[U-Boot] "armv7: integrate cache maintenance support" breaks km_kirkwood ethernet

[Wolfgang Denk]

Dear Aneesh V,

In message <4E32C223.2050309 at ti.com> you wrote:
> 
> I had written a small write-up on this earlier today in the below
> thread:
> http://marc.info/?l=u-boot&m=131193466800729&w=2

Thanks.

> I had done extensive testing on the armv7 cache-maintenance APIs by
> creating coherency issues and solving them using the APIs. I believe
> the problems are due to the APIs not being appropriately used where
> they need to be used, also coupled with the fact that dcache_enable()
> is now called from board_init_r().

Yes, this is the problem - now suddenly a large number of drivers
which are not prepared to run with caches on break.

> Maybe, I should also write a README with guidelines for correct cache
> usage.

That would be nice, too. TIA!

> Also, I would suggest the following to solve the problem with breaking
> boards:
> 1. Allow boards to define CONFIG_SYS_DCACHE_OFF and/or
> 2. Instead of calling dcache_enable() from board_init_r() let's call a
> new function like dcache_init(). The default implementation of this
> function shall do nothing. The real implementation in platform code may
> enable or disable d_cache() on a per SoC/board basis.

I think approach 2. is the better one (we should try to avoid
unnecessary #ifdef's).  But instead of doing nothing, the default
implementation should print a warning "dcache: not enabled", so users
and board maintainers are permanently aware which boards have not been
adapted / fixed yet :-)

Thanks!

Best regards,

Wolfgang Denk

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