linux-kernel - Re: [PATCH 1/3] dt-bindings: display/msm: Add binding for SC8280XP MDSS

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Date:   Thu, 11 Aug 2022 10:56:06 +0300
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] dt-bindings: display/msm: Add binding for SC8280XP
 MDSS

On 11/08/2022 07:01, Bjorn Andersson wrote:
> Add binding for the display subsystem and display processing unit in the
> Qualcomm SC8280XP platform.
> 
> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> ---
>  .../bindings/display/msm/dpu-sc8280xp.yaml    | 284 ++++++++++++++++++
>  1 file changed, 284 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/msm/dpu-sc8280xp.yaml
> 
> diff --git a/Documentation/devicetree/bindings/display/msm/dpu-sc8280xp.yaml b/Documentation/devicetree/bindings/display/msm/dpu-sc8280xp.yaml
> new file mode 100644
> index 000000000000..6c25943e639c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/msm/dpu-sc8280xp.yaml

qcom prefix is needed (also when file is in msm subdir)

The file name should be based on compatible, so "qcom,sc8280xp-mdss.yaml"

> @@ -0,0 +1,284 @@
> +# SPDX-License-Identifier: GPL-2.0-only or BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/msm/dpu-sc8280xp.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Qualcomm Display Processing Unit for SC8280XP
> +
> +maintainers:
> +  - Bjorn Andersson <bjorn.andersson@...aro.org>
> +
> +description:
> +  Device tree bindings for MSM Mobile Display Subsystem (MDSS) that encapsulates
> +  sub-blocks like DPU display controller, DSI and DP interfaces etc. Device tree
> +  bindings of MDSS and DPU are mentioned for SC8280XP.

s/Device tree bindings//
so just:

SC8280XP MSM Mobile Display Subsystem (MDSS) that encapsulates
sub-blocks like DPU display controller, DSI and DP interfaces etc.

> +
> +properties:
> +  compatible:
> +    const: qcom,sc8280xp-mdss
> +
> +  reg:
> +    maxItems: 1
> +
> +  reg-names:
> +    const: mdss

You do not need reg names for one item, especially if the name is kind
of obvious... unless you re-use existing driver which needs it? Then
maybe let's change the driver to take first element?

> +
> +  power-domains:
> +    maxItems: 1
> +
> +  clocks:
> +    items:
> +      - description: Display AHB clock from gcc
> +      - description: Display AHB clock from dispcc
> +      - description: Display core clock
> +
> +  clock-names:
> +    items:
> +      - const: iface
> +      - const: ahb
> +      - const: core
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  interrupt-controller: true
> +
> +  "#address-cells": true
> +
> +  "#size-cells": true

I see other DPU bindings also specify both as "true". Why not a fixed
number (const)?

> +
> +  "#interrupt-cells":
> +    const: 1
> +
> +  iommus:
> +    items:
> +      - description: Phandle to apps_smmu node with SID mask for Hard-Fail port0
> +
> +  ranges: true
> +
> +  interconnects:
> +    minItems: 2

No need for minItems in such case.

> +    maxItems: 2
> +
> +  interconnect-names:
> +    items:
> +      - const: mdp0-mem
> +      - const: mdp1-mem
> +
> +  resets:
> +    items:
> +      - description: MDSS_CORE reset
> +
> +patternProperties:
> +  "^display-controller@[0-9a-f]+$":
> +    type: object
> +    description: Node containing the properties of DPU.

additionalProperties:false on this level

which will point to missing properties (e.g. opp-table)

> +
> +    properties:
> +      compatible:
> +        const: qcom,sc8280xp-dpu
> +


Best regards,
Krzysztof