FS-Boot in PetaLinux is a first stage boot loader demo for MicroBlaze™ platform only. It is to demonstrate how to load images from flash to the memory and jump to it. If you want to try FS-Boot, you must have a minimum of 8 KB block RAM.
FS-Boot supports parallel flash and SPI flash in standard SPI mode and Quad SPI mode only.
In order for FS-Boot to know where in the flash should get the image,
macro CONFIG_FS_BOOT_START needs to be defined. This is
done by the PetaLinux tools. PetaLinux tools set this macro automatically from the
boot partition settings in the menuconfig primary
flash partition table settings. For parallel flash, it is the start address of boot
partition. For SPI flash, it is the start offset of boot
partition.
The image in the flash requires a wrapper header followed by a BIN file. FS-Boot gets the target memory location from wrapper. The wrapper needs to contain the following information:
| Offset | Description | Value |
|---|---|---|
| 0×0 | FS-Boot bootable image magic code |
×0b8b40008 |
| 0×4 | BIN image size | User-defined |
| 0×100 | FS-Boot bootable image target memory address | User-defined. The PetaLinux tool automatically calculates it from the U-Boot text base address offset from the Memory Settings from the menuconfig. |
| 0×10c | Where the BIN file start | None |
The FS-Boot supports symmetric multi processing (SMP) from the 2020.1 release onwards. You can have multiple MicroBlaze processors in your design. A maximum of eight cores is supported.
The same FS-Boot which is built as part of the petalinux-build/petalinux-build -c fsboot works for all the cores. XSDB is
needed to flash the FS-Boot on all the cores. The following is an example for four
cores. xsdb > ta lists all the available cores. To boot your target
with SMP support, follow these steps:
<plnx-tool>/tools/xsct/bin/xsdb
xsdb > connect -url <target-url>
xsdb > fpga -f <plnx-proj-root>/images/linux/system.bit
xsdb > ta
xsdb > ta <core number>
xsdb > dow -f <plnx-proj-root>/images/linux/fs-boot.elf
the above two steps for all available cores.
xsdb > dow -f <plnx-proj-root>/images/linux/u-boot.elf
xsdb > dow -f <plnx-proj-root>/images/linux/image.ub