Re: Using a custom device tree file

[Rainer Dorsch <ml@bokomoko.de>]

Hello,

Am Sonntag, 11. Februar 2018, 22:24:51 CET schrieb Rainer Dorsch:
> Am Sonntag, 11. Februar 2018, 13:20:07 CET schrieb Vagrant Cascadian:
> > On 2018-02-11, Rainer Dorsch wrote:
> > > I try to use a custom device tree file, but uEnv.txt does not have any
> > > effect:
> > > 
> > > rd@mohot:~$ cat /boot/uEnv.txt
> > > fdtfile=imx6dl-hummingboard-spi.dtb
> > 
> > ...
> > 
> > > Do I need to run flash-kernel or something else that uEnv.txt has any
> > > effect?
> > 
> > I don't believe the u-boot in Debian or mainline supports uEnv.txt for
> > the hummingboard variants. Or any of the variants supported in Debian's
> > u-boot package, though I haven't looked closely.
> > 
> > Try adding the following to /etc/flash-kernel/ubootenv.d/fdtfile:
> >   setenv fdtfile imx6dl-hummingboard-spi.dtb
> > 
> > And running flash-kernel to regenerate the boot script.
> 
> Thanks for your quick answer Vagrant.
> 
> In case I try to boot a broken dtb (kernel does not boot), is there a way
> back to the previous dtb?

AFAIK there are two ways to tell the kernel where to find the device tree:
-> append to the kernel binary
-> the bootloader handles this during boot and makes it available for the 
kernel

Can anybody tell, which method u-boot in Debian implements (in particular for 
the hummingboard)? 

Can anybody tell, if it is possible to configure from u-boot shell to loada 
custom device treefile?

Is that somewhere documented? The latest documentation on flash-kernelI found 
is from 2011... https://wiki.debian.org/FlashKernelRework

Thanks
Rainer

-- 
Rainer Dorsch
http://bokomoko.de/