Re: [coldsync-hackers] Sony T415 and FreeBSD..

[Greg KH <greg at kroah dot com>]

On Thu, Mar 21, 2002 at 03:35:05AM -0700, Cliff L. Biffle wrote:
> 
> As for the speed issues, does communication with the Palm over a relatively 
> small link (4-12mbps) really benefit from speed tweaking?  (This is an honest 
> question, I haven't tried.)

Yes it does.  

When I switched from only doing 1 data transfer per USB frame to packing
as many transfers as I could per frame (on Linux this is done by setting
the BULK_QUEUE flag on a urb), the transfer speed went up very
noticeably.  Sorry I don't remember the actual numbers.  It also helped
to send larger packets than the endpoint size (which effectively splits
up the transfer into smaller transfers at the USB host controller level,
removing the interrupt overhead.)

All of this is only done for sending data from the host to the device, I
haven't looked into any tweaks for receiving data.  This is ok, as
downloading "large" amounts of data to the device is much more common
than receiving data.

Also, it seems that the limiting factor on the Visor link is the Visor
itself.  It spends a lot of time in between "packets" that are sent to
it (the higher level Palm protocol packets, not USB packets.)  So there
is a limit of how fast the data will be transferred overall (the data is
sent very quickly, but there is delays between data packets, so the
throughput is decreased.)

However with faster processors showing up in Palm type devices, this
processing delay within the device should decrease, allowing more data
to be sent over the same time frame.

Did this help?

thanks,

greg k-h

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