linux-kernel - Re: [PATCH v2 2/3] dt-bindings: clock: add QCOM SM6125 display clock bindings

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Date:   Mon, 28 Feb 2022 10:23:19 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        phone-devel@...r.kernel.org
Cc:     ~postmarketos/upstreaming@...ts.sr.ht,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Martin Botka <martin.botka@...ainline.org>,
        Jami Kettunen <jami.kettunen@...ainline.org>,
        Pavel Dubrova <pashadubrova@...il.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] dt-bindings: clock: add QCOM SM6125 display clock
 bindings

On 27/02/2022 22:43, Dmitry Baryshkov wrote:
> On 27/02/2022 13:03, Krzysztof Kozlowski wrote:
>> On 26/02/2022 21:09, Marijn Suijten wrote:
>>> From: Martin Botka <martin.botka@...ainline.org>
>>>
>>> Add device tree bindings for display clock controller for
>>> Qualcomm Technology Inc's SM6125 SoC.
>>>
>>> Signed-off-by: Martin Botka <martin.botka@...ainline.org>
>>> ---
>>>   .../bindings/clock/qcom,dispcc-sm6125.yaml    | 87 +++++++++++++++++++
>>>   .../dt-bindings/clock/qcom,dispcc-sm6125.h    | 41 +++++++++
>>>   2 files changed, 128 insertions(+)
>>>   create mode 100644 Documentation/devicetree/bindings/clock/qcom,dispcc-sm6125.yaml
>>>   create mode 100644 include/dt-bindings/clock/qcom,dispcc-sm6125.h
>>>
>>> diff --git a/Documentation/devicetree/bindings/clock/qcom,dispcc-sm6125.yaml b/Documentation/devicetree/bindings/clock/qcom,dispcc-sm6125.yaml
>>> new file mode 100644
>>> index 000000000000..3465042d0d9f
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/clock/qcom,dispcc-sm6125.yaml
>>> @@ -0,0 +1,87 @@
>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>> +%YAML 1.2
>>> +---
>>> +$id: http://devicetree.org/schemas/clock/qcom,dispcc-sm6125.yaml#
>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>> +
>>> +title: Qualcomm Display Clock Controller Binding for SM6125
>>> +
>>> +maintainers:
>>> +  - Martin Botka <martin.botka@...ainline.org>
>>> +
>>> +description: |
>>> +  Qualcomm display clock control module which supports the clocks and
>>> +  power domains on SM6125.
>>> +
>>> +  See also:
>>> +    dt-bindings/clock/qcom,dispcc-sm6125.h
>>> +
>>> +properties:
>>> +  compatible:
>>> +    enum:
>>> +      - qcom,sm6125-dispcc
>>> +
>>> +  clocks:
>>> +    items:
>>> +      - description: Board XO source
>>> +      - description: Byte clock from DSI PHY0
>>> +      - description: Pixel clock from DSI PHY0
>>> +      - description: Pixel clock from DSI PHY1
>>> +      - description: Link clock from DP PHY
>>> +      - description: VCO DIV clock from DP PHY
>>> +      - description: AHB config clock from GCC
>>> +
>>> +  clock-names:
>>> +    items:
>>> +      - const: bi_tcxo
>>> +      - const: dsi0_phy_pll_out_byteclk
>>> +      - const: dsi0_phy_pll_out_dsiclk
>>> +      - const: dsi1_phy_pll_out_dsiclk
>>> +      - const: dp_phy_pll_link_clk
>>> +      - const: dp_phy_pll_vco_div_clk
>>> +      - const: cfg_ahb_clk
>>> +
>>> +  '#clock-cells':
>>> +    const: 1
>>> +
>>> +  '#power-domain-cells':
>>> +    const: 1
>>> +
>>> +  reg:
>>> +    maxItems: 1
>>> +
>>> +required:
>>> +  - compatible
>>> +  - reg
>>> +  - clocks
>>> +  - clock-names
>>> +  - '#clock-cells'
>>> +  - '#power-domain-cells'
>>> +
>>> +additionalProperties: false
>>> +
>>> +examples:
>>> +  - |
>>> +    #include <dt-bindings/clock/qcom,rpmcc.h>
>>> +    #include <dt-bindings/clock/qcom,gcc-sm6125.h>
>>> +    clock-controller@...0000 {
>>> +      compatible = "qcom,sm6125-dispcc";
>>> +      reg = <0x5f00000 0x20000>;
>>> +      clocks = <&rpmcc RPM_SMD_XO_CLK_SRC>,
>>> +               <&dsi0_phy 0>,
>>> +               <&dsi0_phy 1>,
>>> +               <0>,
>>
>> This does not look like a valid phandle. This clock is required, isn't it?
> 
> Not, it's not required for general dispcc support.
> dispcc uses DSI and DP PHY clocks to provide respective pixel/byte/etc 
> clocks. However if support for DP is not enabled, the dispcc can work 
> w/o DP phy clock. Thus we typically add 0 phandles as placeholders for 
> DSI/DP clock sources and populate them as support for respective 
> interfaces gets implemented.
> 

Then the clock is optional, isn't it? While not modeling it as optional?


Best regards,
Krzysztof