[U-Boot] [PATCH] tegra2: Enable data cache

[Mike Frysinger]

On Thursday, September 15, 2011 13:30:09 Albert ARIBAUD wrote:
> I agree on the need and interest to support cache. I disagree on the way
> to get there. Turning cache off indiscriminately and hoping that board
> developers/maintainer turn their caches off will only lead to U-Boot
> failing in interesting ways and cluttering the mailing list with
> requests for help until someone figures out the cache is the culprit.

if code only works when cache is turned on, that usually means the code is 
broken and is missing appropriate barriers/flushes.  turning cache on doesnt 
fix the underlying issue, it ignores it.  ive seen this in the past with 
Blackfin parts where our testers will do some operation with caches on, and 
then try things with caches off, and trigger bugs in drivers due to missing 
syncs but things work due to implicit timings with cache on.

> We have started outlining a solution (weak generic cache (non-)functions
> in arch/arm/lib/cache.c which only warn about cache not being enabled,
> and cpu/SoC/board specific versions that enable cache where it works.

which is causing the copy & paste i'm whining about

> We also have started discussing minimizing cache code copy -- admittedly
> spinned off a patch submission discussion, so it may have been missed,
> and I will repost the RFC in its own thread -- whereby the cache
> functions  would be defined as weak function in the lib, and could be
> overriden by ISA-level function, which themselves could be overriden by
> CPU-level functions, and SoC (or even board) level functions could
> override them all.

i guess i did miss it.  it doesnt matter to me how we get to the ultimate 
destination ({I,D}CACHE_ON/etc...), just that ultimately the crappy/dead SoC's 
are not bogging down the modern/maintained ones by forcing the common 
implementation to suck.
-mike
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