roms: opensbi: Add 32-bit firmware image for sifive_u machine

Although the real world SiFive HiFive Unleashed board is a 64-bit
hardware configuration, with QEMU it is possible to test 32-bit
configuration with the same hardware features.

This updates the roms Makefile to add the build rules for creating
the 32-bit OpenSBI firmware image for sifive_u machine. A pre-built
OpenSBI v0.6 image has been added as the default bios for 32-bit
sifive_u machine.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

Makefile

@@ -848,7 +848,7 @@ u-boot.e500 u-boot-sam460-20100605.bin \
 qemu_vga.ndrv \
 edk2-licenses.txt \
 hppa-firmware.img \
-opensbi-riscv32-virt-fw_jump.bin \
+opensbi-riscv32-sifive_u-fw_jump.bin opensbi-riscv32-virt-fw_jump.bin \
 opensbi-riscv64-sifive_u-fw_jump.bin opensbi-riscv64-virt-fw_jump.bin
 
 

roms/Makefile

@@ -66,6 +66,7 @@ default help:
 	@echo "  efi                -- update UEFI (edk2) platform firmware"
 	@echo "  opensbi32-virt     -- update OpenSBI for 32-bit virt machine"
 	@echo "  opensbi64-virt     -- update OpenSBI for 64-bit virt machine"
+	@echo "  opensbi32-sifive_u -- update OpenSBI for 32-bit sifive_u machine"
 	@echo "  opensbi64-sifive_u -- update OpenSBI for 64-bit sifive_u machine"
 	@echo "  bios-microvm       -- update bios-microvm.bin (qboot)"
 	@echo "  clean              -- delete the files generated by the previous" \
@@ -181,6 +182,12 @@ opensbi64-virt:
 		PLATFORM="qemu/virt"
 	cp opensbi/build/platform/qemu/virt/firmware/fw_jump.bin ../pc-bios/opensbi-riscv64-virt-fw_jump.bin
 
+opensbi32-sifive_u:
+	$(MAKE) -C opensbi \
+		CROSS_COMPILE=$(riscv32_cross_prefix) \
+		PLATFORM="sifive/fu540"
+	cp opensbi/build/platform/sifive/fu540/firmware/fw_jump.bin ../pc-bios/opensbi-riscv32-sifive_u-fw_jump.bin
+
 opensbi64-sifive_u:
 	$(MAKE) -C opensbi \
 		CROSS_COMPILE=$(riscv64_cross_prefix) \