This how-to describes how to build the u-boot bootloader for your target platform. Building the U-Boot bootloader is a part of the Xilinx design flow described in Getting Started. U-Boot depends upon an externally build device tree compiler (dtc) in order to build successfully. Please build the dtc tool before proceeding with the steps described below.

Task Dependencies (Pre-requisites)


Tools Required


Input Files Required

  • config.mk (MicroBlaze only)
  • xparameters.h (MicroBlaze only)

Output Files Produced

  • u-boot
  • mkimage

Task Description

All commands have to be executed in your u-boot source directory.
The first step is to configure the sources for the intended target. Xilinx u-boot supports the following targets:
Platform
U-Boot target
Zynq UltraScale+ MPSoC mini
xilinx_zynqmp_mini_defconfig
Zynq UltraScale+ MPSoC mini_emm0
xilinx_zynqmp_mini_emmc0_defconfig
Zynq UltraScale+ MPSoC mini_emm1
xilinx_zynqmp_mini_emmc1_defconfig
Zynq UltraScale+ MPSoC mini_nand
xilinx_zynqmp_mini_nand_defconfig
Zynq UltraScale+ MPSoC mini_qspi
xilinx_zynqmp_mini_qspi_defconfig
Zynq UltraScale+ MPSoC ZC1232
xilinx_zynqmp_zc1232_revA_defconfig
Zynq UltraScale+ MPSoC ZC1254
xilinx_zynqmp_zc1254_revA_defconfig
Zynq UltraScale+ MPSoC ZC1275
xilinx_zynqmp_zc1275_revB_defconfig
Zynq UltraScale+ MPSoC ZC1751_dc1
xilinx_zynqmp_zc1751_xm015_dc1_defconfig
Zynq UltraScale+ MPSoC ZC1751_dc2
xilinx_zynqmp_zc1751_xm016_dc2_defconfig
Zynq UltraScale+ MPSoC ZC1751_dc3
xilinx_zynqmp_zc1751_xm017_dc3_defconfig
Zynq UltraScale+ MPSoC ZC1751_dc4
xilinx_zynqmp_zc1751_xm018_dc4_defconfig
Zynq UltraScale+ MPSoC ZC1751_dc5
xilinx_zynqmp_zc1751_xm019_dc5_defconfig
Zynq UltraScale+ MPSoC ZCU100
xilinx_zynqmp_zcu100_revC_defconfig
Zynq UltraScale+ MPSoC ZCU102
xilinx_zynqmp_zcu102_rev1_0_defconfig
Zynq UltraScale+ MPSoC ZCU104
xilinx_zynqmp_zcu104_revC_defconfig
Zynq UltraScale+ MPSoC ZCU106
xilinx_zynqmp_zcu106_revA_defconfig
Zynq UltraScale+ MPSoC ZCU111
xilinx_zynqmp_zcu111_revA_defconfig
Zynq CC108
zynq_cc108_defconfig
Zynq cse_nand
zynq_cse_nand_defconfig
Zynq cse_nor
zynq_cse_nor_defconfig
Zynq cse_qspi
zynq_cse_qspi_defconfig
Zynq ZC702
zynq_zc702_defconfig
Zynq ZC702_RSA
zynq_zc702_RSA_defconfig
Zynq ZC706
zynq_zc706_defconfig
Zynq ZC770 DC1
zynq_zc770_xm010_defconfig
Zynq ZC770 DC2 with x8 NAND
zynq_zc770_xm011_defconfig
Zynq ZC770 DC2 with x16 NAND
zynq_zc770_xm011_x16_defconfig
Zynq ZC770 DC3
zynq_zc770_xm012_defconfig
Zynq ZC770 DC4
zynq_zc770_xm013_defconfig
Zynq Zed Board
zynq_zed_defconfig
Microblaze Board
microblaze-generic_defconfig

