Add support for allocating streams for USB 3.0 bulk endpoints. See
Documentation/usb/bulk-streams.txt for more information about how and why
you would use streams.
When an endpoint has streams enabled, instead of having one ring where all
transfers are enqueued to the hardware, it has several rings. The ring
dequeue pointer in the endpoint context is changed to point to a "Stream
Context Array". This is basically an array of pointers to transfer rings,
one for each stream ID that the driver wants to use.
The Stream Context Array size must be a power of two, and host controllers
can place a limit on the size of the array (4 to 2^16 entries). These
two facts make calculating the size of the Stream Context Array and the
number of entries actually used by the driver a bit tricky.
Besides the Stream Context Array and rings for all the stream IDs, we need
one more data structure. The xHCI hardware will not tell us which stream
ID a transfer event was for, but it will give us the slot ID, endpoint
index, and physical address for the TRB that caused the event. For every
endpoint on a device, add a radix tree to map physical TRB addresses to
virtual segments within a stream ring.
Keep track of whether an endpoint is transitioning to using streams, and
don't enqueue any URBs while that's taking place. Refuse to transition an
endpoint to streams if there are already URBs enqueued for that endpoint.
We need to make sure that freeing streams does not fail, since a driver's
disconnect() function may attempt to do this, and it cannot fail.
Pre-allocate the command structure used to issue the Configure Endpoint
command, and reserve space on the command ring for each stream endpoint.
This may be a bit overkill, but it is permissible for the driver to
allocate all streams in one call and free them in multiple calls. (It is
not advised, however, since it is a waste of resources and time.)
Even with the memory and ring room pre-allocated, freeing streams can
still fail because the xHC rejects the configure endpoint command. It is
valid (by the xHCI 0.96 spec) to return a "Bandwidth Error" or a "Resource
Error" for a configure endpoint command. We should never see a Bandwidth
Error, since bulk endpoints do not effect the reserved bandwidth. The
host controller can still return a Resource Error, but it's improbable
since the xHC would be going from a more resource-intensive configuration
(streams) to a less resource-intensive configuration (no streams).
If the xHC returns a Resource Error, the endpoint will be stuck with
streams and will be unusable for drivers. It's an unavoidable consequence
of broken host controller hardware.
Includes bug fixes from the original patch, contributed by
John Youn <John.Youn@synopsys.com> and Andy Green <AGreen@PLXTech.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
8df75f42f8