[U-Boot] [Question] How is the Falcon mode working

[Stefano Babic <sbabic@denx.de>]

Hi Frank,

On 07/04/2014 15:49, Frank Ihle wrote:
> Hi U-Boot,
> 
> you recently gave me the hint about the Falcon Mode for my Fast
> Booting investigations. But I think might got it wrong, could
> somebody correct me if so?:
> 
> - According to the "Falcon Mode" Pdf of October 2013
> (http://www.denx.de/wiki/pub/U-Boot/MiniSummitELCE2013/2013-ELCE-U-Boot-Falcon-Boot.pdf)
> The Falcon mode is just about to chose 2 different execution modes
> during startup - one that starts Linux directly (and skips u-boot)
> and the other for instance to make updates, or failsafe mode (and
> starts u-boot). Or does it even contain more functionality ?

The second starts U-Boot as you are used to.

> - According to the "Minimizing boot times using U-Boot Falcon Mode"
> Pdf of July 2012 
> (http://schedule2012.rmll.info/IMG/pdf/LSM2012_UbootFalconMode_Babic.pdf)
> it's mentioned that this can only run with boards, which are able to
> work with SPL. I guess here SPL means Second Programm Bootloader. I'm
> not an expert in this area, but wouldn't it be possible to run every
> board with an SPL, since it's just Software like a Bootloader?

Of course, but not all boards supported in mainline were converted to
use SPL, and for this reason not all boards support out of the box
Falcon Mode.

> And if
> not what is the "real" eye of the needle here ? I'm just asking
> because I didn't get the problem here.

It is simply a snapshot of the current U-Boot mainline. The switch
between Linux/U-Boot is implemented in SPL, and this makes sense because
SPL is much smaller that the whole U-Boot, dropping also the time that a
SOC needs to load an image from the storage media.

Best regards,
Stefano Babic

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