This article will discuss the steps needed to download and compile a Bootable (SD) Linux Image for the ZCU102 using the OSL flow.

Introduction

The recommended flow for building a Linux system is to use the Petalinux tools. However, this article offers an alternative for users that want full visibility into the Image.

This assumes that the users has downloaded Vitis (used to by the devcetree generator). I have structured this wiki in a way that users can copy this into their Makefile for ease of use. However, users will need to be careful of the makefile syntax while copy and pasting.
Some steps are duplicated. For example, the cross_compile steps. This is intentional to allow the users to build each image in isolation. However, users must use the same tag, as there are dependencies between pmufw and atf for example.

NOTE: If building on an Ubuntu (or derivative machine), ensure that the default shell has been changed from Dash to Bash. Compiling in Dash may result in syntax errors within the Makefile that will prevent the code from compiling.

Makefile params:

params

SHELL := /bin/bash
TOOLS ?= /proj/gsd/vivado/Vitis
VERSION ?= 2020.2
BOARD ?= ZCU102

Note: Make sure that the tools patch point to your relevant install on your machine

Getting Sources:

get_sources

get_sources:
	if [ ! -d "./bootgen" ];then \
		git clone https://github.com/Xilinx/bootgen; \
		$(MAKE) -C bootgen; \
	fi
	if [ ! -d "./linux-xlnx" ];then \
		git clone https://github.com/Xilinx/linux-xlnx; \
		cd linux-xlnx && git checkout xilinx-v$(VERSION); \
	fi
	if [ ! -d "./repo" ];then \
		mkdir -p repo/my_dtg; \
		cd repo/my_dtg && git clone https://github.com/Xilinx/device-tree-xlnx; \
		cd device-tree-xlnx && git checkout xilinx-v$(VERSION); \
	fi
	if [ ! -d "./u-boot-xlnx" ];then \
		git clone https://github.com/Xilinx/u-boot-xlnx; \
		cd u-boot-xlnx && git checkout xilinx-v$(VERSION); \
	fi
	if [ ! -d "./arm-trusted-firmware" ];then \
		git clone https://github.com/Xilinx/arm-trusted-firmware; \
		cd arm-trusted-firmware && git checkout xilinx-v$(VERSION); \
	fi
	if [ ! -d "./dtc" ];then \
		git clone https://git.kernel.org/pub/scm/utils/dtc/dtc.git; \
		$(MAKE) -C dtc; \
	fi
	if [ ! -d "./embeddedsw" ];then \
		git clone https://github.com/Xilinx/embeddedsw; \
		cd embeddedsw && git checkout xilinx-v$(VERSION); \
	fi

Build FSBL

Create, or append the proc below to your xsct_script.tcl

fsbl

proc fsbl {args} {
	set board 0
	for {set i 0} {$i < [llength $args]} {incr i} {
		if {[lindex $args $i] == "-board"} {
			set board [string toupper [lindex $args [expr {$i + 1}]]] 
		}
	}
	set xsa [glob -nocomplain -directory [pwd] -type f *.xsa *.hdf]
	hsi::open_hw_design $xsa
	if {[file isdirectory embeddedsw]} {
		puts "INFO: Adding embeddedsw repo"
		hsi::set_repo_path ./embeddedsw
	}
	set fsbl_design [hsi::create_sw_design fsbl_1 -proc psu_cortexa53_0 -app zynqmp_fsbl]
	if {$board != 0} {
		common::set_property -name APP_COMPILER_FLAGS -value "-DXPS_BOARD_${board}" -objects $fsbl_design
	}
	hsi::generate_app -dir zynqmp_fsbl -compile
	hsi::close_hw_design [hsi::current_hw_design]
}

Note: if you have a development board such as the ZCU102, then you can pass this as a symbol to the compiler

Then call this from your Makefile:

build_fsbl

fsbl:
	$(RM) -r zynqmp_fsbl
	$(TOOLS)/$(VERSION)/bin/xsct -eval "source xsct_script.tcl; fsbl -board $(BOARD)"

If users want to make modifications to the FSBL then they can do this in the embeddedsw/lib/sw_apps/zynqmp_fsbl/src. Or, if a valid patch then apply this to embeddedsw

