On Wed, May 05, 2004 at 08:34:41AM -0700, David Brownell wrote:
> Hasjim Williams wrote:
>
> >The Viper Embedded Linux Developer Kit is based around an XScale
> >device, so it needs to use an Embedded USB Host Controller. The
> >Philips ISP1161A1 is such an example. An Embedded USB Host controller
> >is not the same thing as a standard desktop OHCI controller. They have
> >similar registers but different interfaces to the CPU's Bus. But the
> >long story cut short is, that you can't run any ohci driver for an
> >embedded host controller.
>
> That's not true in general; look for example at the OMAP OHCI.
> The Linux work it needs to work better in embedded space is more
> along the lines of power savings and new features (OTG) than basic
> functionality ... it's OHCI, driver found in current 2.6 kernels.
> (Other vendors use OHCI too, including Intel in their latest PXA.)
>
> The ISP1161 isn't really OHCI, and that's why it needs its own
> driver. There might be discrete chips that implement OHCI too,
> but ones like ISP1161 and SL811HS don't. Which is fine ... but
> it means that their drivers aren't going to be as robust, since
> they can't leverage the verification done daily on OHCI by all
> the millions of Penguins (and Quokkas).
Hmm, as we're currently thinking about replacing the dreaded SL811
for our next PXA263 design with an ISP 116x, that's bad news for me ;)
I thought, skimming the specs from Philips, that the ISP 116x is OHCI,
but does'nt have memory-mapped registers (it's PIO).
Now, If one would add some layer to the OHCI code which does the register
access, i.e. for memory-mapped do readx()/writex(), and for the PIO types
do PIO, then one could add a "simple" bus glue for ISP 116x chips and the like.
If that's not a Really Good Idea (TM), then I wonder which options one
has, e.g. what USB Host chips are out there which do OHCI _and_ can talk to
a processor w/o PCI?
Thanks,
Stefan E.
>
> - Dave
>
>
>
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