[PATCH v2 3/4] usb: chipidea: ci13xxx-imx: add "dr_mode" property to device tree bindings

[Richard Zhao]

On Tue, Jul 03, 2012 at 09:02:40AM +0200, Lothar Waßmann wrote:
> Hi,
> 
> Richard Zhao writes:
> > On Tue, Jul 03, 2012 at 10:22:37AM +0800, Peter Chen wrote:
> > > > Hmm. I think it'd be reasonable to use dr_mode like the other bindings,
> > > > and have the default case be decided by the ID pin when dr_mode isn't
> > > > specified. Having different defaults for different bindings seems pretty
> > > > reasonable to me.
> > > 
> > > As far as I know, there is no USB Spec says the ID value should be
> > > used at device or host mode. At USB device and host driver, there
> > > should be NO ID related things, that is to say device or host driver
> > > should not care ID is grounded or floated, as ID may be grounded
> > > at device mode, and high at host mode for different board design.
> > > ID interrupt should only be enabled when dr_mode = otg;
> > I don't quite understand your point. All the discussions are based
> > on otg controllers.
> > > 
> > > Board design and customized usage (user may want to use only device mode
> > > for otg capable port) makes what USB role will be used
> > > at driver, so dr_mode at dts (or pdata->dr_mode at non-dt solution) can make
> > > the decision for driver how USB role will be used.
> > That's the case we need the property. But for fine otg hw design, we
> > don't need the property, right?
> > 
> > And to decide whether it's otg controller or not, the driver read the
> > capability registers.
> > 
> A user may wish to restrict even a 'fine otg hw design' to be used in
> pure host or device mode. That's where the dr_mode property jumps in.
Right, it _force_ the controller to a certain mode.

Thanks
Richard
> 
> 
> Lothar Waßmann
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