Build PMU Firmware

Create, or append the proc below to your xsct_script.tcl

pmufw

proc pmufw {} {
	set xsa [glob -nocomplain -directory [pwd] -type f *.xsa *.hdf]
	hsi::open_hw_design $xsa
	if {[file isdirectory embeddedsw]} {
		puts "INFO: Adding embeddedsw repo"
		hsi::set_repo_path ./embeddedsw
	}
	hsi::generate_app -app zynqmp_pmufw -proc psu_pmu_0 -dir zynqmp_pmufw -compile
	hsi::close_hw_design [hsi::current_hw_design]
}

Then call this from your Makefile:

build_pmufw

pmufw:
	$(RM) -r zynqmp_pmufw
	$(TOOLS)/$(VERSION)/bin/xsct -eval "source xsct_script.tcl; pmufw"

If users want to make modifications to the PMUFW then they can do this in the embeddedsw/lib/sw_apps/zynqmp_pmufw/src. Or, if a valid patch then apply this to embeddedsw

Build ATF

atf

atf:
	$(MAKE) -C arm-trusted-firmware clean
	source $(TOOLS)/$(VERSION)/settings64.sh; \
	export CROSS_COMPILE=aarch64-none-elf-; \
	cd arm-trusted-firmware; \
	$(MAKE) -f Makefile DEBUG=0 PLAT=zynqmp bl31

Note: If users want to debug (ie use the symbols) the ATF in Vitis, then set the DEBUG=1. This will place the ATF in DDR at 0x1000. For more info see the ATF wiki here

Build u-boot

u-boot

uboot:
	$(MAKE) -C u-boot-xlnx clean
	source $(TOOLS)/$(VERSION)/settings64.sh; \
	export CROSS_COMPILE=aarch64-linux-gnu-; \
	export ARCH=aarch64; \
	export CC=aarch64-linux-gnu-gcc; \
	export PATH=$$PATH:$(shell pwd)/dtc; \
	cd u-boot-xlnx; \
	$(MAKE) xilinx_zynqmp_virt_defconfig; \
	$(MAKE) -f Makefile all -j 32

Note: If users want to debug (ie use the symbols) the u-boot in Vitis, then use the u-boot (renamed u-boot.elf) in the boot image.

Build Linux Image:

kernel

kernel:
	$(MAKE) -C linux-xlnx clean
	source $(TOOLS)/$(VERSION)/settings64.sh; \
	export CROSS_COMPILE=aarch64-linux-gnu-; \
	export ARCH=arm64; \
	export CC=aarch64-linux-gnu-gcc; \
	cd linux-xlnx; \
	$(MAKE) -f Makefile xilinx_zynqmp_defconfig; \
	$(MAKE) -f Makefile all -j 32; \
	$(MAKE) -f Makefile modules_install INSTALL_MOD_PATH=.

Build device-tree

Create a xsct_script.tcl file with the following contents:

proc build_dts {args} {
	set board 0
	set version 2020.2
	for {set i 0} {$i < [llength $args]} {incr i} {
		if {[lindex $args $i] == "-board"} {
			set board [string tolower [lindex $args [expr {$i + 1}]]] 
		}
		if {[lindex $args $i] == "-version"} {
			set version [string toupper [lindex $args [expr {$i + 1}]]] 
		}
	}
    	set xsa [glob -nocomplain -directory [pwd] -type f *.xsa]
    	hsi::open_hw_design $xsa
    	hsi::set_repo_path ./repo
    	hsi::create_sw_design device-tree -os device_tree -proc psu_cortexa53_0
    	hsi::generate_target -dir my_dts
    	hsi::close_hw_design [hsi::current_hw_design]
    	if {$board != 0} {
			foreach lib [glob -nocomplain -directory repo/my_dtg/device-tree-xlnx/device_tree/data/kernel_dtsi/${version}/include/dt-bindings -type d *] {
				if {![file exists my_dts/include/dt-bindings/[file tail $lib]]} {
					file copy -force $lib my_dts/include/dt-bindings
				}
			}
			set dtsi_files [glob -nocomplain -directory repo/my_dtg/device-tree-xlnx/device_tree/data/kernel_dtsi/${version}/BOARD -type f *${board}*]
			if {[llength $dtsi_files] != 0} {
				file copy -force [lindex $dtsi_files end] my_dts
				set fileId [open my_dts/system-user.dtsi "w"]
				puts $fileId "/include/ \"[file tail [lindex $dtsi_files end]]\""
				puts $fileId "/ {"
				puts $fileId "};"
				close $fileId
			} else {
				puts "Info: Board file: $board is not found and will not be added to the system-top.dts"
			}
		}
}

