mirror of
https://github.com/riscv-software-src/opensbi
synced 2025-10-31 12:08:24 +00:00
a4555e5698
This updates documentation to describe parameters passed to firmware from previous booting stage, and corresponding address alignment requirement. This also fixes a typo in fw_dynamic.md (it's => its). Signed-off-by: Bin Meng <bmeng.cn@gmail.com> Reviewed-by: Anup Patel <anup.patel@wdc.com>
37 lines
1.6 KiB
Markdown
37 lines
1.6 KiB
Markdown
OpenSBI Firmware with Dynamic Information (FW_DYNAMIC)
|
|
======================================================
|
|
|
|
OpenSBI **firmware with dynamic info (FW_DYNAMIC)** is a firmware which gets
|
|
information about next booting stage (e.g. a bootloader or an OS) and runtime
|
|
OpenSBI library options from previous booting stage.
|
|
|
|
The previous booting stage will pass information to *FW_DYNAMIC* by creating
|
|
*struct fw_dynamic_info* in memory and passing its address to *FW_DYNAMIC*
|
|
via *a2* register of RISC-V CPU. The address must be aligned to 8 bytes on
|
|
RV64 and 4 bytes on RV32.
|
|
|
|
A *FW_DYNAMIC* firmware is particularly useful when the booting stage executed
|
|
prior to OpenSBI firmware is capable of loading both the OpenSBI firmware and
|
|
the booting stage binary to follow OpenSBI firmware.
|
|
|
|
*FW_DYNAMIC* Compilation
|
|
------------------------
|
|
|
|
A platform can enable *FW_DYNAMIC* firmware using any of the following methods.
|
|
|
|
1. Specifying `FW_DYNAMIC=y` on the top level `make` command line.
|
|
2. Specifying `FW_DYNAMIC=y` in the target platform *config.mk* configuration
|
|
file.
|
|
|
|
The compiled *FW_DYNAMIC* firmware ELF file is named *fw_dynamic.elf*. It's
|
|
expanded image file is *fw_dynamic.bin*. Both files are created in the platform
|
|
specific build directory under the *build/platform/<platform_subdir>/firmware*
|
|
directory.
|
|
|
|
*FW_DYNAMIC* Firmware Configuration Options
|
|
-------------------------------------------
|
|
|
|
The *FW_DYNAMIC* firmware does not requires any platform specific configuration
|
|
parameters because all required information is passed by previous booting stage
|
|
at runtime via *struct fw_dynamic_info*.
|