[U-Boot] Modify go to allow chain loading a second u-boot

[U-Boot] Modify go to allow chain loading a second u-boot

[Helmut Raiger]

Hi,

   for all the wrong reasons I have to load a second u-boot from a first 
one.

I'm finally able to start it, but it only works if I do a 
cleanup_before_linux(),
i.e. turn off interrupts and caches before the actual 'go'.

For testing I patched the go command, but obviously this can't be
contributed as such.

Anyone having a suggestion on how to do this?

1) add option to 'go' command, which is hard as it has variable arguments
2) add another go command
3) use an environment variable to set the option for 'go'

Theoretically I could use an u-boot image to encapsulate the second u-boot
and use 'bootm', but I think I'll stumble over the same kind of questions.

Helmut
PS: this is a re-post (the original one hung on-to the thread where I 
asked for help in the first place).

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[U-Boot] Modify go to allow chain loading a second u-boot

[Simon Glass]

Hi,

On 3 April 2014 03:40, Helmut Raiger <helmut.raiger@hale.at> wrote:

> Hi,
>
>   for all the wrong reasons I have to load a second u-boot from a first
> one.
>
> I'm finally able to start it, but it only works if I do a
> cleanup_before_linux(),
> i.e. turn off interrupts and caches before the actual 'go'.
>
> For testing I patched the go command, but obviously this can't be
> contributed as such.
>
> Anyone having a suggestion on how to do this?
>
> 1) add option to 'go' command, which is hard as it has variable arguments
>

This seems best to me if you don't want to add a new command. Maybe you
could add a '-c' argument to cleanup?


> 2) add another go command
> 3) use an environment variable to set the option for 'go'


> Theoretically I could use an u-boot image to encapsulate the second u-boot
> and use 'bootm', but I think I'll stumble over the same kind of questions.
>
> Helmut
> PS: this is a re-post (the original one hung on-to the thread where I
> asked for help in the first place).
>
>
Regards,
Simon

[U-Boot] Modify go to allow chain loading a second u-boot

[Helmut Raiger]

On 04/08/2014 04:27 AM, Simon Glass wrote:
>
>     1) add option to 'go' command, which is hard as it has variable
>     arguments
>
>
> This seems best to me if you don't want to add a new command. Maybe 
> you could add a '-c' argument to cleanup?
>
This kind of option is clearly not what other u-boot commands use, I 
could not find a single command
that supports '-' style options. If this had been widely used, I 
wouldn't have asked in the first place.

Thanks anyway, answers are flowing in quite sparsely.

Helmut


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[U-Boot] Modify go to allow chain loading a second u-boot

[Wolfgang Denk]

Dear Helmut,

In message <53455133.5010200@hale.at> you wrote:
>
> > This seems best to me if you don't want to add a new command. Maybe 
> > you could add a '-c' argument to cleanup?
> >
> This kind of option is clearly not what other u-boot commands use, I 
> could not find a single command
> that supports '-' style options. If this had been widely used, I 
> wouldn't have asked in the first place.

It seems you did not look very carefully.  Just for example:

=> help env
env - environment handling commands

Usage:
env ask name [message] [size] - ask for environment variable
env default [-f] -a - [forcibly] reset default environment
env default [-f] var [...] - [forcibly] reset variable(s) to their default values
env delete [-f] var [...] - [forcibly] delete variable(s)
env edit name - edit environment variable
env export [-t | -b | -c] [-s size] addr [var ...] - export environment
env import [-d] [-t | -b | -c] addr [size] - import environment
env print [-a | name ...] - print environment
env run var [...] - run commands in an environment variable
env save - save environment
env set [-f] name [arg ...]


Best regards,

Wolfgang Denk

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DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
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diligence.                                           - Samuel Johnson

[U-Boot] Modify go to allow chain loading a second u-boot

[Helmut Raiger]

>> This kind of option is clearly not what other u-boot commands use, I
>> could not find a single command
>> that supports '-' style options. If this had been widely used, I
>> wouldn't have asked in the first place.
> It seems you did not look very carefully.  Just for example:
>
> => help env
> env - environment handling commands
>
Yes it seems ;-)

Thx, I'll look into that.
Helmut


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[U-Boot] Modify go to allow chain loading a second u-boot

[Rob Herring]

On Thu, Apr 3, 2014 at 4:40 AM, Helmut Raiger <helmut.raiger@hale.at> wrote:
> Hi,
>
>   for all the wrong reasons I have to load a second u-boot from a first one.

FYI, I can do this without problems on highbank. It's certainly useful
for development.

> I'm finally able to start it, but it only works if I do a
> cleanup_before_linux(),
> i.e. turn off interrupts and caches before the actual 'go'.

Most platforms (at least on ARM) don't enable interrupts, so your
problem is probably the cache. Loaded data (2nd u-boot) goes into the
d-cache and needs to be flushed to be in sync with the i-cache on
Harvard architecture processors. It works for me since the d-cache is
not enabled in u-boot on highbank (and all the init code is safe to
run twice).

> For testing I patched the go command, but obviously this can't be
> contributed as such.
>
> Anyone having a suggestion on how to do this?

The go command should have a defined state with respect to caches as
to how programs are entered. Loading code and jumping to it without
any cache maintenance is simply broken. Fix the go command. If an
architecture does not need a cache flush, then it should simply be a
nop.

Rob