OpenSBI Device Tree Configuration Guideline

Some configurations of OpenSBI's Generic Platform can be described in the device tree (DT) blob (or flattened device tree) passed to the OpenSBI firmwares by the previous booting stage. OpenSBI will parse and use these configurations during the boot phase, but delete them from the device tree at the end of cold boot.

OpenSBI Configuration Node

All nodes related to OpenSBI configuration should be under the OpenSBI configuration DT node. The /chosen DT node is the preferred parent of the OpenSBI configuration DT node.

The DT properties of a domain configuration DT node are as follows:

• compatible (Mandatory) - The compatible string of the OpenSBI configuration. This DT property should have value “opensbi,config”

• cold-boot-harts (Optional) - If a platform lacks an override cold_boot_allowed() mechanism, this DT property specifies that a set of harts is permitted to perform a cold boot. Otherwise, all harts are allowed to cold boot.

The OpenSBI Configuration Node will be deleted at the end of cold boot (replace the node (subtree) with nop tags).

Example

    chosen {
        opensbi-config {
            compatible = "opensbi,config";
            cold-boot-harts = <&cpu1 &cpu2 &cpu3 &cpu4>;
        };
    };

    cpus {
        #address-cells = <1>;
        #size-cells = <0>;
        timebase-frequency = <10000000>;

        cpu0: cpu@0 {
            device_type = "cpu";
            reg = <0x00>;
            compatible = "riscv";
            ...
        };

        cpu1: cpu@1 {
            device_type = "cpu";
            reg = <0x01>;
            compatible = "riscv";
            ...
        };

        cpu2: cpu@2 {
            device_type = "cpu";
            reg = <0x02>;
            compatible = "riscv";
            ...
        };

        cpu3: cpu@3 {
            device_type = "cpu";
            reg = <0x03>;
            compatible = "riscv";
            ...
        };

        cpu4: cpu@4 {
            device_type = "cpu";
            reg = <0x04>;
            compatible = "riscv";
            ...
        };
    };

    uart1: serial@10011000 {
        ...
    };