[PATCH v3] USB: mxs-phy: add basic otg support

[Chen Peter-B29397]

> 
> > The purpose for this patch is to have set_peripheral implementation,
> > but in current chipidea code, we don't need to know gadget at all,
> > as when id switch occurs, the core code know its role (device or host)
> > very well, and will call related stop/start function.
> >
> > We have already many code bind struct otg with struct phy, we'd better
> > split them at later code.
> >
> > A better approach to fix this problem is to either not call
> set_peripheral
> > if both device and host use chipidea driver, or implement otg struct
> > at chipidea driver.
> 
> Yes, I think the otg driver should be part of the chipidea driver, the
> only concern is the msm, although it can probably be converted once we
> have an otg driver. I'll have a look at it soon unless someone beats me
> to it.

Currently, we still have no auto-suspend and wakeup support, but msm supports
them, it may need much effort to move msm to current whole chipidea framework.
As it affects we go on implement id-switch function and other usb functions 
at chipidea, I hope we can have it soon, thanks. I also would like to help it
if you are busy on other things. 

> 
> The bigger plan was to implement a generic otg framework and base the
> chipidea's otg driver on that, instead of dragging in one more state
> machine and whatnot.
> 

Yes, we can transfer it to use generic otg framework once it is ready, but
first, it is better has own otg driver at chipidea.

> Regards,
> --
> Alex