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[FAQ] DRA829V: How do I find documentation for Linux Kernel device tree files

Genius 17420 points

Replies: 1

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Part Number: DRA829V

There are lot of properties defined in various nodes of Linux Kernel device tree files (*.dts, *.dtsi), where can I find more information about these nodes and properties.

  • In general all the device tree documentation is captured in Linus Kernel documentation folder - Documentation/devicetree/bindings/

    Below is an example on how to find the devicetree documentation file and the corresponding driver by using the compatible field of a node.

    MMC node:

            main_sdhci0: sdhci@4f80000 {
                    compatible = "ti,j721e-sdhci-8bit";
                    reg = <0x0 0x4f80000 0x0 0x1000>, <0x0 0x4f88000 0x0 0x400>;
                    interrupts = <GIC_SPI 3 IRQ_TYPE_LEVEL_HIGH>;
                    power-domains = <&k3_pds 91 TI_SCI_PD_EXCLUSIVE>;
                    clock-names = "clk_xin", "clk_ahb";
                    clocks = <&k3_clks 91 1>, <&k3_clks 91 0>;
                    assigned-clocks = <&k3_clks 91 1>;
                    assigned-clock-parents = <&k3_clks 91 2>;
                    bus-width = <8>;
                    mmc-ddr-1_8v;
                    ti,otap-del-sel-legacy = <0x0>;
                    ti,otap-del-sel-mmc-hs = <0x0>;
                    ti,otap-del-sel-ddr52 = <0x5>;
                    ti,otap-del-sel-hs200 = <0x6>;
                    ti,otap-del-sel-hs400 = <0x0>;
                    ti,trm-icp = <0x8>;
                    ti,strobe-sel = <0x77>;
                    dma-coherent;
            };

    Identifying the devicetree documentation:

    Looking for the compatible string in the Documentation folder will help in finding the documentation associated with this node.
    In this example, sdhci-am654.txt file will have details of the properties used in this node.

    ti-linux-kernel$ git grep "ti,j721e-sdhci-8bit" Documentation/devicetree/bindings/
    Documentation/devicetree/bindings/mmc/sdhci-am654.txt: "ti,j721e-sdhci-8bit": 8 bit SDHCI on J721E device.
    Documentation/devicetree/bindings/mmc/sdhci-am654.txt: ti,j721e-sdhci-8bit,


    Identifying the Kernel driver associated:

    Looking for the same compatible field in the driver folder will help in identifying the driver associated with the node.
    In this example, sdhci_am654.c is the driver associated with this node.

    ti-linux-kernel$ git grep "ti,j721e-sdhci-8bit" drivers/
    drivers/mmc/host/sdhci_am654.c: .compatible = "ti,j721e-sdhci-8bit",

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