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

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Message-ID: <74afb676-4a85-7a8e-f7ea-20d8a0967d7d@linaro.org>
Date:   Thu, 11 Aug 2022 11:04:59 +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 10:56, Krzysztof Kozlowski wrote:
> 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?

OK, I see the driver expects this. It seems it is legacy from
87729e2a7871 ("drm/msm: unify MDSS drivers") times. So it could be
changed to grab first element always (older MDSS with three reg items
still has mdss_phys at first item).

> 
>> +
>> +  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)

I'll fix existing bindings which have similar issue.


Best regards,
Krzysztof