Hi Wolfgang,
On Monday 16 May 2011 12:25 AM, Wolfgang Denk wrote:
Dear Aneesh V,
In message1305202276-27784-6-git-send-email-aneesh@ti.com you wrote:
- Enable I-cache on bootup
- Enable MMU and D-cache immediately after relocation
- Do necessary initialization before enabling d-cache and MMU
Would it be possible to do this even _before_ relocation, so to speed up memory accesses during relocation? Of course, proper invalidates/ flushes will be needed before jumping to the RAM address, but I guess this would save a bit of boot times?
I intentionally kept it after relocation to avoid un-necessary complexities. Relocation is a case of self-modifying code. In Harvard architectures like armv7 there will be coherency issues unless we flush the entire D-cache(range based operation may be equally or more expensive) and invalidate the entire I-cache.
So, in effect everything has to be flushed to memory before you jump to the new location. There may be a small advantage because flushing from cache allows for bursting to the DDR where as bursting is not possible when d-cache is disabled. But I think this is not worth the trouble.
best regards, Aneesh