On Thu, Jun 23, 2011 at 01:14:04PM -0400, Alan Stern wrote: > On Thu, 23 Jun 2011, Kirill Smelkov wrote: > > > > At 480 Mb/s, each microframe holds 7500 bytes (less if you count > > > bit-stuffing). 4% of that is 300 bytes, which is not enough for a > > > 512-byte bulk packet. I think you'd run into trouble trying to do any > > > serious bulk transfers on such a tight schedule. > > > > Yes, you seem to be right. > > > > I still think 4% is maybe enough for control traffic. > > It should be.
Ok then. At least devices could be start/stopped, and frankly if someone loads the bus with two high-bandwidth isoc streams, there is no reason to expect any bulk transfer to happen at all. > > > > @@ -571,6 +579,14 @@ static int ehci_init(struct usb_hcd *hcd) > > > > hcc_params = ehci_readl(ehci, &ehci->caps->hcc_params); > > > > > > > > /* > > > > + * tell user, if using non-standard (80% == 100 usec/uframe) > > > > bandwidth > > > > + */ > > > > + if (uframe_periodic_max != 100) > > > > + ehci_info(ehci, "using non-standard max periodic > > > > bandwith " > > > > + "(%u%% == %u usec/uframe)", > > > > + 100*uframe_periodic_max/125, > > > > uframe_periodic_max); > > > > + > > > > + /* > > > > > > Check for invalid values. This should never be less than 100 or > > > greater than 125. > > > > Ok. By the way, why should we limit it to be not less than 100? > > Likewise, a user who knows exactly what he/she is doing could limit > > periodic bandwidth to be less than 80% required by USB specification. > > What's the point? If you want to use less than 80% of your bandwidth > for periodic transfers, go ahead and do so. You don't need to change > the limit. I though it would be good for generality -- i.e. if someone wants to limit maximum isoc bandwidth to say 50% so that would never be overallocated by that limit that would be handy. But I agree - it's a bit artificial, so in updated patch I've left what you originally suggested to be 100 <= uframe_periodic_max < 125 (ommitting =125). Thanks, Kirill -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
