diff options
| author | Damien Le Moal <damien.lemoal@wdc.com> | 2019-01-23 23:48:42 +0900 |
|---|---|---|
| committer | Anup Patel <anup@brainfault.org> | 2019-01-24 18:45:01 +0530 |
| commit | 808fe4b82a68fd0c99b3a4cc9185adba817e03d0 (patch) | |
| tree | 5e1bea5d7c85a93ff0d1a41598f771413231a590 /docs | |
| parent | e580b86a41f5c4f894cd042f7096603ac8eb108c (diff) | |
docs/firmware: Add top level document file
Provide an overview of all supported firmware files and point to each
firmware type documentation file.
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/firmware/fw.md | 60 |
1 files changed, 60 insertions, 0 deletions
diff --git a/docs/firmware/fw.md b/docs/firmware/fw.md new file mode 100644 index 0000000..2b6c26a --- /dev/null +++ b/docs/firmware/fw.md @@ -0,0 +1,60 @@ +OpenSBI Platform Firmwares +========================== + +OpenSBI provides firmware builds for specific platforms. Different types of +firmwares are supported to deal with the differences between different platforms +early boot stage. All firmwares will execute the same initialization procedure +of the platform hardware according to the platform specific code as well as +OpenSBI generic library code. The supported firmwares types will differ in how +the arguments passed by the platform early boot stage are handled, as well as +how the boot stage following the firmware will be handled and executed. + +OpenSBI currently supports two different types of firmwares. + +Firmware with Jump Address (*FW_JUMP*) +-------------------------------------- + +The *FW_JUMP* firmware only handles the address of the next booting stage +entry, e.g. a bootloader or an OS kernel, without directly including the +binary code for this next stage. + +A *FW_JUMP* 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. + +Firmware with Payload (*FW_PAYLOAD*) +------------------------------------ + +The *FW_PAYLOAD* firmware directly includes the binary code for the booting +stage to follow OpenSBI firmware execution. Typically, this payload will be a +bootloader or an OS kernel. + +A *FW_PAYLOAD* firmware is particularly useful when the booting stage executed +prior to OpenSBI firmware is not capable of loading both OpenSBI firmware and +the booting stage to follow OpenSBI firmware. + +A *FW_PAYLOAD* firmware is also useful for cases where the booting stage prior +to OpenSBI firmware does not pass a *flattened device tree (FDT file)*. In such +case, a *FW_PAYLOAD* firmware allows embedding a flattened device tree in the +.text section of the final firmware. + +Firmware Configuration and Compilation +-------------------------------------- + +All firmware types mandate the definition of the following compile time +configuration parameter. + +* **FW_TEXT_ADDR** - Defines the address at which the previous booting stage + loads OpenSBI firmware. + +Additionally, each firmware type as a set of type specific configuration +parameters. Detailed information for each firmware type can be found in the +following documents. + +* *[FW_JUMP]*: The *Firmware with Jump Address (FW_JUMP)* is described in more + details in the file *fw_jump.md*. +* *[FW_PAYLOAD]*: The *Firmware with Payload (FW_PAYLOAD)* is described in more + details in the file *fw_payload.md*. + +[FW_JUMP]: fw_jump.md +[FW_PAYLOAD]: fw_payload.md |