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docs: Add OpenSBI DT configuration guide.

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This patch add docs/opensbi_config.md which describes the
"/chosen/opensbi-config" DT node and properties

Signed-off-by: Cheng Yang <yangcheng.work@foxmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Cheng Yang
2024-02-08 11:14:33 +08:00
committed by Anup Patel
parent 67ce5a763c
commit 23e7e483ee
2 changed files with 84 additions and 0 deletions
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1
docs/doxygen.cfg
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@@ -796,6 +796,7 @@ INPUT = @@SRC_DIR@@/README.md \
@@SRC_DIR@@/docs/platform_requirements.md \
@@SRC_DIR@@/docs/library_usage.md \
@@SRC_DIR@@/docs/domain_support.md \
@@SRC_DIR@@/docs/opensbi_config.md \
@@SRC_DIR@@/docs/firmware \
@@SRC_DIR@@/docs/platform \
@@SRC_DIR@@/include \

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docs/opensbi_config.md Normal file
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@@ -0,0 +1,83 @@
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
```text
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 {
...
};
```