Re: [Qemu-devel] [RFC] multi phase reset

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

Hi Damien,

On 3/1/19 5:52 PM, Peter Maydell wrote:
> On Fri, 1 Mar 2019 at 15:34, Damien Hedde <damien.hedde@greensocs.com> wrote:
>> On 3/1/19 12:43 PM, Peter Maydell wrote:
>>> In my design the only thing that I thought would happen in phase 3
>>> was the "clear the resetting flag", but you've moved that to RELEASE.
>>> What's left ? Do you have a concrete example where we'd need this?
>>
>> I hesitated to remove this phase (would be easy to add it after if it is
>> really needed). I see 2 cases where it might be useful.

If I RELEASE a PLL which need some time to warm up and stabilize, once
stabilized it moves the device to the POST phase where it is ready?

>>
>> To stay in my use case for clocks, here how it can be used: For an uart,
>> during release phase, the clock will propagate and only after every
>> release phases has been executed we will have the final/valid input
>> frequency.
>> So we can either recompute the uart baudrate every time the clock change
>> due to propagation or wait till post phase to do it once for all (and
>> initialize the backend parameters). But it is probably no big deal for
>> this case if we don't have post phase.
> 
> I think I'd rather have the model be simpler rather than
> complicate it for the sake of optimisation. It's not like
> we reset very frequently...