On Thursday 11 May 2006 8:49 am, Christopher Montgomery wrote:
> On 5/11/06, Christopher Montgomery <[EMAIL PROTECTED]> wrote:
> > On 5/10/06, David Brownell <[EMAIL PROTECTED]> wrote:
> > > On Wednesday 10 May 2006 10:35 am, Christopher Montgomery wrote:
> > > > In some
> > > > ways it's easier to just stack requests into the full-speed frame and
> > > > then plop the splits into whatever uFrame that happens to work out to,
> > > > even if that means that, eg, an interval 1 iso request might be
> > > > serviced in substantially different portions of the actual full-speed
> > > > frame.
> > >
> > > So with interval 1 (one packet per frame), two consecutive packets
> > > might go into uframes 7 then 0?  That'd be more like interval 1/8, and
> > > the next might be 15/8, and the next ... the notion was avoiding such
> > > relatively non-isochronous behaviors.
> [...]
> > Even if we restrict all the sitds of a given iso stream to
> > be scheduled in the same uframe, they're not guaranteed to actually
> > start in the same part of the uframe.. or even that uframe for that
> > matter, the TT is free to delay actually starting the transfer for up
> > to two additional uframes anyway.
> 
> I also forgot the example of OHCI, which appears to do some/all of the
> actual intraframe scheduling in hardware.  Is it just sending out
> transaction packets in the order they're queued? 

Yes, but ...

> (If so, the isos are occurring in totally random places in a given frame). 

Nope.  Periodic transfers take up the second 90% of the frame (at most).
And this doesn't have any scheduling conflicts with high speed transfers.


>       The EHCI FS/LS sceduling should probably be aping the OHCI
> behavior as it's known to work well.

No; ohci-hcd does some "best fit" logic, which happens to be cheap for
that hardware.  Whereas ehci-hcd uses "first fit", because it's costly
to do highspeed scheduling.

The similarity is basic:  see how much space is available, try the next
schedule point if this one doesn't have enough (in all schedule slots).
And that's already coded.



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