Re: usb: host: xhci: update event ring dequeue pointer on purpose

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Feb 20, 2020 at 07:52:09AM -0300, Fabio Estevam wrote:
> From: Peter Chen <peter.chen@nxp.com>
> 
> [ Upstream commit dc0ffbea5729a3abafa577ebfce87f18b79e294b ]
> 
> On some situations, the software handles TRB events slower
> than adding TRBs, then xhci_handle_event can't return zero
> long time, the xHC will consider the event ring is full,
> and trigger "Event Ring Full" error, but in fact, the software
> has already finished lots of events, just no chance to
> update ERDP (event ring dequeue pointer).
> 
> In this commit, we force update ERDP if half of TRBS_PER_SEGMENT
> events have handled to avoid "Event Ring Full" error.
> 
> Signed-off-by: Peter Chen <peter.chen@nxp.com>
> Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
> Link: https://lore.kernel.org/r/1573836603-10871-2-git-send-email-mathias.nyman@linux.intel.com
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Fabio Estevam <festevam@gmail.com>
> ---
> Hi,
> 
> One of our customer running 4.14 reported that this upstream patch
> fixes USB issues, so I am sending it to the stable trees.

It also needs to go to 4.19.y and 5.4.y, so I have added it there too.

thanks,

greg k-h