Re: Genesys and IEEE 1394 (was: Re: Genesys Logic and Kernel 2.4)

[Alan Stern]

On Wed, 22 Sep 2004, Florian Weimer wrote:

> * Hisaaki Shibata:
> 
> >> +		/* According to the technical support people at Genesys Logic,
> >> +		 * devices using their chips have problems transferring more
> >> +		 * than 32 KB at a time.  In practice people have found that
> >> +		 * 64 KB works okay and that's what Windows does.  But we'll
> >> +		 * be conservative.
> >> +		 */
> >> +		if (ss->pusb_dev->descriptor.idVendor == USB_VENDOR_ID_GENESYS)
> >> +			ss->htmplt->max_sectors = 64;
> >
> > +			ss->htmplt.max_sectors = 64;
> >
> >> +
> 
> Christoph Biedl discovered that it's likely that a a similar
> workaround is needed in the IEEE 1394 code:
> 
> http://sourceforge.net/mailarchive/forum.php?thread_id=5128811&forum_id=5389

That change was not the important one.  The important part of the patch 
was this:

+               /* Genesys Logic interface chips need a 100us delay between
+                * the command phase and the data phase */
+               if (us->pusb_dev->descriptor.idVendor == USB_VENDOR_ID_GENESYS)
+                       udelay(100);

This is what affects the timing problem, by adding a 100-microsecond 
delay.

Alan Stern

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