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docs: Add a payload section describing different payloads.

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Signed-off-by: Atish Patra <atish.patra@wdc.com>
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Atish Patra 2019-02-18 23:17:16 -08:00 • committed by Anup Patel
parent 3265310b05
commit 0db43770b3
4 changed files with 68 additions and 2 deletions
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2
README.md
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@ -135,7 +135,7 @@ A copy of this license with OpenSBI copyright can be found in the file
[COPYING.BSD].
All source files in OpenSBI contain the 2-Clause BSD license SPDX short
indentifier in place of the full license text.
identifier in place of the full license text.
```
SPDX-License-Identifier: BSD-2-Clause

19
docs/firmware/fw.md
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@ -5,7 +5,7 @@ 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
OpenSBI generic library code. The supported firmwares type 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.
@ -58,3 +58,20 @@ following documents.
[FW_JUMP]: fw_jump.md
[FW_PAYLOAD]: fw_payload.md
Providing different payloads to OpenSBI Firmware
------------------------------------------------
OpenSBI firmware can accept various payloads using a compile time option.
Typically, these payloads refer to the next stage boot loader (e.g. U-Boot)
or operating system kernel images (e.g. Linux). By default, OpenSBI
automatically provides a test payload if no specific payload is specified
at compile time.
To specify a payload at compile time, the make variable _FW_PAYLOAD_PATH_ is
used.
```
make PLATFORM=<platform_subdir> FW_PAYLOAD_PATH=<payload path>
```
The instructions to build each payload is different and the details can
be found in the
*docs/firmware/payload_<payload_name>.md* files.

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docs/firmware/payload_linux.md Normal file
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@ -0,0 +1,11 @@
Linux as a direct payload to OpenSBI
====================================
OpenSBI has the capability to load Linux kernel image directly in supervisor
mode. The flattened image generated by the Linux kernel build process can be
provided as payload to OpenSBI.
Detailed examples and platform guides can be found in both [QEMU](
../platform/qemu_virt.md) and [HiFive Unleashed](../platform/sifive_fu540.md)
platform guide respectively.

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docs/firmware/payload_uboot.md Normal file
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@ -0,0 +1,38 @@
U-Boot as a payload to OpenSBI
==============================
[U-Boot](https://www.denx.de/wiki/U-Boot) is an open-source primary boot loader.
It can be used as first and/or second stage boot loader in an embedded
environment. In the context of OpenSBI, U-boot can be specified as a payload to
OpenSBI firmware, becoming the boot stage following OpenSBI firmware
execution.
The current stable upstream code of U-boot does not yet include all patches
necessary to fully support OpenSBI. To use U-Boot as an OpenSBI payload, the
following out-of-tree patch series must be applied to the upstream U-Boot source
code.
HiFive Unleashed support for U-Boot
https://lists.denx.de/pipermail/u-boot/2019-February/358058.html
This patch series enables a single CPU to execute U-Boot. As a result, the next
stage boot code such as Linux kernel can also only execute a single CPU. U-Boot
SMP support for RISC-V can be enabled with the following additional patches.
https://lists.denx.de/pipermail/u-boot/2019-February/358393.html
Building and Generating U-Boot images
=====================================
Please refer to U-Boot build documentation for detailed instructions on how to build U-Boot images.
Once U-Boot images are built, Linux kernel image need to be converted to a format
that U-Boot understands.
```
<uboot-dir>/tools/mkimage -A riscv -O linux -T kernel -C none -a 0x80200000 -e 0x80200000 -n Linux -d \
<linux_build_directory>arch/riscv/boot/Image \
<linux_build_directory>/arch/riscv/boot/uImage
```
Copy the uImage to your tftpboot server path if network boot is required.