[U-Boot] AM335x: enabling datacache in SPL slows down system?

[Wolfgang Denk]

Dear "Bas van den Berg",

In message <20130620080523.aba38cb4 at mail.altenpts.nl> you wrote:
> 
> I'm trying to optimize the boottime for an AM335x based board. Currently
> we're loading the kernel from SPL directly (falcon mode). Loading the kernel
> from flash to ram takes roughly 3 seconds.
> When doing this from U-boot itself with 'nand read .., it only takes 1.8 seconds.
> It seems that U-boot has data_cache enabled, while SPL did not.
> 
> When enabling the data cache with dcache_enable(), loading takes 3.5 seconds,
> so even slower! The enabling itself does not take a significant amount of time.

We observed the very same issue with the verry first prototype
implementation of Falcon mode on an AM3517 based board.  At this time
we did not have time nor resources to figure out what exactly was
causing this issue, but it's interesting to see that 1) it
still persists and 2) it also happens on AM335x

> Anyone have any idea why enabling the data cache slows SPL down?
> Or does U-boot do anything else that I'm missing?

@Tom: do you have any additional input what we should check?

Best regards,

Wolfgang Denk

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