Not coherent cache DMA for G3/G4 CPUs: clarification needed

Gerhard Pircher gerhard_pircher at gmx.net
Fri Apr 21 08:08:18 EST 2006


> --- Ursprüngliche Nachricht ---
> Von: Eugene Surovegin <ebs at ebshome.net>
> An: Gerhard Pircher <gerhard_pircher at gmx.net>
> Kopie: linuxppc-dev at ozlabs.org, debian-powerpc at lists.debian.org
> Betreff: Re: Not coherent cache DMA for G3/G4 CPUs: clarification needed
> Datum: Thu, 20 Apr 2006 14:55:14 -0700
> 
> Well, you aren't the first person who tries to run G4 with 
> CONFIG_NOT_COHERENT_CACHE. This was done before and I don't remember 
> that those people had to implement anything as complex as you are 
> trying to do.

Maybe these systems have cache coherent northbridges, which is not the case
for the AmigaOne and its "famous" ArticiaS northbridge.

> You can try asking on #mklinux. It always better to ask people who 
> actually _did_ this :).
> 
> In fact, I just grepped 2.6 and found 
> #ifdef(CONFIG_NOT_COHERENT_CACHE) in syslib/mv64x60.c. Guess what 
> systems usually have this type of bridge? Not 4xx/8xx, that's for sure.

Hmm, strange. AFAIK the NOT_COHERENT_CACHE config option is available only
for the 4xx and 8xx platforms. Wouldn't the config option depend on
CONFIG_6XX too, if there are not cache coherent systems with G4 cpus? 

At least I could not compile in the dma-mapping.c file without modifying the
Kconfig file.

> Good luck.

Thanks!

Gerhard

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