[PATCH V5 11/14] soc: tegra: pmc: Add generic PM domain support

[Ulf Hansson]

On 11 February 2016 at 10:13, Jon Hunter <jonathanh at nvidia.com> wrote:
>
> On 10/02/16 18:25, Ulf Hansson wrote:
>
> [snip]
>
>>>> Perhaps there's a way to allow the generic PM domain to control this
>>>> by itself. If we for example used the struct device corresponding to
>>>> the powergate driver, genpd could use it to distinguish between
>>>> various instances of genpd structs..!? Maybe it would simplify the way
>>>> to deal with removing domains?
>>>
>>> Yes, that would be ideal. However, would have require changing
>>> genpd_init()? I am not sure how genpd would be able to access the device
>>> struct for the powergate driver because we don't provide this via any
>>> API I am aware of? And I am guessing that you don't wish to expose the
>>> gpd_list to the world either.
>>>
>>> If there is an easy way, I am open to it, but looking at it today, I am
>>> not sure I see a simple way in which we could add a new API to do this.
>>> However, may be I am missing something!
>>
>> If we add a new __pm_genpd_init() API, that could require a struct
>> device to be provided. That API will thus invoke the existing
>> pm_genpd_init() but also deal with the extra things needed here.
>>
>> I would also allow such an API to return an error code.
>>
>> Correspondingly, pm_genpd_remove() could be required to be provided
>> with a struct device.
>>
>> Existing users of pm_genpd_init() can then convert to
>> __pm_genpd_init() whenever suitable.
>>
>> Of course, another option is just to add new member in the genpd
>> struct for the struct *device. The caller of pm_genpd_init() could
>> check it, but allow it to be NULL. Although, the pm_genpd_remove() API
>> would require that pointer to the struct device to be set...
>>
>> What do you think?
>
> Yes, sounds good. May be it is simpler just to add a new member and let
> the platform genpd driver handle it.
>
> I am wondering if in addition to pm_genpd_remove(), we then just have a
> function called pm_genpd_remove_tail(), which allows you to pass the
> struct device pointer and will remove the last pm-domain from the
> gpd_list and return the genpd pointer if successful. Internally, it will
> call pm_genpd_remove(). It seems to me that if there are nested
> pm-domains, then we probably want to remove them starting from the tail
> as opposed to the head.
>
> How does that sound?

Why not make pm_genpd_remove() to behave as you describe for
pm_genpd_remove_tail()?
That's probably the only sane way to remove genpds anyhow!?

Kind regards
Uffe