Very high data rate isochronous USB device ?

Hello,

I'm writing a USB device driver for a high-data rate device, for which I would 
like to use isochronous transfers (I already have working bulk transfers), 
but I can't get the expected (very high) data bandwidth.

The situation today is following :
- the device uses a High-speed USB 2.0 connection
- the device advertises one isochronous Endpoint, with up to 3 packets of 1024 
bytes per micro-frame, which corresponds to the designated target rate of 
around 200 Mbps (the endpoint descriptor has been checked and rechecked, and 
lsusb seems to acknowledge these parameters)
- the PC I use as host has three EHCI USB bridges : one is on the motherboard, 
and comes from Intel (it is a recent ICH6), and two additionnal PCI boards 
use chipsets from VIA and Ali
- I am using a quite recent linux kernel (2.6.18, coming with with OpenSuse 
10.2)
- I have copied the urb and iscochronous packet initialization and the 
completion routines from existing device drivers (one example I followed is 
drivers/media/dvb/b2c2/flexcop-usb.c)
- like in flexcop-usb.c, I have initialized the URBs with many packets 
(urb->number_of_packets is now a parameter of my device driver, and current 
values are 8 or 16)
- like in flexcop-usb.c, I have a big buffer cut in 8 or 16 chunks of 1kbyte, 
with offsets of 1 kbyte, one chunk for each packet of the URB
- like in flexcop-usb.c, the URBs are scheduled as fast as possible 
(urb->interval = 1;)
- I can read some data in isochronous mode, but with a lower data rate than 
the target : I only get one IN token for each micro-frame, instead of the 3 
expected
- I get the same behavior with all thre EHCI controllers (Intel, VIA and Ali)
- I have had a quick look at drivers/usb/host/ehci-sched.c, where the 
scheduling occurs, but I could not determine from iso_stream_init(), for 
example, which parameters I should set to have a higher data rate

Thus the question is : is there any driver in the linux source tree which can 
read more than one 1kbyte packet par micro-frame ? (or, which parameter set 
in flexcop_usb_transfer_init() should I change to attain a higher data 
rate ?)

	Many thanks in advance

	TfH

PS : I *have* had a look at the archives, but I could not find my answer ....
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