[Buildroot] [At91Bootstrap3] Overriding dtb chosen arguments for kernel command line

[Buildroot] [At91Bootstrap3] Overriding dtb chosen arguments for kernel command line

[Alejandro Ariel Fachini]

Hello:
I have been using at91bootstrap3 to directly load kernel, using dtb on
sam9x35ek, this kernel is mounting UBI RFS file.
Wel i need to mount another file JFFS2 and i want to change parameters in
Kernel Command Line.
I treid from inside at91bootstrap3-v3.8.6 terminal using make menuconfig
and selecting override kernel comand line but got error.
Also tried manually changing arguments in linux menu config and still get
the arguments inside DTB.
How can i do this? Thank you very much.
Note: I am not using U-Boot, using U-Boot is working ok.
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[Buildroot] [At91Bootstrap3] Overriding dtb chosen arguments for kernel command line

[Thomas Petazzoni]

Hello,

On Fri, 23 Mar 2018 16:15:32 -0300, Alejandro Ariel Fachini wrote:

> I have been using at91bootstrap3 to directly load kernel, using dtb on
> sam9x35ek, this kernel is mounting UBI RFS file.
> Wel i need to mount another file JFFS2 and i want to change parameters in
> Kernel Command Line.
> I treid from inside at91bootstrap3-v3.8.6 terminal using make menuconfig
> and selecting override kernel comand line but got error.
> Also tried manually changing arguments in linux menu config and still get
> the arguments inside DTB.
> How can i do this? Thank you very much.
> Note: I am not using U-Boot, using U-Boot is working ok.

Do you have CONFIG_ARM_ATAG_DTB_COMPAT enabled in your kernel
configuration ?

I suppose when you boot with U-Boot, U-Boot patches the DTB before
passing it to the kernel.

However, I don't think at91bootstrap3 patches the DTB, it probably just
passes an old style ATAGS, which the kernel will only pick up if
CONFIG_ARM_ATAG_DTB_COMPAT=y.

Note: this is just an hypothesis, I haven't actually checked the
at91bootstrap3 code.

Best regards,

Thomas Petazzoni
-- 
Thomas Petazzoni, CTO, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com