Re: [RFC 00/10] xhci: re-work command queue management

[Sarah Sharp]

Hi Keith,

You've told me in the past that you've run into an issue where you can
hang the xHCI driver when one of your TeleMetrum boards refuses to
respond to a Set Address command.

Can you test the following patchset, and see if it fixes your problem?
I've applied the patchset against 3.13 here:

https://git.kernel.org/cgit/linux/kernel/git/sarah/xhci.git/log/?h=for-usb-next-command-queue

Thanks,
Sarah Sharp

On Mon, Jan 13, 2014 at 05:05:49PM +0200, Mathias Nyman wrote:
> This is an attempt to re-work and solve the issues in xhci command
> queue management that Sarah has descibed earlier: 
> 
> Right now, the command management in the xHCI driver is rather ad-hock.  
> Different parts of the driver all submit commands, including interrupt 
> handling routines, functions called from the USB core (with or without the
> bus bandwidth mutex held).
> Some times they need to wait for the command to complete, and sometimes 
> they just issue the command and don't care about the result of the command.
> 
> The places that wait on a command all time the command for five seconds,
> and then attempt to cancel the command.  
> Unfortunately, that means if several commands are issued at once, and one of
> them times out, all the commands timeout, even though the host hasn't gotten
> a chance to service them yet.
> 
> This is apparent with some devices that take a long time to respond to the 
> Set Address command during device enumeration (when the device is plugged in).
> If a driver for a different device attempts to change alternate interface
> settings at the same time (causing a Configure Endpoint command to be issued),
> both commands timeout.
> 
> Instead of having each command timeout after five seconds, the driver should
> wait indefinitely in an uninterruptible sleep on the command completion.  
> A global command queue manager should time whatever command is currently
> running, and cancel that command after five seconds.
> 
> If the commands were in a list, like TDs currently are, it may be easier to keep
> track of where the command ring dequeue pointer is, and avoid racing with events.
> We may need to have parts of the driver that issue commands without waiting on
> them still put the commands in the command list.
> 
> The Implementation:
> -------------------
> 
> First step is to create a list of the commands submitted to the command queue.
> To accomplish this each command is required to be submitted with a properly
> filled command structure containing completion, status variable and a pointer to
> the command TRB that will be used.
> 
> The first 7 patches are all about creating these command structures and
> submitting them when we queue commands.
> The command structures are allocated on the fly, the commands that are submitted
> in interrupt context are allocated with GFP_ATOMIC.
> 
> Next, the global command queue is introduced. Commands are added to the queue
> when trb's are queued, and remove when the commad completes. 
> Also switch to use the status variable and completion in the command struct.
> 
> A new timer handles command timeout, the timer is kicked every time when a 
> command finishes and there's a new command waiting in the queue, or when a new
> command is submitted to an _empty_ command queue.
> Timer is deleted when the the last command on the queue finishes (empty queue)
> 
> The old cancel_cmd_list is removed. 
> When the timer expires we simply tag the current command as "ABORTED" and start
> the ring abortion process. Functions waiting for an aborted command to finish are
> called after the command abortion is completed.
> 
> Mathias Nyman (10):
>   xhci: Use command structures when calling xhci_configure_endpoint
>   xhci: use a command structure internally in xhci_address_device()
>   xhci: use command structures for xhci_queue_slot_control()
>   xhci: use command structures for xhci_queue_stop_endpoint()
>   xhci: use command structure for xhci_queue_new_dequeue_state()
>   xhci: use command structures for xhci_queue_reset_ep()
>   xhci: Use command structured when queuing commands
>   xhci: Add a global command queue
>   xhci: Use completion and status in global command queue
>   xhci: rework command timeout and cancellation,
> 
>  drivers/usb/host/xhci-hub.c  |  42 ++--
>  drivers/usb/host/xhci-mem.c  |  22 +-
>  drivers/usb/host/xhci-ring.c | 532 ++++++++++++++-----------------------------
>  drivers/usb/host/xhci.c      | 264 +++++++++++----------
>  drivers/usb/host/xhci.h      |  43 ++--
>  5 files changed, 373 insertions(+), 530 deletions(-)
> 
> -- 
> 1.8.1.2
> 
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