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It is possible to customize existing meta layers by creating an own meta layer with bitbake append files. In this description the meta layer meta-altera for Intel FPGA devices is used as reference.

For more informations about the OS used and the sources and versions of yocto project or meta-altera layer, see Yocto KICKstart#Used source files.

Initialize the environment


Before starting to create a custom meta layer, navigate to the yocto poky directory and initialize the environment with the following commands:

cd path/to/yocto/poky
source oe-init-build-env

Download required sources


Since the created meta-custom layer should depend on meta-altera, these sources files must be downloaded and added to the yocto project.

  1. Navigate to yocto poky directory and download meta-altera layer:

    cd path/to/yocto/poky
    git clone -b dunfell https://github.com/kraj/meta-altera.git
  2. Add meta-altera to yocto project with:

    cd path/to/yocto/poky/build
    bitbake-layers add-layer ./meta-altera

Create BSP layer


In this example, the created layer is named meta-custom. If you want to use a different name, just replace "custom".

  1. Create own layer "meta-custom" with:

    bitbake-layers create-layer path/to/yocto/poky/meta-custom
  2. The created layer contains a sample recipes folder, that can be removed:

    rm -rf path/to/yocto/poky/meta-custom/recipes-example
  3. Make meta-custom dependent on meta-altera:

    sed -i '/LAYERDEPENDS_meta-custom/s/core/meta-altera/g' path/to/yocto/poky/meta-custom/conf/layer.conf 
  4. Add the meta-custom layer to the yocto project with:

    bitbake-layers add-layer path/to/yocto/poky/meta-custom

Configure BSP Machine


In the machine configuration file, you can store general settings for the custom BSP layer, such as the version of u-boot or the linux kernel. Here, we will use the cyclone5 machine configuration file from the meta-altera layer as a template. For other machine configurations in the meta-altera layer, see meta-altera/conf/machine.

  1. Download the cyclone5 machine configuration file to the meta-custom layer and rename it:

    mkdir -p path/to/yocto/poky/meta-custom/conf/machine
    cd path/to/yocto/poky/meta-custom/conf/machine
    wget https://github.com/kraj/meta-altera/raw/dunfell/conf/machine/cyclone5.conf
    mv cyclone5.conf custom.conf
  2. Make the following changes to the content of custom.conf:
    1. Change the name in line 2 from 'cyclone5' to 'custom' and customize the variables UBOOT_EXTLINUX_DEFAULT_LABEL and UBOOT_EXTLINUX_MENU_DESCRIPTION_default:

      sed -i '/^#@NAME:/s/.*/#@NAME: custom/g' path/to/yocto/poky/meta-custom/conf/machine/custom.conf
      sed -i '/^UBOOT_EXTLINUX_DEFAULT_LABEL/s/".*"/"Cyclone5 custom SDMMC"/g' path/to/yocto/poky/meta-custom/conf/machine/custom.conf
      sed -i '/^UBOOT_EXTLINUX_MENU_DESCRIPTION_default/s/".*"/"Cyclone5 custom SDMMC"/g' path/to/yocto/poky/meta-custom/conf/machine/custom.conf
    2. The KMACHINE variable defines the MACHINE name, which is referenced in the build/conf/local.conf file. Redefine KMACHINE with your own MACHINE name:

      sed -i '/^KMACHINE/s/".*"/"custom"/g' path/to/yocto/poky/meta-custom/conf/machine/custom.conf
    3. For the linux kernel in the meta-altera layer it's required to define a the preferred provider and version in custom.conf (see Yocto KICKstart#Used source files for more information about the version used). Add the provider and version for linux kernel:

      echo -e '\nPREFERRED_PROVIDER_virtual/kernel = "linux-altera-lts"' >> path/to/yocto/poky/meta-custom/conf/machine/custom.conf 
      echo -e 'PREFERRED_VERSION_linux-altera-lts = "5.4%"' >> path/to/yocto/poky/meta-custom/conf/machine/custom.conf
    4. Set the preferred u-boot version for meta-altera in custom.conf (see Yocto KICKstart#Used source files for more information about the version used):

      echo -e '\nPREFERRED_VERSION_u-boot-socfpga = "v2021.04%"' >> path/to/yocto/poky/meta-custom/conf/machine/custom.conf

Other variables in the custom.conf file are changed or added at other points in this guide.

