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From:   Srinath Mannam <srinath.mannam@broadcom.com>
Date:   Tue, 3 Jul 2018 16:15:19 +0530
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Subject: Re: [PATCH v2 1/3] dt-bindings: thermal: Add binding document for SR thermal
To:     Rob Herring <robh@kernel.org>
Cc:     Zhang Rui <rui.zhang@intel.com>,
        Eduardo Valentin <edubezval@gmail.com>,
        Mark Rutland <mark.rutland@arm.com>,
        devicetree@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        BCM Kernel Feedback <bcm-kernel-feedback-list@broadcom.com>,
        Pramod Kumar <pramod.kumar@broadcom.com>
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Hi Rob,

Kindly provide your feedback.

Regards,
Srinath.

On Fri, Jun 22, 2018 at 11:21 AM, Srinath Mannam
<srinath.mannam@broadcom.com> wrote:
> Hi Rob,
>
> Please find my comments for the reason to have multiple DT nodes.
>
> On Thu, Jun 21, 2018 at 1:22 AM, Rob Herring <robh@kernel.org> wrote:
>> On Mon, Jun 18, 2018 at 02:01:17PM +0530, Srinath Mannam wrote:
>>> From: Pramod Kumar <pramod.kumar@broadcom.com>
>>>
>>> Add binding document for supported thermal implementation
>>> in Stingray.
>>>
>>> Signed-off-by: Pramod Kumar <pramod.kumar@broadcom.com>
>>> Reviewed-by: Ray Jui <ray.jui@broadcom.com>
>>> Reviewed-by: Scott Branden <scott.branden@broadcom.com>
>>> Reviewed-by: Srinath Mannam <srinath.mannam@broadcom.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.
>>> +
>>> +Example:
>>> +     tmons {
>>> +             compatible = "simple-bus";
>>> +             #address-cells = <1>;
>>> +             #size-cells = <1>;
>>> +             ranges;
>>> +
>>> +             tmon_ihost0: thermal@8f100000 {
>>> +                     compatible = "brcm,sr-thermal";
>>> +                     reg = <0x8f100000 0x4>;
>>> +             };
>>
>> You still haven't given me a compelling reason why you need a node per
>> register.
>>
>> You have a single range of registers. Make this 1 node.
>>
>
> We Have two reasons to have multiple nodes..
> 1. Our chip has multiple functional blocks. Each functional block has
> its own thermal zone.
> Functional blocks and their thermal zones enabled/disabled based on end product.
> Few functional blocks need to disabled for few products so thermal
> zones also need to disable.
> In that case, nodes of specific thermal zones are removed from DTS
> file of corresponding product.
>
> 2. Thermal framework provides sysfs interface to configure thermal
> zones and read temperature of thermal zone.
> To configure individual thermal zone, we need to have separate DT node.
> Same to read temperature of individual thermal zone.
> Ex: To read temperature of thermal zone 0.
>          cat /sys/class/thermal/thermal_zone0/temp
>      To configure trip temperature of thermal zone 0.
>           echo 110000 > /sys/class/thermal/thermal_zone0/trip_point_0_temp
>
> Also to avoid driver source change for the multiple products it is
> clean to have multiple DT nodes.
>
>> Rob