To build U-Boot for ZC702 execute:
make zynq_zc702_defconfig
make
To build U-Boot for ZCU102 execute:
make xilinx_zynqmp_zcu102_rev1_0_defconfig
make
After the build process completes the target u-boot elf-file is created in the top level source directory, named 'u-boot'. Additionally in the tools/ directory the 'mkimage' utility is created, which is used in other tasks to wrap images into u-boot format.
To make mkimage available in other steps, it is recommended to add the tools directory to your $PATH.
cd tools
export PATH=`pwd`:$PATH

U-Boot for MicroBlaze

The Xilinx U-Boot project is based on the source code from git:git.denx.de

The devices that have been tested include UART lite, UART 16550, Linear flash, EMAC lite, LL TEMAC with PLB DMA, and AXI EMAC with AXI DMA. The timer counter and interrupt controller were also tested.
Tests were done on Spartan 605 (PLB and AXI) and Kintex 705 (AXI) evaluation platforms using XPS 14.2 and 14.3.

The hardware project

Typical
Make sure the following peripherals are included in the system:
Name
Value
MicroBlaze processor configured for (Low-end) Linux with MMU
microblaze cpu
serial
uartlite or uart16550
external memory controller
ddr or sdram
intc
interrupt controller
timer
timer with interrupts

Optional
U-Boot includes capabilities of writing to/reading from flash and also transferring files over a network if the available hardware is present:
flash
NOR flash
spi
spi/qspi flashes
i2c
i2c controller
ethernet lite
EMAC lite
ethernet
AXI EMAC with AXI DMA
Additional peripherals and features are considered outside the scope of this page.

Building U-Boot

There are two ways to compile u-boot for Microblaze board.
1. OSL flow to compile u-boot
The U-Boot source tree can be downloaded from the Xilinx Git server. The repository is u-boot-xlnx and the branch is master:
git clone https://github.com/Xilinx/u-boot-xlnx.git
The U-Boot compilation will use the definitions and flags defined in config.mk and xparameters.h . Import these two files generated by the petalinux project into the U-Boot directory for MicroBlaze
cp <plnx-proj-root>/components/plnx_workspace/fsboot/fsboot/mba_fs_boot_bsp/microblaze_0/include/xparameters.h  <u-boot-xlnx>/board/xilinx/microblaze-generic/
cp <plnx-proj-root>/project-spec/meta-plnx-generated/recipes-bsp/u-boot/configs/config.mk   <u-boot-xlnx>/board/xilinx/microblaze-generic/
Rename platform-auto.h to microblaze-generic.h
<plnx-proj-root>/project-spec/meta-plnx-generated/recipes-bsp/u-boot/configs/platform-auto.h
After renaming, copy microblaze-generic.h to the u-boot-xlnx/include/configs
cp <plnx-proj-root>/project-spec/meta-plnx-generated/recipes-bsp/u-boot/configs/microblaze-generic.h  u-boot-xlnx/include/configs/
Replace the dts file of u-boot-xlnx via petalinux project
Convert the .dtb file into .dts file in petalinux project
dtc -I dtb -O dts -o <plnx-proj-root>/components/plnx_workspace/device-tree/device-tree-generation/plnx_microblaze-system.dts
Renamed this generated dts file to microblaze-generic.dts and copy it to the u-boot-xlnx
<plnx-proj-root>/components/plnx_workspace/device-tree/device-tree-generation/microblaze-generic.dts
cp <plnx-proj-root>/components/plnx_workspace/device-tree/device-tree-generation/microblaze-generic.dts u-boot-xlnx/arch/microblaze/dts
Go into the u-boot-xilinx top directory and run the following commands in bash to compile the u-boot
make distclean
export CROSS_COMPILE=microblazeel-xilinx-linux-gnu-
export ARCH=microblazeel
make microblaze-generic_defconfig
scripts/kconfig/merge_config.sh -m .config  <plnx-proj-root >/project-spec/meta-plnx-generated/recipes-bsp/u-boot/configs/config.cfg
make

Loading and running U-Boot

Downloading U-Boot to MicroBlaze
Once the bitstream containing at least a minimally configured hardware system has been downloaded to the FPGA, XMD is used to download the cross-compiled U-Boot to the MicroBlaze soft processor:
XMD> connect mb mdm
XMD> dow <u-boot-xlnlx>/build/u-boot
XMD> run
U-Boot commands
The list of U-boot commands can be accessed while in the U-Boot prompt. Type "help" or "?" for a complete listing of available commands.

