Hello!
I am working with a VAR-SOM-AM43 dev board from a company called Variscite. The company doesn't support u-boot builds for this board after the migration to Kconfig (maintenance happens on a 2014.07 branch), and I would like to port the board to more recent u-boot sources.
The SoC on the dev board is a Texas Instruments AM4738 ARM processor. My understanding of the abstraction layers is - Architecture: ARM - CPU: armv7 - SoC: AM33xx - Board: varsomam43 - target build configurations
The vendor supplied Yocto layer includes the board support source files (board.*, mux.c, etc), so my plan had been to build u-boot with the board (and config, based on the old boards.cfg entry) being varsomam43: - CONFIG_VARSOMAM43 (board) - CONFIG_TARGET_VARSOMAM43 (target)
Once I had these legacy configurations working with the new source tree I was planning to migrate the code to the Kconfig way of doing things (which I'm still learning about).
That is my plan, but there are a few things that are unclear to me or that I am unsure of. - Is my plan a sensible approach? - Do I understand the board/config layer division correctly? It is not clear to me that I shouldn't build my board with the AM43XX board definition (that is what the Variscite sources are based on anyway), with the dev board I am using defined as a target of that board. Should it be Soc:AM33XX, Board:AM43XX, Target:varsomam43; or SoC:AM33XX, Board:varsomam43, Target:varsomam43, or some combination thereof? - Why do the AM43XX evm boards use the AM33XX SoC definition, even though they are a part of the AM43XX soc series (on chip peripherals), and the external differences (external peripherals, pin mux configurations) are configured in the evm definitions? - In the current ti-u-boot source tree in am43xx_evm_defconfig CONFIG_AM43XX=y is defined, but not CONFIG_TARGET_AM43XX_EVM, and the Kconfig options in the board source file are conditional upon that symbol ("if TARGET_AM43XX_EVM"). How are the Kconfig defaults configured, and am43xx_evm.h selected for the AM43XX_EVM target? - I have watched Marek Vasut's (thanks Marek!) ELC presentation on board porting, and been reading README.kconfig, but I still feel like I am feeling my way forward by trial and error. Are there any other documents or sources that I should be reading?
All tips, pointers, and help warmly received!
Thanks, Tim