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

[Simon Glass]

Hi,

On Thu, Sep 15, 2011 at 10:41 AM, Mike Frysinger <vapier at gentoo.org> wrote:
> 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
>

Right, I am going to resubmit this patch in the
arch/arm/cpu/armv7/tegra2 directory and see how that looks.

Regards,
Simon