[coreboot] unrv2b delay (v2)
stepan at coresystems.de
Wed Oct 29 21:41:36 CET 2008
Marc Jones wrote:
> Arne Georg Gleditsch wrote:
>> Peter Stuge <peter at stuge.se> writes:
>>> Arne Georg Gleditsch wrote:
>>>> The unrv2b uncompression algorithm appears to behave very badly in
>>>> the absence of a proper cache.
>>> But why does this improve when the algorithm runs out of RAM?
>>> Could ROM accesses be a factor?
>> Yes, at least in the sense that running from ROM means we're running
>> from an uncached memory region. I assume you'd notice much the same
>> running from uncached DRAM as well. copy_and_run is one of the few
>> things that run after cache-as-ram has been disabled but before our code
>> has been copied to proper DRAM, so it is especially sensitive regarding
>> code footprint.
> I have thought about this a while back and have wanted to make a
> change. Disabling CAR should fixup the stack etc but for performance
> reasons we should setup/leave ROM and RAM caching enabled on the BSP.
> If you are interested in looking at that I think it would be great.
What CPU/chipset is this? On quite some ROM stays cacheable all the
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