[U-Boot] Performance problems with gunzip

[Alessandro Rubini]

> I fear this is not as easy as flipping a bit in a register.  Depending
> on the platform caches tend to be tied to the MMU, so enabling the
> caches require setting up correct data structures for the MMU to work.
> That's the non-trivial work.

Not that difficult, either. You just need to fill the top-level
page table for 1MB sections (4096 sections = 16k bytes, which must
be aligned on a 16k boundary).

> Apart from that, there is CONFIG_CMD_CACHE which builds
> common/cmd_cache.c.  I see that at least two PXA250 platforms enable
> this, so maybe simply try that?

I think it's always disabled on arm, for the mmu reason.

> Maybe you can reap the code from their repository.  If you do, please
> post it here ;)

Or I can cook an RFC patch later, after redoing the 8815 patches.
I was just considering trying it these days, as I've done the same
on another straight-on-iron project and it's not that difficult.

/alessandro