Re: [ECOS] ppc603e cache sync

[Jesper Skov <jskov@cygnus.co.uk>]

>>>>> "Daniel" == Daniel Kahlin <tlr@netinsight.se> writes:

>> The only other place were we do this by steam is in the kcache
>> tests. There the array is called 'dca' - data cache array or some
>> such. Not something that has been blessed with official policy
>> (yet).

Daniel> I will have to put and ifdef:ed array somewhere in the hal.
Daniel> maybe in arch/hal_misc.c.  cyg_uint8
Daniel> hal_data_cache_array[HAL_DCACHE_SIZE]

Looks good to me. Remember to use GCC attributes to ensure proper
alignment.

>> Doesn't it have the implementation specific flush-all command as
>> the 603? I don't have my manuals close by, unfortunately, but the
>> 603 definitely has a one-shot operation for flushing (or is it
>> clearing?)  the cache.

Daniel> You probably mean the DCFI bit in HID0.  It invalidates the
Daniel> cache, and that would be fine, if it wasn't for the cache
Daniel> being writeback.  But maybe I've missed something in the
Daniel> documentation.

Yup, that's what I was thinking about. If there's only the DCFI bit,
that's probably all. Too bad.

>> If not, maybe something like the below would be better (from my
>> Linux/APUS sources):

Daniel> The problem with using the 'dcbz' (and all other) cache
Daniel> instructions is that the operate on memory addresses instead
Daniel> of indexes into the cache.  Normally that is what you want,
Daniel> but if you want to flush all cache entries into memory you
Daniel> would have to scan the entire 32 bit address range.  Trick:
Daniel> Allocate all entries of the cache to an unused area.

You are right. I've been bitten by that before - but I do think we
found some way around it. I forget.

Your solution is fine if it works.

Jesper