[yocto] U-Boot with a different default device tree, for BeagleBone-similar system

[Matt Schuckmann]

> -----Original Message-----
> From: yocto-bounces at yoctoproject.org [mailto:yocto-
> bounces at yoctoproject.org] On Behalf Of Craig McQueen
> Sent: Monday, April 20, 2015 10:23 PM
> To: yocto at yoctoproject.org
> Subject: [yocto] U-Boot with a different default device tree, for
> BeagleBone-similar system
> 
> I'm working on a system based on the TI Sitara AM335x similar to the
> BeagleBone Black, but with various custom hardware. I've got a custom
> device tree for it, and it's working well.
> 
> In Yocto, I've defined a custom machine in a custom layer under
> conf/machine, derived from the BeagleBone Black machine with
> modifications. The kernel is compiling my device tree named something
> like am335x-myfantasticdevice.dtb, due to a KERNEL_DEVICETREE... line.
> However, U-Boot is still looking for the stock BeagleBone Black device
> tree named am335x-boneblack.dtb.
> 
> How can I modify my Yocto build so that U-Boot by default will expect a
> device tree with the name am335x-myfantasticdevice.dtb? I can see
> UBOOT_MACHINE but I'm not sure what I can do with it.
> 
> --

Hi Craig,

Your setup sounds just like mine. 
You need to modify u-boot itself to load your fdt file. The beaglebone black u-boot init routines reads some data from a eeprom at boot up to detect the board type and then configure things appropriately, including loading the appropriate fdt file.

In my layer I created a .bbappend file for u-boot to add board specific configuration header/source files with init routines for my board. In my case I just hardcoded the fdt file to load to my board file. 

I hope this helps. 

Matt S. 

> Craig McQueen
> 
> --
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