Re: [PATCH v3] usb: hub: lack of clearing xHC resources

[Alan Stern <stern@rowland.harvard.edu>]

On Fri, Feb 28, 2025 at 07:50:25AM +0000, Pawel Laszczak wrote:
> The xHC resources allocated for USB devices are not released in correct
> order after resuming in case when while suspend device was reconnected.
> 
> This issue has been detected during the fallowing scenario:
> - connect hub HS to root port
> - connect LS/FS device to hub port
> - wait for enumeration to finish
> - force host to suspend
> - reconnect hub attached to root port
> - wake host
> 
> For this scenario during enumeration of USB LS/FS device the Cadence xHC
> reports completion error code for xHC commands because the xHC resources
> used for devices has not been properly released.
> XHCI specification doesn't mention that device can be reset in any order
> so, we should not treat this issue as Cadence xHC controller bug.
> Similar as during disconnecting in this case the device resources should
> be cleared starting form the last usb device in tree toward the root hub.
> To fix this issue usbcore driver should call hcd->driver->reset_device
> for all USB devices connected to hub which was reconnected while
> suspending.
> 
> Fixes: 3d82904559f4 ("usb: cdnsp: cdns3 Add main part of Cadence USBSSP DRD Driver")
> cc: <stable@vger.kernel.org>
> Signed-off-by: Pawel Laszczak <pawell@cadence.com>
> 
> ---
> Changelog:
> v3:
> - Changed patch title
> - Corrected typo
> - Moved hub_hc_release_resources above mutex_lock(hcd->address0_mutex)
> 
> v2:
> - Replaced disconnection procedure with releasing only the xHC resources

Reviewed-by: Alan Stern <stern@rowland.harvard.edu>