I don't know if I was clear enough in my July 28 post, but it is physically impossible to make the A host port on a Tobi or Summit board work with OHCI because a piece of hardware is absent. I have tried to force the port into OHCI mode with only kernel panics as a result. To recap:
1. The USB OTG port is connected through the OTG interface of the TPS65950 chip and it does support both low/full speed and high speed, but cannot deliver more than 100mA.
2. The A host port is connected in an entirely different way: through a USB3326 chip which only includes hardware for full-speed. It has provisions to hand over full-speed to a separate full-speed PHY chip, but there is none on the Overo/Tobi/Summit.

For most people the most practical solution is to connect a hub to either of those ports. When using the OTG port the hub must be powered. When using the A port the hub must be high-speed.

I'm just repeating this such that if anyone in the future thinks they might be able to put the host port into full-speed mode they'll have a higher chance of finding this discussion and give up right away instead of wasting their time like I did.

Alexander

On Tue, Aug 2, 2011 at 6:49 PM, Victhor <victhor.foster@gmail.com> wrote:
Perhaps this could be done with a simple daemon that listens for a USB
enumeration error, which is what I get when I try to connect a full
speed device to the host port while in high speed mode. When this event
is detected, it will unload the EHCI module and load the OHCI one, which
would allow the usage of both high, full and low speed devices on their
appropriate modes. This is just a idea, I don't have any code for this
daemon.
> If it is of any interest, the splitter cable works and we can connect
> our full-speed device without a hub. If you can get hold of a
> solderable mini A or mini B plug, it is relatively easy to make such a
> cable from a regular A-to-miniB cable.
>
> Some important points however:
> 1. The plug that goes into the OTG port must have its ID pin grounded
> such that it is detected as a ‘mini A’ plug. We actually used a mini B
> plug but that doesn't matter as long as its ID pin is grounded. It was
> difficult enough to find solderable mini B plugs already, mini A plugs
> are extremely elusive.
> 2. The mini A plug must be plugged into the OTG port at boot! Nothing
> needs to be attached to it, but the plug itself must be connected to
> activate the OTG port. Once the Overo has booted with the plug
> connected, it can be disconnected and reconnected at leisure.
> 3. This splitter cable hack works in our case because the device does
> not perform power negotiation. If it would have told the USB port that
> it needs 400mA, the OTG port would say “no go” and shut down because
> it does not know that the device gets its power from elsewhere. There
> are hacks to disable this check but because the 100mA limit is a real
> hardware limit, it should not be tampered with unless you know what
> you're doing.
>
> It seems USB can be tamed on the Overo with the right strategy, yet it
> would have been much more convenient if a full-speed PHY had been
> included for the A host port and if proper hot-plugging had been
> supported…
>
> Alexander
>
> On Thu, Jul 28, 2011 at 5:54 PM, Alexander Thomas
> <alexander.thomas@esaturnus.com> wrote:
>         I found in the TPS65950 manual:
>         “The USB PHY supports the 3-pin DAT-SE0 and 4-pin VP-VM modes
>         of the CEA-2011 specification.”
>
>         But it doesn't matter anyway because at last I have figured
>         out that the USB A host port is connected to the OMAP through
>         a USB3326 PHY, therefore the above is irrelevant. The USB3326
>         only supports full-speed if accompanied by an external
>         full-speed PHY, which is absent on the Overo (unless I'm
>         really mistaken). I also got confirmation from someone at TI
>         that there is _no_ way to use a FS device on that port without
>         a hub. Major bummer.
>
>         Perhaps the least kludgy solution from an end-user perspective
>         would be a splitter cable with data lines from the OTG port
>         (which should support FS) and power to the A port, if that
>         will work at all…
>
>         Alexander
>
>
>
>
>         On Wed, Jul 27, 2011 at 4:16 PM, Steve Modica
>         <modica@small-tree.com> wrote:
>                 Do you have the omap3 manual?  I think that details
>                 the correct backend pin mode.  Steve S sent out a
>                 pointer to it on one of the threads.
>                 I'm definitely interested in this functionality as
>                 well.
>
>
>                 On Jul 27, 2011, at 5:13 AM, Alexander Thomas wrote:
>
>
>                 >
>                 > OK, I have figured out that I need to:
>                 > 1. disable EHCI and enable OHCI support in the
>                 > kernel,
>                 > 2. remove ehci init code from board-overo.c and add
>                 > missing ohci init code.
>                 >
>                 > I have to call usb_ohci_init with a
>                 > ‘ohci_hcd_omap_platform_data’ struct, but I have no
>                 > idea what value I should use for port_mode[1]. Given
>                 > that the ehci struct uses EHCI_HCD_OMAP_MODE_PHY, it
>                 > seems logical that I should use one of these four
>                 > possible ohci_omap3_port_mode values:
>                 >
>                 >     OMAP_OHCI_PORT_MODE_PHY_6PIN_DATSE0,
