From: Arnd Bergmann <arnd@arndb.de>
To: linuxppc-dev@lists.ozlabs.org
Subject: Re: PowerPC PCI DMA issues (prefetch/coherency?)
Date: Tue, 16 Jun 2009 19:43:38 +0200
User-Agent: KMail/1.11.90 (Linux/2.6.30-8-generic; KDE/4.2.85; x86_64; ; )
Cc: Scott Wood <scottwood@freescale.com>,
       Chris Pringle <chris.pringle@oxtel.com>, linux-kernel@vger.kernel.org
References: <4A37A503.3030209@oxtel.com> <4A37CF02.5080906@oxtel.com> <4A37D073.6020802@freescale.com>
In-Reply-To: <4A37D073.6020802@freescale.com>
MIME-Version: 1.0
Content-Type: Text/Plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Message-Id: <200906161943.38764.arnd@arndb.de>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 793
Lines: 19

On Tuesday 16 June 2009, Scott Wood wrote:
> Chris Pringle wrote:
> > Ah right - that would explain what we're seeing then... Doh. Thought I 
> > might have been onto something then. Is there any way to force a cache 
> > flush? That'd at least prove it was a caching issue if it resolved the 
> > problem.
> 
> You could enable CONFIG_NOT_COHERENT_CACHE.

If the whole system is noncoherent, that is the right solution. If the
device is the only one, you can also use dma_alloc_noncoherent() and
flush explicitly with dma_cache_sync().

	Arnd <><
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/