device tree on rpi2 not working

Phil Elwell phil at
Wed Dec 16 01:34:38 PST 2015

That documentation is correct - the correct DTB is loaded automatically
by the firmware provided it finds the RPTL trailer saying that the
kernel is DT-capable; passing a DT-blob to a kernel that is expecting
ATAGs is a good way to stop it booting, but unzipping a compressed
kernel to check its capabilities is an expensive operation, which is why
the trailer and the mkknlimg tool were created.

By adding an explicit device_tree value you have overridden the trailer
detection, forcing the firmware into DT mode, which is fine provided you
don't want to share your SD card between different models of Pi.

On 15/12/2015 22:51, Tim Sander wrote:
>> My guess would be that you didn't specify the .dtb file in the
>> > firmware's config.txt. The firmware is what loads and delivers it to the
>> > kernel, and does some edits in the process.  The config.txt line would
>> > look something like:
>> > 
>> > device_tree=bcm2709-rpi-2-b.dtb
>> > (possibly under dtbs/kernelversion/, depending on how you installed)
> Dammit, hit the nail on the head. But to my defense i have to say that the 
> documentation on this:
> let me belive that its loaded automatically and i don't have to specifiy it 
> explicitly. Anyhow i am really happy to get an solution :-).

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