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From: Rob Herring <robh@kernel.org>
To: Dave Gerlach <d-gerlach@ti.com>
Cc: Ulf Hansson <ulf.hansson@linaro.org>,
	"Rafael J . Wysocki" <rjw@rjwysocki.net>,
	Kevin Hilman <khilman@kernel.org>,
	"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>,
	Tero Kristo <t-kristo@ti.com>,
	Sudeep Holla <sudeep.holla@arm.com>,
	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, 13 Jan 2017 13:25:47 -0600	[thread overview]
Message-ID: <CAL_JsqL+L1oHAOv7tLevzbtRFSKRs9J01SgF=HR_vNNqNV+4+Q@mail.gmail.com> (raw)
In-Reply-To: <3bb89649-fd2a-acc6-6968-e54a00842ce2@ti.com>

On Thu, Jan 12, 2017 at 9:27 AM, Dave Gerlach <d-gerlach@ti.com> wrote:
> Rob,
>
> On 01/11/2017 03:34 PM, Rob Herring wrote:
>>
>> On Mon, Jan 9, 2017 at 11:57 AM, Dave Gerlach <d-gerlach@ti.com> wrote:
>>>
>>> Rob,
>>>
>>> On 01/09/2017 11:50 AM, Rob Herring wrote:
>>>>
>>>>
>>>> On Wed, Jan 04, 2017 at 02:55:34PM -0600, Dave Gerlach wrote:
>>>>>
>>>>>
>>>>> Add a generic power domain implementation, TI SCI PM Domains, that
>>>>> will hook into the genpd framework and allow the TI SCI protocol to
>>>>> control device power states.
>>>>>
>>>>> Also, provide macros representing each device index as understood
>>>>> by TI SCI to be used in the device node power-domain references.
>>>>> These are identifiers for the K2G devices managed by the PMMC.
>>>>>
>>>>> Signed-off-by: Nishanth Menon <nm@ti.com>
>>>>> Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
>>>>> ---
>>>>> v2->v3:
>>>>>         Update k2g_pds node docs to show it should be a child of pmmc
>>>>> node.
>>>>>         In early versions a phandle was used to point to pmmc and docs
>>>>> still
>>>>>         incorrectly showed this.
>>>>>
>>>>>  .../devicetree/bindings/soc/ti/sci-pm-domain.txt   | 59 ++++++++++++++
>>>>>  MAINTAINERS                                        |  2 +
>>>>>  include/dt-bindings/genpd/k2g.h                    | 90
>>>>> ++++++++++++++++++++++
>>>>>  3 files changed, 151 insertions(+)
>>>>>  create mode 100644
>>>>> Documentation/devicetree/bindings/soc/ti/sci-pm-domain.txt
>>>>>  create mode 100644 include/dt-bindings/genpd/k2g.h
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/soc/ti/sci-pm-domain.txt
>>>>> b/Documentation/devicetree/bindings/soc/ti/sci-pm-domain.txt
>>>>> new file mode 100644
>>>>> index 000000000000..4c9064e512cb
>>>>> --- /dev/null
>>>>> +++ b/Documentation/devicetree/bindings/soc/ti/sci-pm-domain.txt
>>>>> @@ -0,0 +1,59 @@
>>>>> +Texas Instruments TI-SCI Generic Power Domain
>>>>> +---------------------------------------------
>>>>> +
>>>>> +Some TI SoCs contain a system controller (like the PMMC, etc...) that
>>>>> is
>>>>> +responsible for controlling the state of the IPs that are present.
>>>>> +Communication between the host processor running an OS and the system
>>>>> +controller happens through a protocol known as TI-SCI [1]. This pm
>>>>> domain
>>>>> +implementation plugs into the generic pm domain framework and makes
>>>>> use
>>>>> of
>>>>> +the TI SCI protocol power on and off each device when needed.
>>>>> +
>>>>> +[1] Documentation/devicetree/bindings/arm/keystone/ti,sci.txt
>>>>> +
>>>>> +PM Domain Node
>>>>> +==============
>>>>> +The PM domain node represents the global PM domain managed by the
>>>>> PMMC,
>>>>> +which in this case is the single implementation as documented by the
>>>>> generic
>>>>> +PM domain bindings in
>>>>> Documentation/devicetree/bindings/power/power_domain.txt.
>>>>> +Because this relies on the TI SCI protocol to communicate with the
>>>>> PMMC
>>>>> it
>>>>> +must be a child of the pmmc node.
>>>>> +
>>>>> +Required Properties:
>>>>> +--------------------
>>>>> +- compatible: should be "ti,sci-pm-domain"
>>>>> +- #power-domain-cells: Must be 0.
>>>>> +
>>>>> +Example (K2G):
>>>>> +-------------
>>>>> +       pmmc: pmmc {
>>>>> +               compatible = "ti,k2g-sci";
>>>>> +               ...
>>>>> +
>>>>> +               k2g_pds: k2g_pds {
>>>>> +                       compatible = "ti,sci-pm-domain";
>>>>> +                       #power-domain-cells = <0>;
>>>>> +               };
>>>>> +       };
>>>>> +
>>>>> +PM Domain Consumers
>>>>> +===================
>>>>> +Hardware blocks that require SCI control over their state must provide
>>>>> +a reference to the sci-pm-domain they are part of and a unique device
>>>>> +specific ID that identifies the device.
>>>>> +
>>>>> +Required Properties:
>>>>> +--------------------
>>>>> +- power-domains: phandle pointing to the corresponding PM domain node.
>>>>> +- ti,sci-id: index representing the device id to be passed oevr SCI to
>>>>> +            be used for device control.
>>>>
>>>>
>>>>
>>>> As I've already stated before, this goes in power-domain cells. When you
>>>> have a single thing (i.e. node) that controls multiple things, then you
>>>> you need to specify the ID for each of them in phandle args. This is how
>>>> irqs, gpio, clocks, *everything* in DT works.
>>>
>>>
>>>
>>> You think the reasoning for doing it this way provided by both Ulf and
>>> myself on v2 [1] is not valid then?
>>>
>>> From Ulf:
>>>
>>> To me, the TI SCI ID, is similar to a "conid" for any another "device
>>> resource" (like clock, pinctrl, regulator etc) which we can describe
>>> in DT and assign to a device node. The only difference here, is that
>>> we don't have common API to fetch the resource (like clk_get(),
>>> regulator_get()), but instead we fetches the device's resource from
>>> SoC specific code, via genpd's device ->attach() callback.
>>
>>
>> Sorry, but that sounds like a kernel problem to me and has nothing to
>> do with DT bindings.
>>
>>> From me:
>>>
>>> Yes, you've pretty much hit it on the head. It is not an index into a
>>> list
>>> of genpds but rather identifies the device *within* a single genpd. It is
>>> a
>>> property specific to each device that resides in a ti-sci-genpd, not a
>>> mapping describing which genpd the device belongs to. The generic power
>>> domain binding is concerned with mapping the device to a specific genpd,
>>> which is does fine for us, but we have a sub mapping for devices that
>>> exist
>>> inside a genpd which, we must describe as well, hence the ti,sci-id.
>>>
>>>
>>> So to summarize, the genpd framework does interpret the phandle arg as an
>>> index into multiple genpds, just as you've said other frameworks do, but
>>> this is not what I am trying to do, we have multiple devices within this
>>> *single* genpd, hence the need for the ti,sci-id property.
>>
>>
>> Fix the genpd framework rather than work around it in DT.
>
>
> I still disagree that this has nothing to do with DT bindings, as the
> current DT binding represents something different already. I am trying to
> extend it to give me additional information needed for our platforms. Are
> you saying that we should break what the current DT binding already
> represents to mean something else?

