linux-kernel - Re: [PATCH 1/3] dt-bindings: thermal: Add binding document for SR thermal

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Date:   Fri, 1 Jun 2018 09:29:02 -0500
From:   Rob Herring <robh@...nel.org>
To:     Srinath Mannam <srinath.mannam@...adcom.com>
Cc:     Zhang Rui <rui.zhang@...el.com>,
        Eduardo Valentin <edubezval@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        BCM Kernel Feedback <bcm-kernel-feedback-list@...adcom.com>,
        Pramod Kumar <pramod.kumar@...adcom.com>
Subject: Re: [PATCH 1/3] dt-bindings: thermal: Add binding document for SR thermal

On Fri, Jun 1, 2018 at 3:51 AM, Srinath Mannam
<srinath.mannam@...adcom.com> wrote:
> Hi Rob Herring,
>
> Thank you for the review.
> Please find my answers inline..
>
> On Thu, May 31, 2018 at 10:18 PM, Rob Herring <robh@...nel.org> wrote:
>> On Mon, May 28, 2018 at 11:11:22AM +0530, Srinath Mannam wrote:
>>> From: Pramod Kumar <pramod.kumar@...adcom.com>
>>>
>>> Add binding document for supported thermal implementation
>>> in Stingray.
>>>
>>> Signed-off-by: Pramod Kumar <pramod.kumar@...adcom.com>
>>> Reviewed-by: Ray Jui <ray.jui@...adcom.com>
>>> Reviewed-by: Scott Branden <scott.branden@...adcom.com>
>>> Reviewed-by: Srinath Mannam <srinath.mannam@...adcom.com>
>>> ---
>>>  .../bindings/thermal/brcm,sr-thermal.txt           | 45 ++++++++++++++++++++++
>>>  1 file changed, 45 insertions(+)
>>>  create mode 100644 Documentation/devicetree/bindings/thermal/brcm,sr-thermal.txt
>>>
>>> diff --git a/Documentation/devicetree/bindings/thermal/brcm,sr-thermal.txt b/Documentation/devicetree/bindings/thermal/brcm,sr-thermal.txt
>>> new file mode 100644
>>> index 0000000..33f9e11
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/thermal/brcm,sr-thermal.txt
>>> @@ -0,0 +1,45 @@
>>> +* Broadcom Stingray Thermal
>>> +
>>> +This binding describes thermal sensors that is part of Stingray SoCs.
>>> +
>>> +Required properties:
>>> +- compatible : Must be "brcm,sr-thermal"
>>> +- reg : memory where tmon data will be available.
>>
>> What type of memory is this?
> This is shared memory(cache-able) which is shared between two micro controllers.

What else is in this shared memory? You should probably be
representing that as a whole somewhere in DT.

> One micro controller update temperature of all thermal zones in this
> shared memory.
> thermal driver running on another micro controller monitors
> temperature data of all thermal zones.
>>
>>> +
>>> +Example:
>>> +     tmons {
>>> +             compatible = "simple-bus";
>>> +             #address-cells = <1>;
>>> +             #size-cells = <1>;
>>> +             ranges;
>>> +
>>> +             tmon_ihost0: thermal@...00000 {
>>> +                     compatible = "brcm,sr-thermal";
>>> +                     reg = <0x8f100000 0x4>;
>>> +             };
>>
>> Convince me that you need a node per register. This can all be
>> accomplished with a single node and either a single reg entry or a
>> series of reg entries.
>>
> In our system we have 6 different thermal zones. each node belongs to
> one thermal zone.
> thermal driver detects each node as separate thermal zone and monitors
> separately.
> register entry is only 4byte memory which contains the temperature
> value of respective thermal zone.
> Based on requirement we can increase or decrease the number thermal
> zones need to monitor.

Still, all this can be accomplished with a single node. Having a node
per register in DT doesn't scale.

Rob