Re: [Qemu-devel] [PATCH][RFC 0/14] implement power chip

[Peter Maydell <peter.maydell@linaro.org>]

On 19 March 2013 09:31, li guang <lig.fnst@cn.fujitsu.com> wrote:
> 在 2013-03-19二的 09:05 +0000，Peter Maydell写道：
>> I suspect this should involve more modelling of actual
>> control signals between the power controller and
>> the devices, not methods on the base class.
>>
>
> do we have to realize something like signals which are actually
> only some copper wires?
> I think we just emulate the real work, that is when some signals
> asserted, we just call corresponding method to do something
> by these embedded method, I want to let devices take care
> of power event(on/off/suspend/wakeup) themselves.

The point is that how exactly power controllers connect
to devices, and which devices respond to reset/suspend/etc
is a property of the individual machine being modelled.
An x86 PC will be different from an ARM devboard which is
different again from the Exynos4 ARM SoC. So to allow this
flexibility, you have to let the machine model do the configuration,
which you do by having the model wire up the power controller
to the devices in the same way it's done on hardware.

>> > I'm eager to get more comments and discussion.
>> > This idea simply based on system board design convention,
>> > I'm not saying a power chip has signals directly connected
>> > to all devices, I mean system board and its devices should
>> > have protocol to deal with power state changes.
>>
>> Hardware does it with signals, so should we.
>
> can these signals be viewed as the calling of corresponding methods?

In some ways, they are -- but the wiring up of the source of
the call to the implementation is done at runtime as devices
are connected together.

-- PMM