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→Device tree handling
{{Applies To BoraX}}
{{InfoBoxBottom}}
__FORCETOC__
== History ==
|September 2018
|First public release
|-
|1.1.0
|November 2018
|Added missing command to generate the DTB file
|-
|}
== Introduction ==
As explained [[Logical_structure_of_Bora_and_BoraX_Embedded_Linux_Kits_(BELK/BXELK)|here]], BELK/BXELK structure is not based on the [https://www.xilinx.com/products/design-tools/embedded-software/petalinux-sdk.html PetaLinux build system](*). Instead, BELK/BXELK make use of a standardized Yocto-based build system to build all the software components—U-Boot, Linux kernel, and root filesystem—that run on the Processing System (PS). This choice approach is more flexible and more modularized but it requires a little bit more knowledge of embedded Linux systems.
That being said, there are cases in which it can be convenient to build such components with PetaLinux build system, however. This technical note shows how to use the PetaLinux build system to build the Linux kernel image released with BELK/BXELK with PetaLinux build system.
The procedure was tested with the following configuration.
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It is assumed that PetaLinux is already properly installed on the host machine (for more details, please refer to [https://www.xilinx.com/support/documentation-navigation/see-all-versions.html?xlnxproducttypes=Design%20Tools&xlnxdocumentid=UG1144 ''UG1144 - PetaLinux Tools Documentation: Reference Guide'']). (*)Please note that PetaLinux itself works on top of the Yocto build system.
== Building the Linux kernel Kernel ==
First of all, set up the PetaLinux environment:
<pre class="workstation-terminal">
dvdk@osboxes:~/devel/bora/prj/bora_1/components$mkdir ext_sources
dvdk@osboxes:~/devel/bora/prj/bora_1/components$cd ext_sources
dvdk@osboxes:~/devel/bora/prj/bora_1/components/ext_sources$git clone http://git@git.dave.eu/bora/linux-xlnx.git -b bora-4.x.x
Cloning into 'linux-xlnx'...
...
Open the PetaLinux configuration menu and set up the kernel source
<pre class="workstation-terminal">
dvdk@osboxes:~/devel/bora/prj/bora_1$ petalinux-config
</pre>
Configure the build system in order to use a custom directory for device tree include files: enable the ''Auto Config Settings --> Specify a manual device tree include directory'' item and set the ''Manual device tree include directory'' to <code>${TOPDIR}/../components/ext_sources/linux-xlnx/arch/arm/boot/dts/include</code>:
[[File:Belk petalinux kernel4.png|thumb|center|600px]]
Set the ''Root file system type'' to ''NFS'' in order to generate a <code>uImage</code> that doesn't include any file system:
[[File:Belk petalinux kernel5.png|thumb|center|600px]]
[INFO] sourcing bitbake
INFO: bitbake virtual/kernel
Loading cache: 100% |######################################################################################################################| Time: 0:00:00Loaded 3234 entries from dependency cache.Parsing recipes: 100% |####################################################################################################################| Time: 0:0200:1403Parsing of 2446 .bb files complete (0 2410 cached, 2446 36 parsed). 3236 targets, 224 skipped, 0 masked, 0 errors.
NOTE: Resolving any missing task queue dependencies
Initialising tasks: 100% |#################################################################################################################| Time: 0:00:2257Checking sstate mirror object availability: 100% |#########################################################################################| Time: 0:00:1321
NOTE: Executing SetScene Tasks
NOTE: Executing RunQueue Tasks
linux-xlnx-4.9-belk-4.0.0+git999-r0 do_compile: NOTE: linux-xlnx: compiling from external source tree /home/dvdk/devel/bora/prj/bora1bora_1/build/../components/ext_sources/linux-xlnxfsbl-2017.2+gitAUTOINC+122565ec40-r0 do_compile: NOTE: fsbl: compiling from external source tree /opt/petalinux/tools/hsm/data/embeddedswNOTE: Tasks Summary: Attempted 2410 tasks of which 2349 1869 didn't need to be rerun and all succeeded.
INFO: Copying Images from deploy to images
INFO: Creating images/linux directory
You can also run generated qemu images with a command like 'runqemu qemux86'
INFO: Adding user layer: /home/dvdk/devel/bora/prj/bora1bora_1/project-spec/meta-user
INFO: generating uImage
INFO: bitbake -R /home/dvdk/devel/bora/prj/bora1bora_1/build/conf/kerneltype.conf virtual/kernel Parsing recipes: 100% |####################################################################################################################| Time: 0:0103:5609
Parsing of 2446 .bb files complete (0 cached, 2446 parsed). 3236 targets, 224 skipped, 0 masked, 0 errors.
NOTE: Resolving any missing task queue dependencies
Initialising tasks: 100% |#################################################################################################################| Time: 0:00:1617
Checking sstate mirror object availability: 100% |#########################################################################################| Time: 0:00:12
NOTE: Executing SetScene Tasks
NOTE: Executing RunQueue Tasks
linux-xlnx-4.9-belk-4.0.0+git999-r0 do_compile: NOTE: linux-xlnx: compiling from external source tree /home/dvdk/devel/bora/prj/bora1bora_1/build/../components/ext_sources/linux-xlnxNOTE: Tasks Summary: Attempted 2410 tasks of which 2374 2349 didn't need to be rerun and all succeeded.</pre> Compile the device tree:<pre class="workstation-terminal">dvdk@osboxes:~/devel/bora/prj/bora_1$ petalinux-build -v -c device-tree[INFO] building device-tree[INFO] sourcing bitbakeINFO: bitbake virtual/dtbLoading cache: 100% |###################################################################################################################################| Time: 0:00:00Loaded 3233 entries from dependency cache.Parsing recipes: 100% |#################################################################################################################################| Time: 0:01:45Parsing of 2446 .bb files complete (2413 cached, 33 parsed). 3236 targets, 224 skipped, 0 masked, 0 errors.NOTE: Resolving any missing task queue dependenciesInitialising tasks: 100% |##############################################################################################################################| Time: 0:00:02Checking sstate mirror object availability: 100% |######################################################################################################| Time: 0:00:02NOTE: Executing SetScene TasksNOTE: Executing RunQueue TasksNOTE: Tasks Summary: Attempted 748 tasks of which 748 didn't need to be rerun and all succeeded.INFO: Copying Images from deploy to images[INFO] successfully built device-tree
</pre>
After the build is completed, the <code>uImage</code> file and the device tree blob (<code>system.dtb</code>) are located in the <code>images/linux</code> directory.
===Device tree handling===
One of the most appreciated features of PetaLinux is the automatic generation of the Linux Device Tree including the nodes associated with the IPs instantiated in the PL. When used in combination with the Device Tree provided by the BELK/BXELK, this generation process works as depicted in the following image.
[[File:BELK-PetaLinux-DTB.png|thumb|center|600px|Combined Device Tree generation process]]
In essence, PetaLinux combines the original Bora/BoraX device tree (<code>bora.dts</code>) with another auxiliary device tree generated on the base of hardware description file (.hdf). The resulting DTB (<code>system.dtb</code>) provides all the nodes required by the system to operate properly.
It is worth remembering that the user can add further customizations to the resulting DTB by editing this file <code><plnx-projroot>/project-spec/meta-user/recipes-bsp/device-tree/files/system-user.dtsi</code>. For more details, please refer to the ''Xilinx UG1144 PetaLinux Tools Documentation - Reference Guide''.
