linux-kernel - Re: [PATCH 3/3] soc: ti: Add ti_sci_pm

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Date:   Thu, 08 Sep 2016 10:38:27 -0700
From:   Kevin Hilman <khilman@...libre.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Dave Gerlach <d-gerlach@...com>, Nishanth Menon <nm@...com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Keerthy <j-keerthy@...com>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Tero Kristo <t-kristo@...com>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Sudeep Holla <sudeep.holla@....com>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree\@vger.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel\@lists.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-pm\@vger.kernel.org" <linux-pm@...r.kernel.org>,
        Jon Hunter <jonathanh@...dia.com>
Subject: Re: [PATCH 3/3] soc: ti: Add ti_sci_pm_domains driver

Ulf Hansson <ulf.hansson@...aro.org> writes:

> [...]
>
>>
>> One more idea...
>>
>> Since you don't really have a domain (a group of devices), what you
>> really have is each device having an independent power switch, so as Ulf
>> suggested, what you really need is for all the devices to share the same
>> set of runtime PM callbacks that call SCI.  The only difference is the
>> unique ID.
>>
>> Rather than using all of genpd, you could also just use a pm_domain
>> which is what genpd is built on top of (and also omap_device, which
>> you're probably familiar with also.)
>
> Even if this would work as well, the downside would be that you need
> to re-invent the parts related to the DT parsing, the probing/removal
> and attaching/detaching of the device to the PM domain.
>
> You probably don't want to go there... :-)

All you'd need to read from DT would be the device-specific ID for
TI-SCI, and that could be done at bind time with a notifier.  The, in
that same notifier, if a TI-SCI ID exists, it would get added to the
pm_domain.

Anyways, your original proposal is much preferred if it can work.  I'm
just throwing out another option because I really don't like one genpd
per device.

Kevin