Re: [PATCH v6] usb: common: add API to set usb otg capabilities by device tree

[Li Jun <b47624-KZfg59tc24xl57MIdRCFDg@public.gmane.org>]

On Tue, Jun 23, 2015 at 10:43:28AM +0300, Roger Quadros wrote:
> > > 
> > > If the dr_mode was "otg" for such case and we want OTG disabled then it is really the DT fault.
> > 
> > It's ID pin detect for dual role switch as many current OTG controllers have.
> > not DT fault, its dt only has a dr_mode = "otg".
> > 
> > > We don't need to tackle this case. Just fix up the DT to dr_mode = "peripheral" if
> > > OTG behaviour is not needed.
> > > 
> > OTG behaviour is not needed, so we need disable HNP/SRP/ADP. but dr_mode =
> > "otg" as it already works fine with ID pin detect.
> 
> Do you know which platform has plain non-otg dual-role working as of today
> with dr_mode set to "otg"?

I don't know.
The dt property dr_mode is already there, and currently there are some platforms
as its user, so I assume those platforms either are non-otg dual-role, or real OTG
with HNP supported, I guess most are the former cases; chipidea is the later case.

> For TI platforms none of them have it working currently.
> 
So for Ti platforms, some enables non-otg dual-role function but do not use
dr_mode = "otg"?

For those only have non-otg dual-role platforms, no matter using dr_mode or not,
we need keep it's real OTG disabled for legacy users after it's controller
driver adds real OTG later.

> > 
> > > > 
> > > > How I make one decision in of_usb_updade_otg_caps()
> > > > for above 2 cases?(the otg-rev is 0 for both).
> > > > 
> > > 
> > > For case 3. otg-rev passed by controller is not 0. otg-rev is just not present in DT.
> > > 
> > 
> > Current OTG situation is not so simple, so that we can not use one simple
> > rule to handle legacy cases in a common place, but for a particular controller
> > driver, make decision on this is a simple work, I think.
> 
> OK. Let's continue with your apporach. Maybe USB maintainers can give their opinion
> as well.
> 
If some simple handling for all legacy platforms can be accepted, I am happy
to follow it in of_usb_update_otg_caps().

Felipe, Peter, any comments on this?

Li Jun

> Later if more controllers are trying to do the same thing then we can introduce a helper
> function for those controllers.
> 
Agree.

> cheers,
> -roger
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