
>   - _dwc2_hcd_suspend() nothing more to do as already in L2.
>   - _dwc2_hcd_resume() - checks HPRT0_CONNSTS. If it's not set (register
>     loss) it sets HPRT0_PWR and call dwc2_vbus_supply_init().
> 
> Fix this by adding a boolean flag to balance vbus enable/disable calls
> instead of relying on HPRT0_PWR value. Clean the existing checks on pwr
> bit. A mutex is added as dwc2_vbus_supply_init/_exit calls can run
> concurrently from hub_control and dwc2_conn_id_status_change.
> 
> Fixes: cd7cd0e6cedf ("usb: dwc2: fix unbalanced use of external vbus-supply")
> 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=4