From: "Gerhard Pircher" <gerhard_pircher@gmx•net>
To: Eugene Surovegin <ebs@ebshome•net>
Cc: linuxppc-dev@ozlabs•org, debian-powerpc@lists•debian.org
Subject: Re: Not coherent cache DMA for G3/G4 CPUs: clarification needed
Date: Thu, 20 Apr 2006 23:10:55 +0200 (MEST) [thread overview]
Message-ID: <10026.1145567455@www088.gmx.net> (raw)
In-Reply-To: 20060420210201.GA25755@gate.ebshome.net
> --- Ursprüngliche Nachricht ---
> Von: Eugene Surovegin <ebs@ebshome•net>
> An: Gerhard Pircher <gerhard_pircher@gmx•net>
> Kopie: linuxppc-dev@ozlabs•org, debian-powerpc@lists•debian.org
> Betreff: Re: Not coherent cache DMA for G3/G4 CPUs: clarification needed
> Datum: Thu, 20 Apr 2006 14:02:01 -0700
>
> On Thu, Apr 20, 2006 at 10:56:33PM +0200, Gerhard Pircher wrote:
> > > --- Urspr?ngliche Nachricht ---
> > > Von: Eugene Surovegin <ebs@ebshome•net>
> > > An: Gerhard Pircher <gerhard_pircher@gmx•net>
> > > Kopie: linuxppc-dev@ozlabs•org, debian-powerpc@lists•debian.org
> > > Betreff: Re: Not coherent cache DMA for G3/G4 CPUs: clarification
> > > needed
> > > Datum: Thu, 20 Apr 2006 13:38:48 -0700
> > >
> > > There are already non-coherent cache PPC archs (8xx, 4xx) just look
> > > how all this implemented there, don't reinvent the wheel.
> > >
> > > Also, read Documentation/DMA-API.txt and DMA-mapping.txt
> > I know! Unfortunately this implementation does not work at all with
> > G3/G4 PPC desktop CPUs for various reasons (for example due to the BAT
> > mapping, page tables with different access attributes for the same
> > physical memory area allocated by the consistent DMA functions, etc.).
>
> We have the same situation on 44x (all kernel memory is mapped
> through several big TLBs and consistent functions allocate additional
> cache-inhibited mappings for the same physical pages).
Well, Freescale's PPC programming environment manual clearly states that
this will not work on G4 CPUs (74xx). Also Benjamin Herrenschmidt told me,
that this implementation will not work for the reasons I mentioned before.
The approach I'm trying to implement was his idea, so I have to trust in
him.
regards,
Gerhard
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next prev parent reply other threads:[~2006-04-20 21:10 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-04-20 18:57 Not coherent cache DMA for G3/G4 CPUs: clarification needed Gerhard Pircher
2006-04-20 20:38 ` Eugene Surovegin
2006-04-20 20:56 ` Gerhard Pircher
2006-04-20 21:02 ` Eugene Surovegin
2006-04-20 21:10 ` Gerhard Pircher [this message]
2006-04-20 21:55 ` Eugene Surovegin
2006-04-20 22:08 ` Gerhard Pircher
2006-04-24 19:21 ` Mark A. Greer
2006-04-21 4:38 ` Benjamin Herrenschmidt
2006-04-21 8:03 ` Gerhard Pircher
2006-04-21 14:33 ` Brent Cook
2006-04-21 21:51 ` Benjamin Herrenschmidt
2006-04-27 21:31 ` Mark A. Greer
2006-04-27 21:53 ` Benjamin Herrenschmidt
2006-04-27 22:08 ` Mark A. Greer
2006-04-29 17:57 ` Gerhard Pircher
2006-04-20 21:06 ` Benjamin Herrenschmidt
2006-04-20 21:13 ` Eugene Surovegin
2006-04-20 21:19 ` Eugene Surovegin
2006-04-20 22:40 ` Benjamin Herrenschmidt
2006-04-20 22:39 ` Benjamin Herrenschmidt
2006-04-20 23:46 ` Gabriel Paubert
2006-04-21 0:09 ` Benjamin Herrenschmidt
2006-04-20 21:33 ` Eugene Surovegin
2006-04-20 22:41 ` Benjamin Herrenschmidt
2006-04-21 8:21 ` Gerhard Pircher
2006-04-20 21:03 ` Benjamin Herrenschmidt
2006-04-20 21:33 ` Gerhard Pircher
2006-04-20 22:07 ` Gabriel Paubert
2006-04-20 22:26 ` Gerhard Pircher
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