[FYI/RFC] usb: musb: DMA doesn't work with "nop" PHYs

[ABRAHAM, KISHON VIJAY]

Hi,

Couple of questions..

On Tue, Jul 3, 2012 at 4:08 AM, Mark A. Greer <mgreer at animalcreek.com> wrote:
> [The reason I'm sending this is that there is an issue but I probably
>  won't be able to spend much time on it for a while.  So, I'm sending
>  it in case a) it helps someone else who bumps into it and b) someone
>  else picks up and completes the fix.]
>
> Hello.
>
> In testing USB OTG Gadget on the am37x EVM with the mainline kernel
> I discovered that DMA doesn't work (but PIO does).  When I tested
> the same kernel on the BeagleBoard-xM (BBxM), which has essentially
> the same SoC, it worked fine.  They do have different OTG PHYs, though.
> The am37x EVM uses an ISP 1507 and the BBxM uses the PHY on the
> TPS65950 (twl4030).  The different PHYs means that they use different
> drivers in drivers/usb/otg.  The am37x EVM uses nop-usb-xceiv.c and
> the BBxM uses twl4030-usb.c.

Where does the comparator (VBUS) exist in am37x? Who will be first
interrupted when a cable is connected?

Thanks
Kishon