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SiFive FU540 SoC Platform

The FU540-C000 is the world’s first 4+1 64-bit RISC-V SoC from SiFive. The HiFive Unleashed development platform is based on FU540-C000 and capable of running Linux.

With QEMU v4.2 or above release, the 'sifive_u' machine can be used to test OpenSBI image built for the real hardware as well.

To build platform specific library and firmwares, provide the PLATFORM=generic parameter to the top level make command.

Platform Options

The SiFive FU540 SoC platform does not have any platform-specific options.

Building SiFive Fu540 Platform

In order to boot SMP Linux in U-Boot, Linux v5.1 (or higher) and latest U-Boot v2020.01 (or higher) should be used.

Linux Kernel Payload

The HiFive Unleashed device tree(DT) is merged in Linux v5.2 release. This DT (device tree) is not backward compatible with the DT passed from FSBL.

To use Linux v5.2 (or higher), the pre-built DTB (DT binary) from Linux v5.2 (or higher) should be used to build SiFive FU540 OpenSBI binaries by using the compile time option FW_FDT_PATH.

make PLATFORM=generic FW_PAYLOAD_PATH=<linux_build_directory>/arch/riscv/boot/Image
or
(For Linux v5.2 or higher)
make PLATFORM=generic FW_PAYLOAD_PATH=<linux_build_directory>/arch/riscv/boot/Image FW_FDT_PATH=<hifive-unleashed-a00.dtb path from Linux kernel>

U-Boot Payload

The command-line example here assumes that U-Boot was compiled using the sifive_fu540_defconfig configuration and with U-Boot v2020.01, and up to v2021.04. sifive_unleashed_defconfig shall be used with v2021.07 or above.

make PLATFORM=generic FW_PAYLOAD_PATH=<u-boot_build_dir>/u-boot-dtb.bin

For U-Boot v2020.07-rc4 or later releases, SPL support was added in U-Boot. Please refer to the detailed U-Boot booting guide available at U-Boot.

Flashing the OpenSBI firmware binary to storage media:

The first stage boot loader (FSBL) expects the storage media to have a GPT partition table. It tries to look for a partition with following GUID to load the next stage boot loader (OpenSBI in this case).

2E54B353-1271-4842-806F-E436D6AF6985

That's why the generated firmware binary in above steps should be copied to the partition of the sdcard with above GUID.

dd if=build/platform/generic/firmware/fw_payload.bin of=/dev/disk2s1 bs=1024

In my case, it is the first partition is disk2s1 that has been formatted with the above specified GUID.

In case of a brand new sdcard, it should be formatted with below partition tables as described here.

sgdisk --clear                                                               \
       --new=1:2048:67583  --change-name=1:bootloader --typecode=1:2E54B353-1271-4842-806F-E436D6AF6985   \
       --new=2:264192:     --change-name=2:root       --typecode=2:0FC63DAF-8483-4772-8E79-3D69D8477DE4 \
       ${DISK}

Booting SiFive Fu540 Platform

Linux Kernel Payload

As Linux kernel image is embedded in the OpenSBI firmware binary, HiFive Unleashed will directly boot into Linux directly after powered on.

U-Boot Payload

As U-Boot image is used as payload, HiFive Unleashed will boot into a U-Boot prompt. U-Boot tftp boot method can be used to load kernel image in U-Boot prompt. Here are the steps do a tftpboot.

  1. Set the ip address of the board.
setenv ipaddr <ipaddr of the board>
  1. Set the tftpboot server IP.
setenv serverip <ipaddr of the tftp server>
  1. Set the network gateway address.
setenv gatewayip <ipaddress of the network gateway>
  1. Load the Linux kernel image from the tftp server.
tftpboot ${kernel_addr_r} <Image path in tftpboot directory>
  1. Load the ramdisk image from the tftp server. This is only required if ramdisk is loaded from tftp server. This step is optional, if rootfs is already part of the kernel or loaded from an external storage by kernel.
tftpboot ${ramdisk_addr_r} <ramdisk path in tftpboot directory>
  1. Load the pre-compiled device tree via tftpboot.
tftpboot ${fdt_addr_r} <hifive-unleashed-a00.dtb path in tftpboot directory>
  1. Set the boot command-line arguments.
setenv bootargs "root=<root partition> rw console=ttySIF0 earlycon=sbi"

(Note: root partition should point to ** /dev/ram ** - If a ramdisk is used ** root=/dev/mmcblk0pX ** - If a rootfs is already on some other partition of sdcard) 8. Now boot into Linux.

booti ${kernel_addr_r} ${ramdisk_addr_r} ${fdt_addr_r}
or
(If ramdisk is not loaded from network)
booti ${kernel_addr_r} - ${fdt_addr_r}

U-Boot & Linux Kernel as a single payload

At U-Boot prompt execute the following boot command to boot Linux.

booti ${kernel_addr_r} - ${fdt_addr_r}

QEMU Specific Instructions

If you want to test OpenSBI with QEMU 'sifive_u' machine, please follow the same instructions above, with the exception of not passing FW_FDT_PATH.

This is because QEMU generates a device tree blob on the fly based on the command line parameters, and it's compatible with the one used in the upstream Linux kernel.

When U-Boot v2021.07 (or higher) is used as the payload, as the SiFive FU540 DTB for the real hardware is embedded in U-Boot binary itself, due to the same reason above, we need to switch the U-Boot sifive_unleashed_defconfig configuration from CONFIG_OF_SEPARATE to CONFIG_OF_PRIOR_STAGE so that U-Boot uses the DTB generated by QEMU, and u-boot.bin should be used as the payload image, like:

make PLATFORM=generic FW_PAYLOAD_PATH=<u-boot_build_dir>/u-boot.bin

U-Boot v2020.07 release added SPL support to SiFive HiFive Unleashed board, hence a build error will be seen after you switch to CONFIG_OF_PRIOR_STAGE.

./tools/mkimage: Can't open arch/riscv/dts/hifive-unleashed-a00.dtb: No such file or directory
./tools/mkimage: failed to build FIT
Makefile:1402: recipe for target 'u-boot.img' failed
make: *** [u-boot.img] Error 1

The above errors can be safely ignored as we don't run U-Boot SPL under QEMU.

Run:

qemu-system-riscv64 -M sifive_u -m 256M -nographic \
	-bios build/platform/generic/firmware/fw_payload.bin

or

qemu-system-riscv64 -M sifive_u -m 256M -nographic \
	-bios build/platform/generic/firmware/fw_jump.bin \
	-kernel <uboot_build_dir>/u-boot.bin

While the real hardware operates at the 64-bit mode, it's possible for QEMU to test the 32-bit OpenSBI firmware. This can be helpful for testing 32-bit SiFive specific drivers.