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

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Message-ID: <57D1A821.3010904@ti.com>
Date:   Thu, 8 Sep 2016 13:04:17 -0500
From:   Dave Gerlach <d-gerlach@...com>
To:     Kevin Hilman <khilman@...libre.com>,
        Ulf Hansson <ulf.hansson@...aro.org>
CC:     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@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-pm@...r.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

Hi,
On 09/08/2016 12:38 PM, Kevin Hilman wrote:
> 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
>

I am first trying to leverage the dev_attach/detach and start/stop 
callbacks that Ulf suggested without creating a single genpd per device 
and it looks like it will work for us. I appreciate the alternative 
suggestions but I agree we'd like to leverage as much of the existing 
genpd framework as we can and avoid going down the omap_device style 
implementation path.

Regards,
Dave