linux-kernel - Re: [PATCH V10 1/4] dt-bindings: fsl: scu: add thermal binding

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Message-ID: <CAL_JsqJct4BztHEak+=iNK3G7dwYR-pQPeUqb4kBnEdRQMLr6A@mail.gmail.com>
Date:   Thu, 28 Feb 2019 08:49:10 -0600
From:   Rob Herring <robh@...nel.org>
To:     Anson Huang <anson.huang@....com>
Cc:     "mark.rutland@....com" <mark.rutland@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "will.deacon@....com" <will.deacon@....com>,
        "rui.zhang@...el.com" <rui.zhang@...el.com>,
        "edubezval@...il.com" <edubezval@...il.com>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
        Aisheng Dong <aisheng.dong@....com>,
        "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
        "sboyd@...nel.org" <sboyd@...nel.org>,
        Daniel Baluta <daniel.baluta@....com>,
        Andy Gross <andy.gross@...aro.org>,
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Subject: Re: [PATCH V10 1/4] dt-bindings: fsl: scu: add thermal binding

On Wed, Feb 27, 2019 at 6:48 PM Anson Huang <anson.huang@....com> wrote:
>
> Hi, Rob
>
> Best Regards!
> Anson Huang
>
> > -----Original Message-----
> > From: Rob Herring [mailto:robh@...nel.org]
> > Sent: 2019年2月28日 7:55
> > To: Anson Huang <anson.huang@....com>
> > Cc: mark.rutland@....com; shawnguo@...nel.org;
> > s.hauer@...gutronix.de; kernel@...gutronix.de; festevam@...il.com;
> > catalin.marinas@....com; will.deacon@....com; rui.zhang@...el.com;
> > edubezval@...il.com; daniel.lezcano@...aro.org; Aisheng Dong
> > <aisheng.dong@....com>; ulf.hansson@...aro.org; sboyd@...nel.org;
> > Daniel Baluta <daniel.baluta@....com>; Andy Gross
> > <andy.gross@...aro.org>; horms+renesas@...ge.net.au; heiko@...ech.de;
> > arnd@...db.de; maxime.ripard@...tlin.com; bjorn.andersson@...aro.org;
> > jagan@...rulasolutions.com; enric.balletbo@...labora.com;
> > marc.w.gonzalez@...e.fr; olof@...om.net; devicetree@...r.kernel.org;
> > linux-kernel@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-
> > pm@...r.kernel.org; dl-linux-imx <linux-imx@....com>
> > Subject: Re: [PATCH V10 1/4] dt-bindings: fsl: scu: add thermal binding
> >
> > On Wed, Feb 27, 2019 at 08:46:21AM +0000, Anson Huang wrote:
> > > NXP i.MX8QXP is an ARMv8 SoC with a Cortex-M4 core inside as system
> > > controller, the system controller is in charge of system power, clock
> > > and thermal sensors etc. management, Linux kernel has to communicate
> > > with system controller via MU (message unit) IPC to get temperature
> > > from thermal sensors, this patch adds binding doc for i.MX system
> > > controller thermal driver.
> > >
> > > Signed-off-by: Anson Huang <Anson.Huang@....com>
> > > ---
> > > Changes since V9:
> > >     - change #thermal-sensor-cells value in example to 1, since there are
> > other
> > >       thermal sensors inside system controller, it is just because there are
> > still
> > >       some issue, so system controller does NOT expose them for now,
> > they could
> > >       be exposed later, so it should be 1 from HW perspective.
> > > ---
> > >  .../devicetree/bindings/arm/freescale/fsl,scu.txt   | 21
> > +++++++++++++++++++++
> > >  1 file changed, 21 insertions(+)
> > >
> > > diff --git
> > > a/Documentation/devicetree/bindings/arm/freescale/fsl,scu.txt
> > > b/Documentation/devicetree/bindings/arm/freescale/fsl,scu.txt
> > > index 72d481c..855270b 100644
> > > --- a/Documentation/devicetree/bindings/arm/freescale/fsl,scu.txt
> > > +++ b/Documentation/devicetree/bindings/arm/freescale/fsl,scu.txt
> > > @@ -122,6 +122,21 @@ RTC bindings based on SCU Message Protocol
> > > Required properties:
> > >  - compatible: should be "fsl,imx8qxp-sc-rtc";
> > >
> > > +Thermal bindings based on SCU Message Protocol
> > > +------------------------------------------------------------
> > > +
> > > +Required properties:
> > > +- compatible:                      Should be :
> > > +                             "fsl,imx8qxp-sc-thermal"
> > > +                           followed by "fsl,imx-sc-thermal";
> > > +
> > > +- #thermal-sensor-cells:   See
> > Documentation/devicetree/bindings/thermal/thermal.txt
> > > +                           for a description.
> > > +
> > > +- imx,sensor-resource-id:  A single integer for single thermal zone's
> > resource ID or
> > > +                           an array of integers to specify each thermal
> > zone's sensor
> > > +                           resource ID.
> >
> > Can't you put the resource ids in the thermal-sensor cells? Why do you need
> > to list them here?
>
> For the thermal-sensor cells, if you meant the argument of tsens phandle, then
> the reason is that argument is for sensor index starting from 0, previous I use
> it for our resource ID, but it looks confused, since user will think there are many
> sensors there per Eduardo's comment.
>
> +                       thermal-sensors = <&tsens 0>;
>
> If you meant putting it in each thermal sensor node instead of "tsens" node, then
> in previous patch series, I put this " imx,sensor-resource-id " property in each thermal
> sensor node, but the thermal sensor nodes are parsed by common thermal framework,
> thermal driver will need to find the thermal zone node and go through every child node
> to get the resource id again, so Eduardo suggested to put it in our platform tsens node, that makes
> our thermal driver code much more simple.

The phandle args are meant to be an id typically. There's absolutely
no requirement they are 0-N based. They often are because things like
interrupts are 0-N or clocks have no h/w id. If you already have an
id, use it. Don't invent your own.

Rob