高通平台8953 Linux DTS(Device Tree Source)設備樹詳解之三(高通MSM8953 android7.1實例分析篇)

在前兩篇中我們了解了DTS的背景基礎知識以及發揮作用的流程，這篇文章我們以android 7.1 高通的MSM8953平台為例來添加一個基礎的i2c設備（包含一個gpio中斷）。

1，首先我們在該i2c設備的驅動中找到了匹配設備與驅動程序的compatible

 

static const struct of_device_id iqs263_of_match[] = {
    { .compatible = "azopteq,iqs263", },
    { },
};

2，由此compatible可以找到dts中對應的設備

 

kernel\arch\arm64\boot\dts\qcom\msm8953-mtp.dts

 

&i2c_8 { /* BLSP2 QUP4 */
    iqs263@44 { //Capacitive Touch Controller Driver
        compatible = "azopteq,iqs263";
        reg = <0x44>;

        pinctrl-names = "default";
        pinctrl-0 = <&iqs263_irq_config>;

        vdd-supply = <&pm8953_l5>;
        vio-supply = <&pm8953_l5>;
        interrupt-parent = <&tlmm>;
        interrupts = <48 0x2>;
        azopteq,irq-gpio =<&tlmm 48 0x2>;
    };
};

 

2.1，其中compatible屬性標識的名字是與驅動程序中名字相匹配的

2.2，其中reg屬性及@符號后的十六進制數字標識了該設備iqs263的i2c地址為0x44

2.3，&i2c_8前的&表明此處僅僅是對i2c_8節點的補充，我們可以找到該節點定義的地方

kernel\arch\arm64\boot\dts\qcom\msm8953.dtsi

 

&soc {
    i2c_8: i2c@7af8000 { /* BLSP2 QUP4 */
        compatible = "qcom,i2c-msm-v2";
        #address-cells = <1>;
        #size-cells = <0>;
        reg-names = "qup_phys_addr";
        reg = <0x7af8000 0x600>;
        interrupt-names = "qup_irq";
        interrupts = <0 302 0>;
        qcom,clk-freq-out = <400000>;
        qcom,clk-freq-in  = <19200000>;
        clock-names = "iface_clk", "core_clk";
        clocks = <&clock_gcc clk_gcc_blsp2_ahb_clk>,
            <&clock_gcc clk_gcc_blsp2_qup4_i2c_apps_clk>;

        pinctrl-names = "i2c_active", "i2c_sleep";
        pinctrl-0 = <&i2c_8_active>;
        pinctrl-1 = <&i2c_8_sleep>;
        qcom,noise-rjct-scl = <0>;
        qcom,noise-rjct-sda = <0>;
        qcom,master-id = <84>;
        dmas = <&dma_blsp2 10 64 0x20000020 0x20>,
            <&dma_blsp2 11 32 0x20000020 0x20>;
        dma-names = "tx", "rx";
    };
    rpm_bus: qcom,rpm-smd {
        compatible = "qcom,rpm-smd";
        rpm-channel-name = "rpm_requests";
        rpm-channel-type = <15>; /* SMD_APPS_RPM */
    };

這當中的大部分屬性都與平台相關了，可以看到定義了該i2c接口的時鍾源、中斷格式等。這部分一般由平台提供，作為驅動工程師了解即可。

 

2.3.1，i2c_8節點中的pinctrl-0指向了定義其io口的節點i2c_8_active和i2c_8_sleep，代碼如下可見該i2c的IO口為Gpio98和Gpio99

kernel\arch\arm64\boot\dts\qcom\msm8953-pinctrl.dtsi

 

&soc {
    tlmm: pinctrl@1000000 {
        i2c_8 {
            i2c_8_active: i2c_8_active {
                /* active state */
                mux {
                    pins = "gpio98", "gpio99";
                    function = "blsp_i2c8";
                };

                config {
                    pins = "gpio98", "gpio99";
                    drive-strength = <2>;
                    bias-disable;
                };
            };

            i2c_8_sleep: i2c_8_sleep {
                /* suspended state */
                mux {
                    pins = "gpio98", "gpio99";
                    function = "gpio";
                };

                config {
                    pins = "gpio98", "gpio99";
                    drive-strength = <2>;
                    bias-disable;
                };
            };
        };

        iqs263_irq_config: iqs263_irq_config {
            mux {
                pins = "gpio48";
                function = "gpio";
            };

            config {
                pins = "gpio48";
                drive-strength = <2>;
                bias-pull-up;
            };
        };

 

2.4，iqs263節點中的pinctrl-0 屬性指向了表明其io口屬性的節點為iqs263_irq_config，相關代碼也在2.3.1指示的msm8953-pinctrl.dtsi文件中。

其中定義了iqs263的中斷IO腳為Gpio48

 

2.5，iqs263節點中的vdd-supply，vio-supply屬性指示了表明iqs263芯片供電的引腳的節點pm8953_l5，代碼如下

kernel\arch\arm64\boot\dts\qcom\msm8953-regulator.dtsi

 

&rpm_bus {
    rpm-regulator-ldoa5 {
        status = "okay";
        pm8953_l5: regulator-l5 {
            regulator-min-microvolt = <1800000>;
            regulator-max-microvolt = <1800000>;
            qcom,init-voltage = <1800000>;
            status = "okay";
        };
    };

2.6，iqs263的interrupts = <48 0x2>屬性表明中斷號為48,2代表下降沿觸發。相關知識可以參考： 高通平台8953 Linux DTS(Device Tree Source)設備樹詳解之二（DTS設備樹匹配過程）

 

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