Add required parameters to local.conf


Before you start configuring the meta-custom layer, the MACHINE variable in the path/to/yocto/poky/build/conf/local.conf file must be set to the correct machine. The correct machine name is defined in the meta-custom/conf/machine/custom.conf file with the variable KMACHINE.
Remove the default value of the MACHINE variable in local.conf and add the new MACHINE 'custom':

sed -i '/^MACHINE/s/MACHINE/#MACHINE/g' path/to/yocto/poky/build/conf/local.conf
echo -e '\nMACHINE = "custom"' >> path/to/yocto/poky/build/conf/local.conf

Create workspace


The following command creates the workspace directory and adds it to bblayers.conf:

devtool create-workspace

Configure u-boot


Prepare u-boot configuration in workspace

To prepare the u-boot sources for modify the default configuration and create patches, do the following steps:

  1. To set the correct default defconfig file for the u-boot, it is required to set the UBOOT_MACHINE variable in the meta-custom/conf/machine/custom.conf file. The defconfig file 'socfpga_cylcone5_defconfig' will be used as default u-boot configuration (see meta-altera/recipes-bsp/u-boot/u-boot-socfpga-common.inc for other Intel fpga defconfig files). If UBOOT_MACHINE has been defined, UBOOT_CONFIG is no longer needded.
    Remove the variable UBOOT_CONFIG and add UBOOT_MACHINE to meta-custom/conf/machine/custom.conf:

    sed -i '/^UBOOT_CONFIG/d' path/to/yocto/poky/meta-custom/conf/machine/custom.conf
    echo -e '\nUBOOT_MACHINE = "socfpga_cyclone5_defconfig"' >> path/to/yocto/poky/meta-custom/conf/machine/custom.conf
    
  2. Run following command to prepare the workspace and fetch and unpack the sources:

    devtool modify u-boot-socfpga -O

Configure u-boot with menuconfig

To make changes to u-boot configuration, follow these steps:

  1. Launch menuconfig with following command and make your changes:

    devtool menuconfig u-boot-socfpga
  2. Exit and save your configuration. devtool-fragment.cfg will be created automatically.

Create patches for u-boot source files

Do following steps to create patches for u-boot source files:

  1. Navigate to u-boot-socfpga in the workspace and add, modify or remove files:

    cd path/to/yocto/poky/build/workspace/sources/u-boot-socfpga
  2. Run a build to test your changes:

    devtool build u-boot-socfpga
  3. Add the changes made with:

    git add .
  4. Commit your changes and add a short message. The message is used to name the patch file:

    git commit -m "<message>"

    If you get the following error message: "*** Please tell me who you are. Run ...", run this commands to define a name and email:

    git config --local user.email "oe.patch@oe"
    git config --local user.name "OpenEmbedded"
  5. If you want to generate more patches, repeat steps 1 - 4, otherwise navigate back to the poky directory:

    cd path/to/yocto/poky

Create and update u-boot recipe bbappend

Add the devtool-fragment.cfg and the patches to the meta-custom layer with:

devtool update-recipe u-boot-socfpga -a path/to/yocto/poky/meta-custom -O

Configure linux kernel


Prepare linux kernel configuration in workspace

To prepare the linux kernel sources for modify the default configuration and create patches, do the following steps:

  1. Run following command to prepare the workspace and fetch and unpack the sources:

    devtool modify linux-altera-lts -O

Configure linux kernel with menuconfig

To make changes to linux kernel configuration, follow these steps:

  1. Launch menuconfig with following command and make your changes:

    devtool menuconfig linux-altera-lts
  2. Exit and save your configuration. devtool-fragment.cfg will be created automatically.

Create patches for linux kernel source files

Do following steps to create patches for u-boot source files:

  1. Navigate to linux-altera-lts in the workspace and add, modify or remove files:

    cd path/to/yocto/poky/build/workspace/sources/linux-altera-lts
  2. Run a build to test your changes:

    devtool build linux-altera-lts
  3. Add the changes made with:

    git add .
  4. Commit your changes and add a short message. The message is used to name the patch file:

    git commit -m "<message>"
  5. If you want to generate more patches, repeat step 1 - 4, otherwise navigate back to the poky directory:

    cd path/to/yocto/poky

Create and update linux kernel recipe bbappend

Add the devtool-fragment.cfg and the patches to the meta-custom layer with:

devtool update-recipe linux-altera-lts -a path/to/yocto/poky/meta-custom -O

Remove workspace


Remove the workspace from bblayers.conf and delete the workspace folder:

cd path/to/yocto/poky/build
bitbake-layers remove-layer workspace
rm -rf path/to/yocto/poky/build/workspace

Add custom files to meta layer


Add handoff files to u-boot

If you create a u-boot file for an Intel Cyclone V / Arria V with quartus version 20.1 you have to convert the handoff data into source code.

