On Thu, 11 Mar 2004, Malcolm Blaney wrote:

> Hi all,
> 
> I have been writing to the users list about usb not working on a Boser 
> single board computer, but have got around the problem by removing the 
> line: uhci->fsbr = 0;
> in uhci.c: alloc_uhci() in the 2.4.23 kernel.
> 
> Removing the line didn't work for 2.6 kernels, but changing it to:
> uhci->fsbr = 1;
> in uhci-hcd.c: uhci_start() in the 2.6.2 kernel did work. Setting it to 
> 1 also worked for the 2.4.x kernels instead of removing the line.
> 
> Without this change, the system hangs while detecting the new device.
> With the change though, the usb on the board is very slow, I've been 
> timing it at about 560Kb/s. I need ~6Mb/s -which you would expect from a 
> full speed device?

Setting uhci->fsbr to 1 has the effect of turning off full-speed bandwidth
reclamation, which will drastically reduce the USB throughput as you saw.
It shouldn't be necessary though.  I can't speak for the 2.4 kernel, but 
what happens with 2.6 when you leave the driver alone?  At what point 
during the detection procedure does the system hang?  What does the kernel 
log show up to that point?

Alan Stern



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