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Subject: Re: [PATCH] xhci: stop polling roothubs after shutdown
To:     Henry Lin <henryl@nvidia.com>,
        Mathias Nyman <mathias.nyman@intel.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20220401115916.104527-1-henryl@nvidia.com>
From:   Mathias Nyman <mathias.nyman@linux.intel.com>
Message-ID: <e4796a11-7571-b54e-cb82-87bb749709f1@linux.intel.com>
Date:   Tue, 5 Apr 2022 18:15:31 +0300
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On 1.4.2022 14.59, Henry Lin wrote:
> While rebooting, XHCI controller and its bus device will be shut down
> in order by .shutdown callback. Stopping roothubs polling in
> xhci_shutdown() can prevent XHCI driver from accessing port status
> after its bus device shutdown.
> 
> Take PCIe XHCI controller as example, if XHCI driver doesn't stop roothubs
> polling, XHCI driver may access PCIe BAR register for port status after
> parent PCIe root port driver is shutdown and cause PCIe bus error.
> 
> Signed-off-by: Henry Lin <henryl@nvidia.com>
> ---
>  drivers/usb/host/xhci.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
> index 2d378543bc3a..e7ae6766220e 100644
> --- a/drivers/usb/host/xhci.c
> +++ b/drivers/usb/host/xhci.c
> @@ -780,6 +780,14 @@ void xhci_shutdown(struct usb_hcd *hcd)
>  	if (xhci->quirks & XHCI_SPURIOUS_REBOOT)
>  		usb_disable_xhci_ports(to_pci_dev(hcd->self.sysdev));
>  
> +	/* Don't poll the roothubs after shutdown. */
> +	xhci_dbg(xhci, "%s: stopping usb%d port polling.\n",
> +			__func__, hcd->self.busnum);
> +	clear_bit(HCD_FLAG_POLL_RH, &hcd->flags);
> +	del_timer_sync(&hcd->rh_timer);
> +	clear_bit(HCD_FLAG_POLL_RH, &xhci->shared_hcd->flags);
> +	del_timer_sync(&xhci->shared_hcd->rh_timer);
> +
>  	spin_lock_irq(&xhci->lock);
>  	xhci_halt(xhci);
>  	/* Workaround for spurious wakeups at shutdown with HSW */
> 

Thanks, adding to queue

-Mathias