  1. compile your quartus project
  2. run the embedded command shell (Intel SoC EDS):

    ~/intelFPGA_lite/20.1/embedded/embedded_command_shell.sh
  3. navigate to your quartus project directory and convert the handoff data into source code:

    cd path/to/quartus/project
    mkdir -p build
    bsp-create-settings --type spl --bsp-dir build \
    --preloader-settings-dir hps_isw_handoff/* \
    --settings build/settings.bsp

Next you have to run the qts_filter to take the sources from the handoff folder, format them and copy them to u-boot source code.

  1. Fetch qts_filter.sh from github:

    wget https://raw.githubusercontent.com/altera-opensource/u-boot-socfpga/socfpga_v2021.04/arch/arm/mach-socfpga/qts-filter.sh
  2. Run qts_filter for cyclone5 to format and copy the handoff files to custom meta layer:

    mkdir -p path/to/yocto/poky/meta-custom/recipes-bsp/u-boot/u-boot-socfpga/qts
    ./qts-filter.sh cyclone5 \
    				path/to/quartus/project \
    				path/to/quartus/project/build \
    				path/to/yocto/poky/meta-custom/recipes-bsp/u-boot/u-boot-socfpga/qts
  3. Add the generated files to the u-boot bbappend file:

    cd  path/to/yocto/poky/meta-custom/recipes-bsp/u-boot
    gedit u-boot-socfpga*.bbappend

    Add qts_filter files and the following task to copy the qts_filter files to the correct place in u-boot sources during build image (if your are using another board, you have to adjust the file path):

    SRC_URI += "file://qts/iocsr_config.h \
    			file://qts/pinmux_config.h \
    			file://qts/pll_config.h \
    			file://qts/sdram_config.h \
    			"
    
    do_configure_prepend () {
    	install -m 0644 ${WORKDIR}/qts/iocsr_config.h ${S}/board/altera/cyclone5-socdk/qts
    	install -m 0644 ${WORKDIR}/qts/pinmux_config.h ${S}/board/altera/cyclone5-socdk/qts
    	install -m 0644 ${WORKDIR}/qts/pll_config.h ${S}/board/altera/cyclone5-socdk/qts
    	install -m 0644 ${WORKDIR}/qts/sdram_config.h ${S}/board/altera/cyclone5-socdk/qts
    }

For more information see u-boot-socfpga/doc/README.socfpga.

Add custom device tree

u-boot

To add an own device tree to u-boot do following steps:

  1. Copy the .dts/.dtsi files to meta-custom/recipes-bsp/u-boot/u-boot-socfpga/dts:

    mkdir -p path/to/yocto/poky/meta-custom/recipes-bsp/u-boot/u-boot-socfpga/dts
    cp custom.dts path/to/yocto/poky/meta-custom/recipes-bsp/u-boot/u-boot-socfpga/dts/custom.dts
    cp custom-u-boot.dtsi path/to/yocto/poky/meta-custom/recipes-bsp/u-boot/u-boot-socfpga/dts/custom-u-boot.dtsi
  2. Add the .dts/.dtsi files to the u-boot bbappend file:

    cd  path/to/yocto/poky/meta-custom/recipes-bsp/u-boot
    gedit u-boot-socfpga*.bbappend

    Copy the following code to the u-boot bbappend file to copy the files to the correct directory and add them to the correct Makefile:

    SRC_URI += "[...]
    			file://dts/custom.dts \
    			file://dts/custom-u-boot.dtsi \
    			"
    
    do_configure_prepend () {
    	[...]
    	install -m 0644 ${WORKDIR}/dts/custom.dts ${S}/arch/arm/dts
    	install -m 0644 ${WORKDIR}/dts/custom-u-boot.dtsi ${S}/arch/arm/dts
    }
  3. Redefine the variable UBOOT_EXTLINUX_FDT_default with the file name of your device tree in the machine configration file of meta-custom:

    sed -i '/^UBOOT_EXTLINUX_FDT_default/s/".*"/"..\/custom.dtb"/g' path/to/yocto/poky/meta-custom/conf/machine/custom.conf
  4. Change in menuconfig the device tree to custom.dts:
    1. Run menuconfig as described here: Configure u-boot (Note: If a devtool-fragment.cfg file for u-boot already exists in the meta-custom layer, you should update it manually, otherwise the existing changes there will be deleted)
    2. Go to Boot options → Default fdt file and change the value to 'custom.dtb'
    3. Go to Device Tree Control → Default Device Tree for DT control and change the value to 'custom'

linux kernel

Adding your own device tree to the linux kernel is similar to the steps above:

