View source for Yocto Customizing U-Boot AM62

<!-- Set release according to "release" parameter in URL and use am62-yocto-dunfell-5.10.168_08.06.00.42-v1.0 as default
--> {{INIT_RELEASE_PARAM|am62-yocto-kirkstone-6.1.46_09.01.00.08-v1.0}}<!--
--> {{#lst:Yocto_Platform_Customization|{{#var:RELEASE_PARAM}}}} <!--
--> {{#vardefine:WORKDIR|~/{{#var:MACHINE_NAME}}-u-boot}} <!--
--> {{#vardefine:WORKDIR_ENV|$WORKDIR}} <!--
--> {{PageHeader|Yocto Build U-Boot from source code}} {{DocImage|category1=Yocto|category2={{#var:HARDWARE_NAME}}}} __toc__

= Introduction =

This guide demonstrates how to patch and rebuild the VAR-SOM-AM62 U-Boot images using Yocto.

To learn how to build the U-Boot images outside of Yocto, see: {{Varlink|Yocto_Build_U-Boot_TI|{{#var:RELEASE_LINK}}|'''Build U-Boot from source code'''}}

= Before Starting =

Before starting this guide, you must have the Yocto environment setup and be able to build images for the VAR-SOM-AM62.

Please see: {{Varlink|Yocto_Build_Release|{{#var:RELEASE_LINK}}|'''Build Yocto from source code'''}}.

The remainder of the guide assumes the Yocto working directory is '''~/var-ti-yocto'''

= Patching Yocto =

Fetch the U-Boot source: 
{{GIT_FETCH|NAME=U-BOOT|WORKDIR={{#var:WORKDIR_ENV}}}}

Checkout the version of U-Boot that is aligned with '''SRCREV''' in '''~/var-ti-yocto/tisdk/sources/meta-variscite-bsp-ti/recipes-bsp/u-boot/u-boot-variscite_<u-boot version>.bb'''

For example, if:

 SRCREV = "fbbe3117f5daa78d6df922b4f2d33154de1495b1"

Then run:

 $ cd ti-u-boot
 $ git checkout fbbe3117f5daa78d6df922b4f2d33154de1495b1

Next, make the desired changes to the U-Boot source code. After changing the source code, create a diff file:

 $ git diff > ~/var-ti-yocto/tisdk/sources/meta-variscite-bsp-ti/recipes-bsp/u-boot/u-boot-variscite/uboot.diff

Finally, configure '''~/var-ti-yocto/tisdk/sources/meta-variscite-bsp-ti/recipes-bsp/u-boot/u-boot-variscite_<u-boot version>.bb''' to apply the patch by appending:

 SRC_URI += "file://uboot.diff"

= Building U-Boot using Yocto =

Build the U-Boot images by running:

 $ cd ~/var-ti-yocto/tisdk/build
 $ . conf/setenv
 
 # Build only the U-Boot images:
 $ MACHINE=am62x-var-som bitbake -c deploy u-boot-variscite                    # tispl.bin and u-boot.img
 $ MACHINE=am62x-var-som bitbake -c deploy mc:k3r5:u-boot-variscite            # tiboot3.bin
 
 # Optionally, you may skip building U-Boot and just build your image:
 $ MACHINE=am62x-var-som bitbake <image name>

The relevant output files are:

 deploy-ti/images/am62x-var-som/u-boot.img
 deploy-ti/images/am62x-var-som/tispl.bin
 deploy-ti/images/am62x-var-som/tiboot3.bin

see: {{Varlink|Yocto_Build_U-Boot_TI|{{#var:RELEASE_LINK}}#Update_U-Boot_on_running_system|'''Build U-Boot from source code'''}} to learn how to update a running board with these images.