[U-Boot] U-Boot NOR Flash Copy Time Reduction

[Wolfgang Denk]

Dear yyurtcan,

In message <1463133956025-254877.post at n7.nabble.com> you wrote:
> We have P4080DS board and u-boot for bootloader. We want to reduce to time to
> copy kernel image from NOR Flash to RAM.  Can we optimize p4080ds u-boot NOR
> Flash copy time? If so, How?

If you think about it, then you will realize that the copy time
depends on the bandwidth for the copy operation and the amount of data
being copied.  So you want to do two things:

- maximize copy bandwidth:

  o Make sure your CPU and your memory busses are configured for
    maximum clock speed
  o Make sure both your RAM and your NOR flash (I assume you are
    talking about parallel NOR flash here) get initialized with
    optimal (fasted still stable) parameters
  o Make sure instruction and data caches are enabled

- minimize image size:

  o Remove everything from your kernel configuration what is not
    really essentially needed for your system
  o Compile any drivers that are not needed for initial startup as
    modules and only load these when convenient
  o Chose optimal compression method for the kernel image [*]

That's it.  Actually quite simple...

[*] You may notice that you will get different results what the
    "optimal compression method" is when you consider only the "image
    load time" (as was your question here) versus "total boot time",
    which will also include the time needed to uncompress the image.

Best regards,

Wolfgang Denk

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