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Revision 54f254f9


Added by aliguori over 12 years ago

uhci: rewrite UHCI emulator, fully async operation with multiple outstanding transactions (Max Krasnyansky)

This is esentially a re-write of the QEMU UHCI layer. My initial goal
was to support fully async operation with multiple outstanding async
transactions. Along the way I realized that I can greatly simplify
and cleanup the overall logic. There was a lot of duplicate and confusing
code in the UHCI data structure parsing and other places.
We were actually violating UHCI spec in handling async ISOC transaction
(host controller is not supposed to write into the frame pointer).

The reason I wanted to support fully async operation is because current
synchronous version is unusable with most devices exported from host
(via usb-linux.c). Transactions take a long time and the whole VM becomes
slow as hell.

Current async support is very rudimentory and for the most part
non-functional. Single transaction at a time is simply not enough. I have
a device for which XP driver submits both IN and OUT packets at the same
time. IN packet always times out unless OUT packet makes it to the device.
Hence we must be able to process both in order for that device to work.

The new code is backwards compatible and was first tested agains original
synchronous usb-linux.c and builtin usb devices like tablet which is also
synchronous. Rewrite of the usb-linux.c is coming up next.

Async support was tested against various XP versions (ie XP, SP2, SP3) and
a bunch of different USB devices: serial port controllers, mice, keyboard,
JTAG dongles (from Xilinx and Altera).

ISOC support was only lighly tested and needs more work. It's not any worse
than current code though.

UHCI parser changes are probably somewhat hard to review without the
understanding of the UHCI spec.
The async design should be fairly easy to follow. Basically we have a list
of async objects for each pending transfer. Async objects are tagged with
the original TD (transfer descriptor) address and token. We now support
unlimited number of outstanding isoc and one outstanding bulk/intr/ctrl
transfer per QH (queue head). UHCI spec does not have a clear protocol for
the cancelation of the trasfer requests. Driver can yank out TDs on any
frame boundary. In oder to handle that I added somewhat fancy TD validation
logic logic to avoid unnecessary cancelations.

Signed-off-by: Max Krasnyansky <>
Signed-off-by: Anthony Liguori <>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5050 c046a42c-6fe2-441c-8c8c-71466251a162


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