Re: [PATCH 5.10 211/290] xhci: Fix repeated xhci wake after suspend due to uncleared internal wake state

[Pavan Kondeti <quic_pkondeti@quicinc.com>]

+linux-usb

On Thu, Nov 18, 2021 at 03:21:54PM +0530, Rohith Kollalsi wrote:
> Hi Mathias,
> 
> This mail is regarding your upstream change in xhci file. There is a
> potential issue with your change which can cause noc error due to unclocked
> access.
> 
> Consider a case where a headset is connected to device and nothing is
> playing. As nothing is playing, usb bus wouldn't be active which leads to
> run time suspend ( i think this feature is not present upstream) as a part
> of which xhci_suspend will be called. Now all the clocks are also switched
> off. Now again when pm_suspend occurs due to disconnect, then again
> xhci_suspend occurs, but now registers can be accessed with clocks off
> leading to unclocked access. Can you please consider below change to prevent
> unclocked access.
> 
> 
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> 
> index 2728027..aaf212d 100644
> 
> --- a/drivers/usb/host/xhci.c
> 
> +++ b/drivers/usb/host/xhci.c
> 
> @@ -1013,13 +1013,13 @@ int xhci_suspend(struct xhci_hcd *xhci, bool
> do_wakeup)
> 
> xhci->shared_hcd->state != HC_STATE_SUSPENDED)
> 
>                 return -EINVAL;
> 
> +       if (!HCD_HW_ACCESSIBLE(hcd)) ---> this will prevent unclocked access
> when xhci_suspend occurs during second time during pm_suspend
> 
> + return 0;
> 
> +
> 
>         /* Clear root port wake on bits if wakeup not allowed. */
> 
>         xhci_disable_hub_port_wake(xhci, &xhci->usb3_rhub, do_wakeup);
> 
>         xhci_disable_hub_port_wake(xhci, &xhci->usb2_rhub, do_wakeup);
> 
> -       if (!HCD_HW_ACCESSIBLE(hcd))
> 
> -               return 0;
> 
> -
> 
>         xhci_dbc_suspend(xhci);
> 
> 
> Thanks,
> 
> Rohith