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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 operating system 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>path/to/yocto/poky
source oe-init-build-env
cd ..

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:

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   cd <path_to_yocto>path/to/yocto/poky git clone -b dunfell https://github.com/kraj/meta-altera.git

   
   

2. Add meta-altera to yocto project with:

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

   
   

Create custom meta 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:

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   bitbake-layers create-layer .path/to/yocto/poky/meta-custom

   
   

2. The created layer contains a sample recipes folder, that can be removed:

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   rm -rf .path/to/yocto/poky/meta-custom/recipes-example

   
   

3. Make meta-custom dependent on meta-altera:

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   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:

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

   
   

Add required parameters to local.conf

1. First the variable "MACHINE" must be redefined in the local.conf file. Several machines are defined in the meta-altera layer (see meta-altera/conf/machine for more information). In this example, the machine 'cyclone5' is used.
   Remove the default value and add 'cyclone5':

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   sed -i '/^MACHINE/s/MACHINE/#MACHINE/g' path/to/yocto/poky/build/conf/local.conf echo -e '\nMACHINE = "cyclone5"' >> path/to/yocto/poky/build/conf/local.conf

   
   

2. For the linux kernel in the meta-altera layer it's required to define a the preferred provider and version in local.conf (see meta-altera/recipes-kernel/linux for other linux kernel versions):

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   echo -e '\nPREFERRED_PROVIDER_virtual/kernel = "linux-altera-lts"' >> path/to/yocto/poky/build/conf/local.conf echo -e 'PREFERRED_VERSION_linux-altera-lts = "5.4%"' >> path/to/yocto/poky/build/conf/local.conf

   
   

3. Set the preferred u-boot version for meta-altera in local.conf (see meta-altera/recipes-bsp/u-boot for other u-boot versions):

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

Create workspace

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 of u-boot , do the following steps:

1. It is not possible to call menuconfig if UBOOT_CONFIG is defined. But UBOOT_CONFIG is needed to assign a defconfig file to UBOOT_MACHINE. UBOOT_MACHINE must therefore be defined manually. The variable UBOOT_CONFIG is predefined in the machine configuration file for cyclone5 with the value 'cyclone5-socdk' (see meta-altera/conf/machine/cyclone5.conf). The associated defconfig file is therefore socfpga_cylcone5_defconfig (see meta-altera/recipes-bsp/u-boot/u-boot-socfpga-common.inc). Accordingly these variables must be defined in local.conf:

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   echo -e '\nUBOOT_MACHINE = "socfpga_cyclone5_defconfig"' >> path/to/yocto/poky/build/conf/local.conf echo -e 'UBOOT_CONFIG = ""' >> path/to/yocto/poky/build/conf/local.conf

   
   

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

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   devtool modify u-boot-socfpga -O

   Make

   
   

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:

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   devtool menuconfig u-boot-socfpga

   
   

2. Exit and save your configuration. devtool-fragment.cfg will be created automatically.Make changes to the

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:

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   cd path/to/yocto/poky/build/workspace/sources/u-boot-socfpga

   
   

2. Run a build to test your changes:

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   devtool build u-boot-socfpga

   
   

3. Add the changes made with:

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   git add .

   
   

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

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   git commit -m "<message>"

   
   

5. If you want to generate more patches, repeat

   step a

   steps 1 -

   d

   4, otherwise navigate back to the poky directory:

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   cd

   <path_to_yocto>

   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

Finish u-boot modification

Remove the UBOOT_CONFIG and UBOOT_MACHINE variables from local.conf if you use the default defconfig file for the MACHINE 'cyclone5':

sed -i '/UBOOT_MACHINE = "socfpga_cyclone5_defconfig"/d' path/to/yocto/poky/build/conf/local.conf
sed -i '/UBOOT_CONFIG = ""/d' path/to/yocto/poky/build/conf/local.conf

Configure linux kernel

Prepare linux kernel configuration in workspace

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

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

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   devtool modify linux-altera-lts -O

   Launch menuconfig with following command and make your changes, exit and save your configuration:

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   devtool menuconfig linux-altera-lts

   Make changes to the linux-altera-lts configuration

   
   

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:

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   devtool menuconfig linux-altera-lts

   
   

2. Exit and save your configuration. devtool-fragment.cfg will be created automatically.Make changes to

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:

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   cd path/to/yocto/poky/build/workspace/sources/linux-altera-lts

   
   

2. Run a build to test your changes:

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   devtool build linux-altera-lts

   
   

3. Add the changes made with:

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   git add .

   
   

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

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   git commit -m "<message>"

   
   

5. If you want to generate more patches, repeat step

   a

   1 -

   d

   4, otherwise navigate back to the poky directory:

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   cd

   <path_to_yocto>

   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 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

required files to custom 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):

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   ~/intelFPGA_lite/20.1/embedded/embedded_command_shell.sh

   
   

3. navigate to your quartus project directory and convert the handoff data into source code:

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   cd path/to/quartus/project mkdir -p build bsp-create-settings --type spl --bsp-dir build \ --preloader-settings-dir hps_isw_handoff/soc_system_hps_0/ \ --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:

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   wget https://github.com/altera-opensource/u-boot-socfpga/blob/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:

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   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:

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   cd path/to/yocto/poky recipetool edit u-boot-socfpga

   
   

   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):

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   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.

References

1. Linux Kernel Development Manual
2. Reference Manual#devtool Quick Reference
3. u-boot-socfpga/doc/README.socfpga
4. Patching _ the _ source _ for _ a _ recipe