Documentation on U-Boot may be found at http://www.denx.de/wiki/DULG/Manual .

Running Linux using U-Boot

Preparing the Linux images for U-Boot
Specific details on building the kernel for MicroBlaze are contained in the Build Kernel page.
Instructions to obtain a root filesystem can be found at the Build and Modify a Root File System page.

The kernel and the root filesystem must be wrapped with a U-Boot header in order for U-Boot to accept these files. The mkimage utility is used for this purpose, however, it is not part of the MicroBlaze GNU tools. It is part of U-Boot itself and if U-Boot has been compiled as specified on this page, it will be found under <u-boot-xlnx>/build/tools/ .

When building linux.bin, as explained in the Build Kernel page, the kernel build process automatically creates an additional image, with the ".ub" suffix. linux.bin.ub is the Linux binary image wrapped with a U-Boot header. The Linux compilation process will automatically invoke mkimage, therefore, it is important to include the path to the U-Boot tools in the PATH environment variable.

The root filesystem also needs to be wrapped with a U-Boot header as follows:
mkimage -A microblaze -O linux -T ramdisk -C gzip -d ramdisk.image.gz uramdisk.image.gz

Booting Linux
XMD or TFTP may be used to download Linux to the FPGA (memory). U-Boot can then use these files to boot Linux. Once the kernel, root filesystem, and device tree images are present in memory, the command to boot Linux is:
U-Boot> bootm <addr of kernel> <addr of rootfs> <addr of device tree blob (dtb)>

Note: Make sure the kernel and root filesystem images are wrapped by with the U-Boot header. The device tree blob does not need to be wrapped with the U-Boot header.

Creating the BSP required by U-Boot (Unverified)
This is old BSP and doesn't tested with latest u-boot.
To build U-Boot correctly, some information about the system will need to be provided to the U-Boot build tree. This information is generated by the U-Boot BSP.

First, download the U-Boot BSP source Once it has been installed and the project has been exported to SDK, the U-Boot BSP can be created for the system.

In order for the U-Boot BSP to generate the necessary settings for U-Boot, it needs to know which specific peripherals should be used for some corresponding tasks. These selections are made in the fields/drop-down menus located in the 'Settings' of the newly created U-Boot BSP. For example:
Name
Value
stdout
rs232_uart_1
stdin
rs232_uart_1
main_memory
ddr2_sdram
flash_memory
flash
ethernet
hard_ethernet_mac
timer
xps_timer_0
Once the U-Boot BSP has been compiled in SDK, the generated files, config.mk and xparameters.h, can be found at <sdk_workspace>/uboot_bsp_0/microblaze_0/libsrc/uboot_v*/ .

Downloading the source tree
The U-Boot source tree can be downloaded from the Xilinx Git server. The repository is u-boot-xlnx and the branch is master:
linux-host> git clone git://github.com/Xilinx/u-boot-xlnx.git
linux-host> cd u-boot-xlnx
Compiling U-Boot
The U-Boot compilation will use the definitions and flags defined in config.mk and xparameters.h . Import these two files generated by the U-Boot BSP in SDK into the U-Boot directory for MicroBlaze located at <u-boot-xlnx>/board/xilinx/microblaze-generic/ .
[[code]]
Xilinx's MicroBlaze GNU toolchain will be used to cross-compile U-Boot for MicroBlaze. Instructions on obtaining and setting up the newest cross-compilation toolchain for MicroBlaze may be found at [[MicroBlaze Gnu Tools|Microblaze GNU Tools]].

Now that U-Boot and the toolchain are configured correctly, we can cross-compile U-Boot:
linux-host> cd <u-boot-xlnx>
linux-host> export BUILD_DIR=$PWD/build
linux-host> make microblaze-generic_defconfig
linux-host> make

Build Steps


Related Links