If there is a valid board found, then it will added to dtsi files. Then we can call this from our Makefile:

dts

build_dts:
	$(RM) -r my_dts
	$(TOOLS)/$(VERSION)/bin/xsct -eval "source xsct_script.tcl; build_dts -version $(VERSION) -board $(BOARD)"

Compile the devicetree (DTB)

dtb

build_dtb:
	$(RM) -r system.dtb
	export PATH=$$PATH:$(shell pwd)/dtc; \
	gcc -I my_dts -E -nostdinc -undef -D__DTS__ -x assembler-with-cpp -o my_dts/system-top.dts.tmp my_dts/system-top.dts; \
	dtc -I dts -O dtb -o system.dtb my_dts/system-top.dts.tmp

Note: Users can add the symbols by adding the -@ switch here. The symbols are added by default in petalinux

Create SD image

Create the BIF file with the contents below:

the_ROM_image:
{
	[fsbl_config] a53_x64
	[bootloader, destination_cpu=a53-0] zynqmp_fsbl/executable.elf
	[pmufw_image] zynqmp_pmufw/executable.elf
	[destination_device=pl] design_1_wrapper.bit
	[destination_cpu=a53-0, load=0x00100000] system.dtb
	[destination_cpu=a53-0,exception_level=el-3,trustzone] arm-trusted-firmware/build/zynqmp/release/bl31/bl31.elf
	[destination_cpu=a53-0,exception_level=el-2] u-boot-xlnx/u-boot.elf
}

Then in bootgen command from your Makefile

bootgen

bootimage:
	export PATH=$$PATH:$(shell pwd)/bootgen; \
	bootgen -arch zynqmp -image bootgen.bif -w -o BOOT.BIN

Downloading the RootFS:

There are released images for all Xilinx development boards. I will extract the rootfs from the image.ub here using dumpimage utility:

extract_rootfs

extract_rootfs:
	tar xvf $(VERSION)-$(BOARD)-release.tar.xz
	./u-boot-xlnx/tools/dumpimage -T flat_dt -p 2 $(VERSION)-$(BOARD)-release/image.ub -o petalinux-image-minimal-zynqmp-generic.cpio.gz

Creating the FIT image:

/dts-v1/;
/ {
          description = "U-Boot fitImage for plnx_aarch64 kernel";
          #address-cells = <1>;
          images {
                       kernel@0 {
                                   description = "Linux Kernel";
                                   data = /incbin/("./linux-xlnx/arch/arm64/boot/Image");
                                   type = "kernel";
                                   arch = "arm64";
                                   os = "linux";
                                   compression = "none";
                                   load = <0x80000>;
                                   entry = <0x80000>;
                                   hash@1 {
                                          algo = "sha1";
                                    };
                       };
                       fdt@0 {
                                  description = "Flattened Device Tree blob";
                                  data = /incbin/("./system.dtb");
                                  type = "flat_dt";
                                  arch = "arm64";
                                  compression = "none";
                                  hash@1 {
                                         algo = "sha1";
                                  };
                      };
                      ramdisk@0 {
                                   description = "ramdisk";
                                   data = /incbin/("./petalinux-user-image-plnx_aarch64.cpio.gz");
                                   type = "ramdisk";
                                   arch = "arm64";
                                   os = "linux";
                                   compression = "none";
                                   hash@1 {
                                          algo = "sha1";
                                   };
                      };
};
      configurations {
             default = "conf@1";
             conf@1 {
                          description = "Boot Linux kernel with FDT blob + ramdisk";
                          kernel = "kernel@0";
                          fdt = "fdt@0";
                          ramdisk = "ramdisk@0";
                          hash@1 {
                                algo = "sha1";
                          };
               };
               conf@2 {
                           description = "Boot Linux kernel with FDT blob";
                           kernel = "kernel@0";
                           fdt = "fdt@0";
                           hash@1 {
                                 algo = "sha1";
                           };
               };
       };
};

Use the command below to created the .ub file:

fit

fit_image:
	export PATH=$$PATH:$(shell pwd)/dtc; \
	./u-boot-xlnx/tools/mkimage -f fitimage.its image.ub

u-boot-xlnx/tools/mkimage -f fitimage.its image.ub

Load the BOOT.BIN and the image.ub and boot.scr on the SD card and boot.

Xilinx Wiki

ZCU102 Image creation in OSL flow

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