linux-kernel - Re: [PATCH v1 1/6] dt-bindings: soc: mediatek: Add DVFSRC bindings for MT8183 and MT8195

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Date: Wed, 17 Apr 2024 10:26:06 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Conor Dooley <conor@...nel.org>
Cc: djakov@...nel.org, robh@...nel.org, krzysztof.kozlowski+dt@...aro.org,
 conor+dt@...nel.org, matthias.bgg@...il.com, lgirdwood@...il.com,
 broonie@...nel.org, keescook@...omium.org, gustavoars@...nel.org,
 henryc.chen@...iatek.com, linux-pm@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org,
 kernel@...labora.com, wenst@...omium.org, amergnat@...libre.com
Subject: Re: [PATCH v1 1/6] dt-bindings: soc: mediatek: Add DVFSRC bindings
 for MT8183 and MT8195

Il 16/04/24 19:30, Conor Dooley ha scritto:
> On Tue, Apr 16, 2024 at 06:28:58PM +0100, Conor Dooley wrote:
>> On Tue, Apr 16, 2024 at 05:38:00PM +0200, AngeloGioacchino Del Regno wrote:
>>> Add bindings for the MediaTek Dynamic Voltage and Frequency Scaling
>>> Resource Collector (DVFSRC), a hardware module used to collect all the
>>> requests from both software and the various remote processors embedded
>>> into the SoC and decide about a minimum operating voltage and a minimum
>>> DRAM frequency to fulfill those requests in an effort to provide the
>>> best achievable performance per watt.
>>>
>>> This hardware IP is capable of transparently performing direct register
>>> R/W on all of the DVFSRC-controlled regulators and SoC bandwidth knobs.
>>>
>>> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
>>> ---
>>>   .../soc/mediatek/mediatek,mt8183-dvfsrc.yaml  | 57 +++++++++++++++++++
>>>   1 file changed, 57 insertions(+)
>>>   create mode 100644 Documentation/devicetree/bindings/soc/mediatek/mediatek,mt8183-dvfsrc.yaml
>>>
>>> diff --git a/Documentation/devicetree/bindings/soc/mediatek/mediatek,mt8183-dvfsrc.yaml b/Documentation/devicetree/bindings/soc/mediatek/mediatek,mt8183-dvfsrc.yaml
>>> new file mode 100644
>>> index 000000000000..12bcc3fdfd07
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/soc/mediatek/mediatek,mt8183-dvfsrc.yaml
>>> @@ -0,0 +1,57 @@
>>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/soc/mediatek/mediatek,mt8183-dvfsrc.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: MediaTek Dynamic Voltage and Frequency Scaling Resource Collector (DVFSRC)
>>> +
>>> +description:
>>> +  The Dynamic Voltage and Frequency Scaling Resource Collector (DVFSRC) is a
>>> +  Hardware module used to collect all the requests from both software and the
>>> +  various remote processors embedded into the SoC and decide about a minimum
>>> +  operating voltage and a minimum DRAM frequency to fulfill those requests in
>>> +  an effort to provide the best achievable performance per watt.
>>> +  This hardware IP is capable of transparently performing direct register R/W
>>> +  on all of the DVFSRC-controlled regulators and SoC bandwidth knobs.
>>> +
>>> +maintainers:
>>> +  - AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
>>> +  - Henry Chen <henryc.chen@...iatek.com>
>>> +
>>> +properties:
>>> +  compatible:
>>> +    oneOf:
>>> +      - items:
>>
>> This items should not be needed with the enum, right?
>>

Whoops. Yep items is not needed.

>>> +          - enum:
>>> +              - mediatek,mt8183-dvfsrc
>>> +              - mediatek,mt8195-dvfsrc
>>> +      - items:
>>> +          - const: mediatek,mt8192-dvfsrc
>>> +          - const: mediatek,mt8195-dvfsrc
>>> +
>>> +  reg:
>>> +    maxItems: 1
>>> +    description: DVFSRC common register address and length.
>>> +
>>> +patternProperties:
>>> +  "@[0-9a-f]+$":
>>> +    type: object
>>
>> Why is there no enforcement of what a child could be here?
> 
> Seems like you know exactly what the children are: regulators and an
> interconnect? What am I missing?
> 

I wasn't sure whether that would've been a good idea, given that there will
be more possible children in the future - as in - more drivers that need the
DVFSRC communication.

But anyway yes, for now, it's just the regulator and interconnect drivers.

>>
>>> +required:
>>> +  - compatible
>>> +  - reg
>>> +
>>> +additionalProperties: false
>>> +
>>> +examples:
>>> +  - |
>>> +    soc {
>>> +        #address-cells = <2>;
>>> +        #size-cells = <2>;
>>> +
>>> +        dvfsrc@...12000 {
>>
>> "dvfsrc" looks like something my (imaginary given allergies) cat would

(allergies: ugh, same here - feel you)

>> produce from sitting on my keyboard. Could you use full words for the
>> node name and make it something that attempts to be generic please?
>>

I'm not entirely sure that I can find a generic name for this... I wonder if
"remoteproc" could work - as this is a remote processor (a MCU, actually).

To give you context, this doesn't need firmware to be loaded, and does not have
any remoteproc driver.

Because then, I don't think that "performance-controller" would be correct,
even though I have this N.2 choice... ideas?

Cheers,
Angelo

>>> +            compatible = "mediatek,mt8195-dvfsrc";
>>> +            reg = <0 0x10012000 0 0x1000>;
>>> +        };
>>> +    };
>>> -- 
>>> 2.44.0
>>>
> 
>