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 00:43:23 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        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 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.

> 
> 
> Best regards,
> Krzysztof


-- 
With best wishes
Dmitry