docs/system/riscv: sifive_u: Update S-mode U-Boot image build instructions

Currently, the documentation outlines the process for building the
S-mode U-Boot image using `make menuconfig` and manual actions within
the menuconfig UI. However, this approach is fragile due to Kconfig
options potentially changing across different releases. For example,
CONFIG_OF_PRIOR_STAGE has been replaced by CONFIG_BOARD since v2022.01
release, and CONFIG_TEXT_BASE has been moved to the 'General setup'
menu from the 'Boot options' menu in v2024.01 release.

This update aims to make the S-mode U-Boot image build instructions
future-proof. It leverages the 'config' script provided in the U-Boot
source tree to edit the .config file, followed by a `make olddefconfig`.

Validated with U-Boot v2024.01 release.

Signed-off-by: Bin Meng <bmeng@tinylab.org>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20240104071523.273702-1-bmeng@tinylab.org>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
This commit is contained in:
Bin Meng 2024-01-04 15:15:23 +08:00 committed by Alistair Francis
parent 3ca78c0689
commit e0299f71b3

View File

@ -210,7 +210,7 @@ command line options with ``qemu-system-riscv32``.
Running U-Boot
--------------
U-Boot mainline v2021.07 release is tested at the time of writing. To build a
U-Boot mainline v2024.01 release is tested at the time of writing. To build a
U-Boot mainline bootloader that can be booted by the ``sifive_u`` machine, use
the sifive_unleashed_defconfig with similar commands as described above for
Linux:
@ -325,15 +325,10 @@ configuration of U-Boot:
$ export CROSS_COMPILE=riscv64-linux-
$ make sifive_unleashed_defconfig
$ make menuconfig
then manually select the following configuration:
* Device Tree Control ---> Provider of DTB for DT Control ---> Prior Stage bootloader DTB
and unselect the following configuration:
* Library routines ---> Allow access to binman information in the device tree
$ ./scripts/config --enable OF_BOARD
$ ./scripts/config --disable BINMAN_FDT
$ ./scripts/config --disable SPL
$ make olddefconfig
This changes U-Boot to use the QEMU generated device tree blob, and bypass
running the U-Boot SPL stage.
@ -352,17 +347,13 @@ It's possible to create a 32-bit U-Boot S-mode image as well.
$ export CROSS_COMPILE=riscv64-linux-
$ make sifive_unleashed_defconfig
$ make menuconfig
then manually update the following configuration in U-Boot:
* Device Tree Control ---> Provider of DTB for DT Control ---> Prior Stage bootloader DTB
* RISC-V architecture ---> Base ISA ---> RV32I
* Boot options ---> Boot images ---> Text Base ---> 0x80400000
and unselect the following configuration:
* Library routines ---> Allow access to binman information in the device tree
$ ./scripts/config --disable ARCH_RV64I
$ ./scripts/config --enable ARCH_RV32I
$ ./scripts/config --set-val TEXT_BASE 0x80400000
$ ./scripts/config --enable OF_BOARD
$ ./scripts/config --disable BINMAN_FDT
$ ./scripts/config --disable SPL
$ make olddefconfig
Use the same command line options to boot the 32-bit U-Boot S-mode image: