Re: [PATCH v3 2/4] dt-bindings: Add TI SCI PM Domains

From: Sudeep Holla <sudeep.holla@arm.com>
To: Ulf Hansson <ulf.hansson@linaro.org>,
	Rob Herring <robh@kernel.org>,
	Kevin Hilman <khilman@baylibre.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>,
	Tero Kristo <t-kristo@ti.com>, Dave Gerlach <d-gerlach@ti.com>,
	"Rafael J . Wysocki" <rjw@rjwysocki.net>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	Nishanth Menon <nm@ti.com>, Keerthy <j-keerthy@ti.com>,
	Russell King <rmk+kernel@armlinux.org.uk>,
	Santosh Shilimkar <ssantosh@kernel.org>,
	Lokesh Vutla <lokeshvutla@ti.com>
Subject: Re: [PATCH v3 2/4] dt-bindings: Add TI SCI PM Domains
Date: Fri, 20 Jan 2017 14:18:40 +0000	[thread overview]
Message-ID: <c31cffa6-160a-de29-4ee7-fd74fc9cc743@arm.com> (raw)
In-Reply-To: <CAPDyKFqzs59N5bc89X-96Fgy9b=_+s8zYmHHshQeDrJCnaqprA@mail.gmail.com>

On 20/01/17 14:00, Ulf Hansson wrote:
> + Sudeep
> 
> On 19 January 2017 at 00:03, Rob Herring <robh@kernel.org> wrote:

>>
>> We could continue to use the power domain binding (maybe we already
>> are and that ship has sailed). I'm not totally against the idea even
>> if there is no power domain, but I'm not sold on it either. If we do
>> go this route, then I still say the id should be a cell in the
>> power-domain phandle.
>>
>> Another option is create something new either common or TI SCI
>> specific. It could be just a table of ids and phandles in the SCI
>> node. I'm much more comfortable with an isolated property in one node
>> than something scattered throughout the DT.
> 
> To me, this seems like the best possible solution.
> 
> However, perhaps we should also consider the SCPI Generic power domain
> (drivers/firmware/scpi_pm_domain.c), because I believe it's closely
> related.
> To change the power state of a device, this PM domain calls
> scpi_device_set|get_power_state() (drivers/firmware/arm_scpi.c), which
> also needs a device id as a parameter. Very similar to our case with
> the TI SCI domain.
> 
> Currently these SCPI device ids lacks corresponding DT bindings, so
> the scpi_pm_domain tries to work around it by assigning ids
> dynamically at genpd creation time.
> 

IIUC do you mean the binding for the power domain provider to have a
list of domain ids ? If so yes, we don't have one.

But the idea was to have the range to be continuous and create genpd for
the complete range. Though the SCPI specification lacked a command to
get the max. no. of domains supported. That's the reason we had to
introduce the num-domains(*) which may be optional if we have firmware
interface to obtain that information.

-- 
Regards,
Sudeep

(*) P.S: but it has been considered for SCMI(which is an improvement and
more flexible/extensible replacement/upgrade to SCPI) which will be
released soon.