Benjamin Herrenschmidt wrote:
>
> Ok, Back to USB hacking.
>
> I didn't reproduce my USB host disconnect problem after fixing a
> problem with the IO timings on the CPU bus to the controller.
>
> However, I noticed another issue. I tried plugging an USB mass storage
> device and experienced very very slow transfer speed (about 4k/sec).
>
> Using an analyser, I noticed that the driver is only tranfering one
> bulk (64 bytes) packet every 2 frames. Actually, I see that when
> "spying" a transfer:
>
> IN (ep 1) DATA0 (64 bytes)
> ACK
> SOF
> SOF
> IN (ep 1) DATA1 (64 bytes)
> SOF
> SOF
>
> etc...
>
> Before I start diving into your driver's guts, any clue about
> what's up ?
>
The one packet is a limitation of v0.8. But you can change it to
a larger number e.g. 4 or 8 (max 19) by replacing the 1s in
hc_add_trans()/hc_isp116x.c
- if (len > maxps *1)
- len = maxps * 1;
+ if (len > maxps * 8)
+ len = maxps * 8;
A larger number means more packets to the same Endpoint
per frame. But if the device
don't accept so many packets it NAKs and this means wasted
(expensive) data I/O to the isp1161.
More than 19 packets makes no sense because the USB can
only transfer up to 19 64-Bytes long packets within one frame.
And if the packets (endpoint maxpacketsize)
are shorter then 64 then the endpoint
most likely does not expect that much bandwidth, anyway.
But I have to think about a
good heuristic for the number of packets.
The wasted frames between the transfers seems to be a feature of the
isp1161.
> BTW. On the "device" side, now that those low-level IO stuffs are
> fixed, I could verify that my interface to the chip is working properly,
> I'll have a coupe of functions implemented soon, I'll post the code
> once done so we can think about a unified device interface.
>
OK.
- Roman
> Regards,
> Ben.
>
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