>                 >     OMAP_OHCI_PORT_MODE_PHY_6PIN_DPDM,
>                 >     OMAP_OHCI_PORT_MODE_PHY_3PIN_DATSE0,
>                 >     OMAP_OHCI_PORT_MODE_PHY_4PIN_DPDM
>                 >
>                 > Which one is correct for the Overo+Tobi?
>                 >
>                 > Alexander
>                 >
>                 > On Mon, Jul 25, 2011 at 6:29 PM, Victhor
>                 > <victhor.foster@gmail.com> wrote:
>                 >         There is a OHCI kernel module for the OMAP3
>                 >         USB controller, but I never
>                 >         had the opportunity to test it.
>                 >
>                 >         >
>                 >         > On Jul 25, 2011, at 10:02 AM, Alexander
>                 >         Thomas wrote:
>                 >         >
>                 >         > > On Mon, Jul 25, 2011 at 4:43 PM, Steve
>                 >         Modica
>                 >         > > <modica@small-tree.com> wrote:
>                 >         > >
>                 >         > >         On Jul 25, 2011, at 7:30 AM,
>                 >         Alexander Thomas wrote:
>                 >         > >
>                 >         > >         > Hi,
>                 >         > >         > Is there any expansion board
>                 >         for the Overo COMs that has
>                 >         > >         an Ethernet port and allows to
>                 >         directly attach a full-speed
>                 >         > >         USB device? We already have a
>                 >         Tobi but it proves to only
>                 >         > >         support high-speed devices.
>                 >         Unless I'm mistaken the only way
>                 >         > >         to connect a full-speed device
>                 >         like an USB audio device is
>                 >         > >         to connect it through a hub,
>                 >         which would complicate our
>                 >         > >         design considerably if we want
>                 >         to keep it a single unit.
>                 >         > >
>                 >         > >
>                 >         > >         You can put a full speed device
>                 >         on the OTG port.  It's an AB
>                 >         > >         port so there's nothing hard
>                 >         about that.  Get a miniAB to B
>                 >         > >         cable and you're all set.
>                 >         > >
>                 >         > > Except for the fact that the OTG port
>                 >         only delivers up to 100mA and
>                 >         > > the audio device requires 400mA.
>                 >         > >
>                 >         > > The strange thing is that the OMAP3530's
>                 >         specifications include
>                 >         > > “High-Speed/Full-Speed/Low-Speed
>                 >         Multiport USB Host Subsystem”. Why
>                 >         > > does the port on the Tobi only support
>                 >         high-speed? Can it be
>                 >         > > switched to low/full speed mode? We
>                 >         couldn't care less if that would
>                 >         > > mean losing high-speed.
>                 >         > >
>                 >         >
>                 >         >
>                 >         > The Host A port has the ability to support
>                 >         Full Speed devices *but*
>                 >         > you have to put the chip into OHCI mode
>                 >         and that requires a different
>                 >         > back end interface (which appears to be
>                 >         missing).  So if you want to
>                 >         > do this, you have to create that backend
>                 >         interface
>                 >         >
>                 >         > >
>                 >         > > Alexander
>                 >         > >
>                 >         > >
>                 >         ------------------------------------------------------------------------------
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>                 >         ------------------------------------------------------------------------------
>                 >         > Storage Efficiency Calculator
>                 >         > This modeling tool is based on
>                 >         patent-pending intellectual property that
>                 >         > has been used successfully in hundreds of
>                 >         IBM storage optimization engage-
>                 >         > ments, worldwide.  Store less, Store more
>                 >         with what you own, Move data to
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>                 >         ------------------------------------------------------------------------------
>                 >         Storage Efficiency Calculator
>                 >         This modeling tool is based on
>                 >         patent-pending intellectual property that
>                 >         has been used successfully in hundreds of
>                 >         IBM storage optimization engage-
>                 >         ments, worldwide.  Store less, Store more
>                 >         with what you own, Move data to
>                 >         the right place. Try It Now!
>                 >         http://www.accelacomm.com/jaw/sfnl/114/51427378/
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