[U-Boot] Skipping relocation RAM to RAM, esp. on i.MX6?

[Wolfgang Denk]

Dear Aneesh V,

In message <4F33614D.8020904 at ti.com> you wrote:
>
> > What exactly are you talking about here that "was adding a
> > considerable delay" - the memory copy ?  Are you really sure about
> > that?
> 
> I didn't measure it part by part, but removing relocation gave a
> noticeable speed-up, this platform is several orders of magnitude
> slower than the real silicon. So, that should not be surprising.

Could you please start using exact terminology, so we understand what
you actually refer to?  Did you really remove the _relocation_, i. e.
link for a static address, or did you just skip the memory copy?  Note
that the latter should be a no-op anyway if you just load the image to
the resulting target address.

> Maybe, I should stop the arguments now and wait till that framework is
> a reality.

I am very much convinced that you are tracking down a red herring.  It
does not really matter if you run the code on real silicon or in an
emulation - the relative times will always be the same.  Without any
detailed timing analysis I simply do not believe you that you really
have found a hot spot.  You focus on it because you found out that it
exists and you think it was "not needed" in your configuration -
without spending time on real optimization.

This is a fundamentally broken approach, and it will remain to be
broken even if new concepts get implemented that may make it easier to
skip certain steps of the initialization.

If you are concerned about boot time optimization, you _must_ start
with timing measurements.  You know where premature optimization leads
to, don't you?

Best regards,

Wolfgang Denk

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