8df75f42f8
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> |
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| .. | ||
| atm | ||
| c67x00 | ||
| class | ||
| core | ||
| early | ||
| gadget | ||
| host | ||
| image | ||
| misc | ||
| mon | ||
| musb | ||
| otg | ||
| serial | ||
| storage | ||
| wusbcore | ||
| Kconfig | ||
| Makefile | ||
| README | ||
| usb-skeleton.c | ||
README
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("khubd").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.