linux-kernel - Re: [PATCH v2 2/3] dt-bindings: opp: Add v2-qcom-adreno vendor bindings

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Message-ID: <mz4zpcr4tqh2w7vt75f4ofxjzfve54ozzgpdbi2jjzk5pdxbk7@t36tlt3mmprt>
Date: Tue, 22 Oct 2024 07:49:40 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Akhil P Oommen <quic_akhilpo@...cinc.com>
Cc: Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>, 
	Konrad Dybcio <konradybcio@...nel.org>, Abhinav Kumar <quic_abhinavk@...cinc.com>, 
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, Marijn Suijten <marijn.suijten@...ainline.org>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>, Stephen Boyd <sboyd@...nel.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Bjorn Andersson <andersson@...nel.org>, 
	linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 2/3] dt-bindings: opp: Add v2-qcom-adreno vendor
 bindings

On Mon, Oct 21, 2024 at 05:23:43PM +0530, Akhil P Oommen wrote:
> Add a new schema which extends opp-v2 to support a new vendor specific
> property required for Adreno GPUs found in Qualcomm's SoCs. The new
> property called "qcom,opp-acd-level" carries a u32 value recommended
> for each opp needs to be shared to GMU during runtime.
> 
> Cc: Rob Clark <robdclark@...il.com>
> Signed-off-by: Akhil P Oommen <quic_akhilpo@...cinc.com>
> ---
>  .../bindings/opp/opp-v2-qcom-adreno.yaml           | 96 ++++++++++++++++++++++
>  1 file changed, 96 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/opp/opp-v2-qcom-adreno.yaml b/Documentation/devicetree/bindings/opp/opp-v2-qcom-adreno.yaml
> new file mode 100644
> index 000000000000..6d50c0405ef8
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/opp/opp-v2-qcom-adreno.yaml
> @@ -0,0 +1,96 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/opp/opp-v2-qcom-adreno.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Qualcomm Adreno compatible OPP supply
> +
> +description:
> +  Adreno GPUs present in Qualcomm's Snapdragon chipsets uses an OPP specific
> +  ACD related information tailored for the specific chipset. This binding
> +  provides the information needed to describe such a hardware value.
> +
> +maintainers:
> +  - Rob Clark <robdclark@...il.com>
> +
> +allOf:
> +  - $ref: opp-v2-base.yaml#
> +
> +properties:
> +  compatible:
> +    items:
> +      - const: operating-points-v2-adreno
> +      - const: operating-points-v2
> +
> +patternProperties:
> +  '^opp-?[0-9]+$':

'-' should not be optional. opp1 is not expected name.

> +    type: object
> +    additionalProperties: false
> +
> +    properties:
> +      opp-hz: true
> +
> +      opp-level: true
> +
> +      opp-peak-kBps: true
> +
> +      opp-supported-hw: true
> +
> +      qcom,opp-acd-level:
> +        description: |
> +          A positive value representing the ACD (Adaptive Clock Distribution,
> +          a fancy name for clk throttling during voltage droop) level associated
> +          with this OPP node. This value is shared to a co-processor inside GPU
> +          (called Graphics Management Unit a.k.a GMU) during wake up. It may not
> +          be present for some OPPs and GMU will disable ACD while transitioning
> +          to that OPP. This value encodes a voltage threshold and few other knobs
> +          which are identified by characterization of the SoC. So, it doesn't have
> +          any unit.

Thanks for explanation and other updates. I am still not happy with this
property. I do not see reason why DT should encode magic values in a
quite generic piece of code. This creates poor ABI, difficult to
maintain or understand.


> +        $ref: /schemas/types.yaml#/definitions/uint32
> +
> +    required:
> +      - opp-hz
> +      - opp-level
> +
> +required:
> +  - compatible
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/power/qcom-rpmpd.h>
> +
> +    gpu_opp_table: opp-table {
> +        compatible = "operating-points-v2-adreno", "operating-points-v2";
> +
> +        opp-687000000 {
> +                opp-hz = /bits/ 64 <687000000>;

Messed indentation.

Best regards,
Krzysztof