Question on OTG transceivers

Question on OTG transceivers

[Bill Gatliff]

Guys:


I have a Beagleboard-like unit here that uses two SMSC USB3320C-EZK
PHYs: one for EHCI (usb1), the other for OTG (usb0).

Two questions.  First, the code in drivers/usb/otg/ulpi.c looks like it
might be what I need (my attempts so far with the "nop" transceiver have
ended in failure).  Am I right?

Second, it looks like otg_set_transceiver() assumes there is only one
transceiver in the system.  On a device like the OMAP3530 with multiple
ports, this seems like an odd assumption--- and one that clearly isn't
accurate for my platform.  Or am I paying attention to the wrong stuff?

Can anyone help navigate me through the trees in this forest?  :)


Thanks!


b.g.

-- 
Bill Gatliff
Embedded systems training and consulting
http://billgatliff.com
bgat@billgatliff.com

RE: Question on OTG transceivers

[Gadiyar, Anand]

 

> -----Original Message-----
> From: linux-omap-owner@vger.kernel.org 
> [mailto:linux-omap-owner@vger.kernel.org] On Behalf Of Bill Gatliff
> Sent: Thursday, March 18, 2010 3:05 AM
> To: linux-omap@vger.kernel.org
> Subject: Question on OTG transceivers
> 
> Guys:
> 
> 
> I have a Beagleboard-like unit here that uses two SMSC USB3320C-EZK
> PHYs: one for EHCI (usb1), the other for OTG (usb0).
> 
> Two questions.  First, the code in drivers/usb/otg/ulpi.c looks like it
> might be what I need (my attempts so far with the "nop" transceiver have
> ended in failure).  Am I right?
> 

Actually, the way the ehci-omap driver is currently written, it assumes
the transceiver is present and available - you don't need a separate
driver to access it.

For that matter, the same probably holds for the OTG driver as well - you
really don't need a driver for transparent transceivers like the SMSC332x.

I'm not sure why the code was written this way to introduce NOP XCEIVs
(need to go through the changelog to find out why, maybe).

> Second, it looks like otg_set_transceiver() assumes there is only one
> transceiver in the system.  On a device like the OMAP3530 with multiple
> ports, this seems like an odd assumption--- and one that clearly isn't
> accurate for my platform.  Or am I paying attention to the wrong stuff?
> 
> Can anyone help navigate me through the trees in this forest?  :)

I think this assumption comes from some part of the OTG spec which says
that OTG devices can have only one external USB port.

But embedded devices can certainly have more than one transceiver (for example
to connect an on-board USB device without exposing an external port) - so
maybe there's no point keeping this restriction any more.


- Anand

Re: Question on OTG transceivers

[Bill Gatliff]

Gadiyar, Anand wrote:
>  
> Actually, the way the ehci-omap driver is currently written, it assumes
> the transceiver is present and available - you don't need a separate
> driver to access it.
>
> For that matter, the same probably holds for the OTG driver as well - you
> really don't need a driver for transparent transceivers like the SMSC332x.
>   

But I get an OOPS and the system halts when I don't have a transceiver
driver...



b.g.

Re: Question on OTG transceivers

[Felipe Balbi]

On Mon, Mar 22, 2010 at 11:06:32AM -0500, Bill Gatliff wrote:
> Gadiyar, Anand wrote:
> >  
> > Actually, the way the ehci-omap driver is currently written, it assumes
> > the transceiver is present and available - you don't need a separate
> > driver to access it.
> >
> > For that matter, the same probably holds for the OTG driver as well - you
> > really don't need a driver for transparent transceivers like the SMSC332x.
> >   
> 
> But I get an OOPS and the system halts when I don't have a transceiver
> driver...

that smells like you're using the otg port.

-- 
balbi

RE: Question on OTG transceivers

[Gadiyar, Anand]

Bill Gatliff wrote:
> Gadiyar, Anand wrote:
> > Actually, the way the ehci-omap driver is currently written, it assumes
> > the transceiver is present and available - you don't need a separate
> > driver to access it.
> >
> > For that matter, the same probably holds for the OTG driver as well - you
> > really don't need a driver for transparent transceivers like the SMSC332x.
> >   
> 
> But I get an OOPS and the system halts when I don't have a transceiver
> driver...
> 

Care to post a bootlog and your .config file? Maybe it's just a simple CONFIG option that
you are missing?