No idea because what's the current binding? From the patch, looks like
a new binding to me.

Rob

  reply	other threads:[~2017-01-13 19:26 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-04 20:55 [PATCH v3 0/4] ARM: K2G: Add support for TI-SCI Generic PM Domains Dave Gerlach
2017-01-04 20:55 ` [PATCH v3 1/4] PM / Domains: Add generic data pointer to genpd data struct Dave Gerlach
2017-01-04 20:55 ` [PATCH v3 2/4] dt-bindings: Add TI SCI PM Domains Dave Gerlach
2017-01-09 17:50   ` Rob Herring
2017-01-09 17:57     ` Dave Gerlach
2017-01-11 21:34       ` Rob Herring
2017-01-12 15:27         ` Dave Gerlach
2017-01-13 19:25           ` Rob Herring [this message]
2017-01-13 20:28             ` Dave Gerlach
2017-01-14  2:40               ` Rob Herring
2017-01-16 22:12                 ` Dave Gerlach
2017-01-17  7:48                   ` Tero Kristo
2017-01-17 23:37                     ` Rob Herring
2017-01-18  0:07                     ` Kevin Hilman
2017-01-18 23:03                       ` Rob Herring
2017-01-20 14:00                         ` Ulf Hansson
2017-01-20 14:18                           ` Sudeep Holla
2017-01-20 14:20                           ` Dave Gerlach
2017-01-20 16:52                             ` Ulf Hansson
2017-01-23 20:11                               ` Dave Gerlach
2017-01-24 10:03                                 ` Ulf Hansson
2017-01-25 16:59                                   ` Dave Gerlach
2017-01-25 21:13                                     ` Ulf Hansson
2017-01-25 22:32                                     ` Rob Herring
2017-01-26 15:09                                       ` Dave Gerlach
2017-01-26 16:00                                         ` Rob Herring
2017-01-04 20:55 ` [PATCH v3 3/4] soc: ti: Add ti_sci_pm_domains driver Dave Gerlach
2017-01-04 20:55 ` [PATCH v3 4/4] ARM: keystone: Drop PM domain support for k2g Dave Gerlach
2017-01-04 21:54 ` [PATCH v3 0/4] ARM: K2G: Add support for TI-SCI Generic PM Domains Santosh Shilimkar
2017-01-04 22:06   ` Dave Gerlach
2017-01-19 17:51     ` santosh.shilimkar
2017-01-19 18:59       ` Dave Gerlach
2017-01-19 19:04         ` Santosh Shilimkar

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