Re: [PATCH 1/5] dt/bindings: Add binding for the DA8xx MUSB driver

[Petr Kulhavy <petr-Qh/3xLP0EvwAvxtiuMwx3w@public.gmane.org>]

On 12.02.2016 17:21, Rob Herring wrote:
> On Thu, Feb 11, 2016 at 12:01:06PM +0100, Petr Kulhavy wrote:
>> + - mentor,power : Specifies the maximum current in milliamperes the controller can
>> +     supply in host mode.
> Still a no for me. Looks like this just sets hcd->power_budget. This
> property may not be a regulator, but ultimately the value depends on
> some regulator supplying Vbus. Also, given this has nothing to do with
> MUSB h/w, however this is described should be generic.

I understand your point that the description should be generic.
However the USB 2.0 specification does not define any relation between 
the bMaxPower provided by the device and the actual power control.
As far as I understand the value just serves the purpose to raise a flag 
to the user if the attached device would draw too much power, and not to 
enable it at all.
Further, the value used by the protocol is not necessarily related to 
the real current that can be supported. The maximum current supported by 
the protocol is 510mA.

For instance on my development board the real maximum current is limited 
only by the mains power-supply used.
So it cannot even be modelled in the DT as a regulator because the 
power-supply is not part of the HW and
everybody can take a different one.

So defining a regulator just to store this arbitrary USB 2.0 value is a 
bit overkill for me.

Regards
Petr
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