  1. Copy the .dts file to meta-custom/recipes-kernel/linux/linux-altera-lts/dts:

    mkdir -p path/to/yocto/poky/meta-custom/recipes-kernel/linux/linux-altera-lts/dts
    cp custom.dts path/to/yocto/poky/meta-custom/recipes-kernel/linux/linux-altera-lts/dts/custom.dts
  2. Add the .dts file to the linux kernel bbappend file:

    cd  path/to/yocto/poky/meta-custom/recipes-kernel/linux
    gedit liunx-altera-lts*.bbappend

    Copy the following code to the linux kernel bbappend file to copy the files to the correct directory during image generation:

    SRC_URI += "[...]
    			file://dts/custom.dts \
    			"
    
    do_configure_prepend () {
    	[...]
    	install -m 0644 ${WORKDIR}/dts/custom.dts ${S}/arch/${ARCH}/boot/dts
    }
  3. Redefine the variable KERNEL_DEVICETREE with the file name of your device tree in the machine configration file of meta-custom.

    1. Open the custom.conf file:

       gedit path/to/yocto/poky/meta-custom/conf/machine/custom.conf
    2. Delete the content of the variable KERNEL_DEVICETREE and add your customized device tree:

      KERNEL_DEVICETREE = "custom.dtb"
      

(optional) Add fpga configuration file to meta layer

It is possible to add an fpga configuration file to the meta layer, which is used to configure the fpga from u-boot.

  1. First generate an rbf file from the sof file generated by the quartus project:
    1. run the nios ii command shell (Intel Quartus):

      ~/intelFPGA_lite/20.1/nios2eds/nios2_command_shell.sh
    2. run following command to convert the sof file to rbf:

      cd path/to/quartus/project/output_files
      quartus_cpf -c -o bitstream_compression=on custom.sof soc_system.rbf
  2. Run following commands to create a recipe in the specified directory:

    mkdir -p path/to/yocto/poky/meta-custom/recipes-bsp/rbf
    cat > path/to/yocto/poky/meta-custom/recipes-bsp/rbf/custom-rbf.bb << EOF
    DESCRIPTION = "Add fpga configuration file to image"
    LICENSE = "MIT"
    LIC_FILES_CHKSUM = "file://\${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302" 
    
    PACKAGE_ARCH = "\${MACHINE_ARCH}"
    PV = "1.0\${PR}" 
    
    FILESEXTRAPATHS_prepend := "\${THISDIR}/files:"
    SRC_URI = " file://soc_system.rbf"  
    
    do_install () {
    	install -d \${D}/images/\${MACHINE}
    	install -m 0644 \${WORKDIR}/test_board.rbf \${D}/images/\${MACHINE}
    	install -d \${DEPLOY_DIR}/images/\${MACHINE}
    	cp \${WORKDIR}/test_board.rbf \${DEPLOY_DIR}/images/\${MACHINE}
    }
    
    FILES_\${PN} += "/images/\${MACHINE}" 
    
    EOF
  3. Create the files folder in meta-custom/recipes-bsp/rbf and copy the rbf file there:

    mkdir -p path/to/yocto/poky/meta-custom/recipes-bsp/rbf/files
    cp path/to/soc_system.rbf path/to/yocto/poky/meta-custom/recipes-bsp/rbf/files/
  4. Add with the variable IMAGE_BOOT_FILES the rbf file to the FAT partition of the image in the machine configuration file of meta-custom layer:

    echo -e '\nIMAGE_BOOT_FILES += "soc_system.rbf"' >> path/to/yocto/poky/meta-custom/conf/machine/custom.conf
  5. Modify the image recipe to add the createed recipe to your image. This command refers to the provided image core-image-minimal.bb, you can also create your own image recipe and add your created recipes.

    echo -e '\nIMAGE_INSTALL_append = " custom-rbf"' >> path/to/yocto/poky/meta/recipes-core/images/core-image-minimal.bb
  6. Add the following commands to CONFIG_BOOTCOMMAND via u-boot menuconfig, so that u-boot will configure the fpga with the rbf file:

    1. Run menuconfig as described here: Configure u-boot (Note: If a devtool-fragment.cfg file for u-boot already exists in the meta-custom layer, you should update it manually, otherwise the existing changes there will be deleted)
    2. Go to Boot options and enable 'Enable a default value for bootcmd'
    3. Change the value of 'bootcmd value' to 'load mmc 0:1 $loadaddr soc_system.rbf; fpga load 0 $loadaddr $filesize; bridge enable; run distro_bootcmd'

References


  1. Linux Kernel Development Manual
  2. Reference Manual#devtool Quick Reference
  3. Board Support Package (BSP) Developers's Guide
  4. u-boot-socfpga/doc/README.socfpga
  5. Patching the source for a recipe
  6. Intel SoC EDS User Guide


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