Re: [RFC PATCH 1/5] Device Power: introduce power controller

[Roger Quadros <rogerq@ti.com>]

On 12/03/2012 05:00 AM, Ming Lei wrote:
> On Mon, Dec 3, 2012 at 12:02 AM, Andy Green <andy.green@linaro.org> wrote:
>> On 02/12/12 23:01, the mail apparently from Ming Lei included:
>>
>>> Power controller is an abstract on simple power on/off switch.
>>>
>>> One power controller can bind to more than one device, which
>>> provides power logically, for example, we can think one usb port
>>> in hub provides power to the usb device attached to the port, even
>>> though the power is supplied actually by other ways, eg. the usb
>>> hub is a self-power device. From hardware view, more than one
>>> device can share one power domain, and power controller can power
>>> on if one of these devices need to provide power, and power off if
>>> all these devices don't need to provide power.
>>
>>
>> What stops us using struct regulator here?  If you have child regulators
>> supplied by a parent supply, isn't that the right semantic already without
>> introducing a whole new thing?  Apologies if I missed the point.
> 
> There are two purposes:
> 
> One is to hide the implementation details of the power controller because
> the user doesn't care how it is implemented, maybe clock, regulator, gpio
> and other platform dependent stuffs involved, so the patch simplify the usage
> from the view of users.
> 

Which user are you talking about?

AFAIK for Panda we only need a regulator and a clock for each root port.
IMHO we should just use the existing regulator and clock frameworks.

> Another is that several users may share one power controller, and the
> introduced power controller can help users to use it.
> 

True. e.g. the same regulator could be used to power 3 root hub ports in
a ganged setup. But the regulator framework is sufficient to deal with
that. Each port will call regulator_get() and regulator_enable() and the
physical regulator won't be disabled till all of them have called
regulator_disable().

regards,
-roger