[U-Boot] [PATCH] arm: Allow u-boot to run from offset base address

[Wolfgang Denk]

Dear Steve,

In message <53975EC2.1080209 at broadcom.com> you wrote:
> 
> > I still cannot understand why _start and CONFIG_SYS_TEXT_BASE would
> > have to be the same.  There is no such requirement.  What exactly
> > prevents you from assigning _start a location at offset 0x20 to the
> > start of the text segment, i. e. CONFIG_SYS_TEXT_BASE ?
> 
> Wolfgang et al.
> 
> I agree that they do not need to be the same...
> So our issue is that basically "for every ARMv7 board in the company", 
> we are currently maintaining our own modified/customized version of 
> "arch/arm/cpu/armv7/start.S" in order to add the appropriate 32 byte 
> header...

There should be more clever ways to implement this.  If nothing else
comes to mind, an #ifdef in "arch/arm/cpu/armv7/start.S" should be
sufficient to condistionally insert / adjust any offset that might be
needed for a specific board.

> And we could choose to do it using other methods, but they all require 
> us to maintain a customized version of linker scripts, or some other 
> code, or ....

... or a CONFIG setting in your board config file resp. your board's
defconfig.

> The request here is that with the addition of some relatively 
> straightforward (upstreamed) code, then this can be handled 
> automatically by a post-processing step and we would be able to use a 
> pristine version of the upstreamed code...

I'm sorry, but I disagree especially on the "straightforward" part.
Also, I see no reason to make the existing code unnecessarily complex,
and add more disadvantages (like increased meory footprint etc.) when
the same purpose can be implemented without adding any special code at
all.

> Our desire is to get this into the beginnings of the "ARMv8" boards, so 
> that we can avoid the maintenance issues we have with the current ARMv7 
> boards.
> 
> We appreciate your consideration of this request.

These are two different things: implementing a clean and easy way to
support a necessary feature is one thing; to do it in the suggested
way by adding code where none is needed is another thing.

I'm all for adding support for any features that are useful, even if
only for a single user, as long as they don't hurt other users.  All
I'm asking is to chose another way to implement this feature.  So far,
I did not see any arguments that my alternative proposals would cause
any problems to you?

Best regards,

Wolfgang Denk

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