[U-Boot] Falcon mode with initrd

[Stefano Babic]

Hi Tim,

On 27/05/2015 17:22, Tim Harvey wrote:
> Stefano,
> 
> You may perhaps be the most knowledgeable about Falcon mode based on
> the presentations I've found on the web.
> 
> It seems to me that there is currently no support in U-Boot for using
> Falcon mode where the kernel is separate from the initrd.

If you mind if SPL in Falcon mode loads both kernel and initrd, you're
right. This is not supported. SPL loads only one image.

> I see that
> the 'spl' command is passed the initrd_addr so that it can setup
> atags/fdt (I haven't followed through the code to understand what it
> does with this addr yet) but there is no support in any of the
> common/spl/spl_*.c files for loading anything other than args or
> kernel.

Yes, the command are thought to prepare the setup for the kernel, ATAGS
or DT, but not to load something else.

> 
> Have you had any thoughts on this?

The way to load more as one image in U-Boot should be via the FIT image.
You can have separate kernel and initrd, and by using the mkimage you
can combine them. SPL will still load one single image (I guess some
changes are required to allow Falcon to load a FIT), but it is much more
general and let open to have a Falcon Boot combined with Secure Boot.

> It seems to me a new #define would
> need to be created per storage medium pointing to the offset/sector of
> initrd and used at compile time. Perhaps your thoughts have always
> been that if you want to use an initrd for falcon mode you must always
> build it into the kernel?

Really in most projects I do not use initrd at all and the rootfs is
mounted on a storage (NOR/NAND/..), without a initrd as distros are used
to do. When a initrd is required, my preferences go to build a FIT image
combinining zImage (not anymore uImage), initrd and DT.

Best regards,
Stefano

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