multiple device trees

multiple device trees

[Brad Bishop]

Does anyone have any experience supporting multiple system configurations in a monolithic flash image with multiple device trees?  Did you consider this and do something else instead?

thanks!

-brad

Re: multiple device trees

[Konstantin Klubnichkin]

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Re: multiple device trees

[Brad Bishop]

> On Jan 14, 2020, at 5:39 AM, Konstantin Klubnichkin <kitsok@yandex-team.ru> wrote:
> 
>  
> Hello, Brad!
>  
> I'm doing this using overlay DTS.
> I have a startup script that detects board type by GPIO pins and loads corresponding overlay.

Thanks for the reply Konstantin.  Does that mean you have the overlay patch applied to your kernel tree?

An alternative design that I am considering is having two complete device trees in a fit image, and u-boot reads the gpios to pick the correct dtb for linux.  Did you consider a design like that and if so, was there anything specific that sent you in the direction of overlays?

thx - brad

Re: multiple device trees

[Konstantin Klubnichkin]

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Re: multiple device trees

[Vijay Khemka]

On 1/14/20, 2:53 AM, "openbmc on behalf of Brad Bishop" <openbmc-bounces+vijaykhemka=fb.com@lists.ozlabs.org on behalf of bradleyb@fuzziesquirrel.com> wrote:

    
    
    > On Jan 14, 2020, at 5:39 AM, Konstantin Klubnichkin <kitsok@yandex-team.ru> wrote:
    > 
    >  
    > Hello, Brad!
    >  
    > I'm doing this using overlay DTS.
    > I have a startup script that detects board type by GPIO pins and loads corresponding overlay.
    
    Thanks for the reply Konstantin.  Does that mean you have the overlay patch applied to your kernel tree?
    
    An alternative design that I am considering is having two complete device trees in a fit image, and u-boot reads the gpios to pick the correct dtb for linux.  Did you consider a design like that and if so, was there anything specific that sent you in the direction of overlays?

This sounds like a great design, I was also thinking in this same direction. It will avoid kernel changes for overlays.
    
    thx - brad

Re: multiple device trees

[James Feist]

On 1/13/20 5:56 PM, Brad Bishop wrote:
> Does anyone have any experience supporting multiple system configurations in a monolithic flash image with multiple device trees?  Did you consider this and do something else instead?

We haven't thought about implementation yet, but someone on our team did 
some research into multiple dtb. In your conf file yocto lets you set 
multiple device trees:

KERNEL_DEVICETREE = "${KMACHINE}-one.dtb \
                      ${KMACHINE}-two.dtb"


Then you can pick which one to boot into in u-boot:

bootm 20080000#conf@two.dtb

At some point we were going to put some more research into this method, 
but we haven't yet.



> 
> thanks!
> 
> -brad
> 

Re: multiple device trees

[Alexander Amelkin]

Sorry for necroposting, but this is what we need now.

I did this previously with a non-OpenBMC system. What I did there was:

1. Make u-boot read an i2c-based FRU EEPROM, extract the 'Board Part 
Number' field and put it into a variable

2. Have the DTS files match the part numbers

3. Make u-boot `bootcmd` select the DTS based on the defined machine name

It would be nice to have such a feature built into OpenBMC for all 
platforms.

Alexander.

14.01.2020 04:56, Brad Bishop пишет:
> Does anyone have any experience supporting multiple system configurations in a monolithic flash image with multiple device trees?  Did you consider this and do something else instead?
>
> thanks!
>
> -brad