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

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

Hello Rob,

is there any follow-up on this one?

Thanks
Petr

On 12.02.2016 18:24, Petr Kulhavy wrote:
>
> 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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