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

[Jon Hunter <jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>]

On 18/02/16 16:00, Ulf Hansson wrote:
> [...]
> 
>>>
>>> What about the pm_clk_* API which was built for tracking clocks
>>> associated with devices for runtime PM.
>>>
>>> IOW, you could pm_clk_add(pg->pmc->dev, pg->clks[i]) and then your
>>> _enable_clocks() would become pm_clk_suspend() an dyour
>>> _disable_clocks() would become pm_clk_resume().
>>
>> Very interesting, I was not aware of this.
>>
>>> I might not be following the mapping between PMC and PGs though so not
>>> sure pg->pmc->dev is the right struct device, but you get the idea.
>>
>> Yes, so this will not work here as-is, because the pmc->dev is common to
>> all pm-domains (it is the device that creates all the pm-domains). So to
>> make this work, I would need to create a device for each pm-domain and
>> add the clocks to that.
>>
>> I see that this works very well for normal drivers, but it does not feel
>> so natural for pm-domains where we don't have a device struct today. By
>> the way, the rockchip pm-domains implementation is very much in the same
>> boat as tegra, where there are multiple clocks per pm-domain and it is
>> handled by a simple list. So I am not sure if you think that we should
>> be turning all pm-domains registered by pm_genpd_init() into a device
>> and then we can make use of these pm_clk_XXXX() APIs?
>>
>> I have implemented the generic clk APIs that Ulf and I discussed for
>> handling multiple clocks, but if we think that this is a better way,
>> then I will hold off for now.
> 
> I think Kevin has a point that we already have PM clocks to build upon.
> Could we perhaps try to extend that API instead to suite this needs as well?

We certainly could and I am not against it, however, it means that we
need to create a device structure for each pm-domain. If you and Kevin
are ok with me adding this to pm_genpd_init(), then I can give it a try.

> I do realize that it will make this patchset more complicated. As I
> stated earlier, this was just an idea I had, so to be clear I won't
> hold back an ack for this patchset, if you decide to deal with this in
> separate "improvement" step.

Thanks
Jon