[U-Boot] Switch from mmcboot to ramboot?

[Lukasz Majewski <l.majewski@majess.pl>]

Hi Grant,

> > > How can I tell u-boot to boot with the ramboot= definition
> > > instead of mmcboot= ?
> > >
> > > - Grant
> >
> > You need to change environmental variable bootcmd
> >
> > setenv bootcmd ramboot
> > saveenv
> > run bootcmd
> >
> > or simpler:
> >
> > Stop u-boot -> and access prompt
> >
> > then,
> >
> > run ramboot
> 
> Hi Lucasz, that didn't work for me and I think it's because of the
> variables set by 'make am335x_evm_defconfig'.  It seems like there
> are a set of standard u-boot commands and a higher level of variables
> set by 'make am335x_evm_defconfig' which appear in
> include/configs/am335x_evm.h and prevent you from using the standard
> u-boot commands in uEnv.txt.
I can give you an example with Samsung's soc.

When you execute 'make trats_defconfig' then default envs defined at
include/trats.h are compiled in.

Then if envs are broken (or not available), then those values are
default.

Please type ? at u-boot prompt and look for env commands.
When you type the command, then context help appears.

On Samsung's SoCs you can easily write those default envs to memory
(oneNAND or eMMC) with 'envs default'. And then edit those stored
values (as I've written previously).


> 
> For example, even after adding the following to the top of my
> uEnv.txt:

I'm not familiar with am335x_evm board and I don't know what is the
purpose of uEnv.txt.

I may just guess, that this is a default command list to execute.

Please investigate the "env" command if it can work for you.

> 
> setenv bootcmd ramboot
> saveenv
> 
> I still get:
> 
> "Booting from mmc ..."
> 
> I'm struggling to figure out how to use the framework provided by
> 'make am335x_evm_defconfig' in uEnv.txt.  Can you point me to info on
> how to do that?
> 
> - Grant

Regards,
Lukasz