[speedtouch] Re: isochronous support broken?

[Alistair John Strachan]

On Monday 23 January 2006 12:36, Duncan Sands wrote:
> Hi Alistair,
>
> > usb 4-1.4: reset full speed USB device using ehci_hcd and address 4
>
> a bug fix for ehci + iso urbs bandwidth allocation just got posted to the
> usb mailing list.  So I suggest trying uhci instead (OK, I just saw that
> you tried it).
>
> ...
>
> > As you can see, the recv buffer has dropped but nothing has changed. Then
> > I had the idea to remove ehci-hcd, and force it to use uhci-hcd for the
> > USB 1.1 device (I have no USB 2.x devices anyway). This was successful:
>
> ...
>
> > I was able to bring pppd up over the interface. /proc/bus/usb/devices
> > looks like this; only 79% utilisation.
>
> What do you mean by "79% utilisation"?
>
> > T:  Bus=01 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=12  MxCh= 2
> > B:  Alloc=710/900 us (79%), #Int=  2, #Iso=  4

                          ^^
This, which I assume is bus utilisation.

> > D:  Ver= 1.10 Cls=09(hub  ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
> > P:  Vendor=0000 ProdID=0000 Rev= 2.06
> > S:  Manufacturer=Linux 2.6.15.1 uhci_hcd
> > S:  Product=UHCI Host Controller
> > S:  SerialNumber=0000:00:10.0
> > C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=  0mA
> > I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
> > E:  Ad=81(I) Atr=03(Int.) MxPS=   2 Ivl=255m
> >
> > My bandwidth is still locked to just under 500KB/s (4MBits). So either a)
> > isoc isn't working or b) you need to do more than just switch from bulk
> > to isoc to get 8Mbits from this device.
>
> This is what I see.  Using bulk I max out at a bit under 4 megabaud.  With
> isoc I max out at an even slower rate!
>
> > The Windows workaround does not suggest this, but I suppose it is
> > impossible to tell.
>
> What is "the windows workaround"?  (I don't have windows, which makes
> comparing with windows a bit awkward for me).

To go from Bulk to Isochronous. See here:

http://bbs.adslguide.org.uk/showthreaded.php?Cat=&Board=bulldog&Number=1939137&page=0&view=expanded&sb=5&o=0&fpart=

And here:

http://www.speedtouch.co.uk/330highspeed.asp

>
> > If it's a useful datapoint, I used to get sporadic errors and the USB LED
> > would flash RED if the bandwidth was held close to 4Mbit for a long
> > period of time. This no longer seems to happen with isoc, suggesting the
> > bandwidth bottleneck has been lifted. However, I do not see the 6.6
> > megabits I've synced at.
>
> Are you talking about linux or windows here?  Can you get 6.6 mb with
> windows?

I've not seen it myself, but supposedly it is possible (given the comments on 
many forums, such as adslguide.org.uk).

> Anyway, I think it likely that there is something wrong with the driver. 
> But it could be a hardware limitation.  Testing with windows should clear
> that up.  If you can do some experiments with windows, that would be great.

I'd like to help in any way I can, but putting Windows on the machine routing 
our internet is out of the question. It also probably wouldn't work, given 
the speed of that machine.

-- 
Cheers,
Alistair.

'No sense being pessimistic, it probably wouldn't work anyway.'
Third year Computer Science undergraduate.
1F2 55 South Clerk Street, Edinburgh, UK.