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From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
To: benh@kernel.crashing.org
Cc: scottwood@freescale.com, chris.pringle@oxtel.com,
	linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
	arnd@arndb.de
Subject: Re: PowerPC PCI DMA issues (prefetch/coherency?)
Date: Wed, 17 Jun 2009 09:37:14 +0900	[thread overview]
Message-ID: <20090617093654B.fujita.tomonori@lab.ntt.co.jp> (raw)
In-Reply-To: <1245197925.21602.0.camel@pasglop>

On Wed, 17 Jun 2009 10:18:45 +1000
Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:

> On Tue, 2009-06-16 at 20:02 +0200, Arnd Bergmann wrote:
> > On Tuesday 16 June 2009, Scott Wood wrote:
> > > > If the
> > > > device is the only one, you can also use dma_alloc_noncoherent() and
> > > > flush explicitly with dma_cache_sync().
> > > 
> > > I don't see how that would help -- aren't those also controlled by 
> > > CONFIG_NOT_COHERENT_CACHE?
> > 
> > Ah, yes you are right. PowerPC implements dma_alloc_noncoherent as
> > dma_alloc_coherent, so dma_cache_sync() is actually a NOP (or should be).
> 
> But we still need to sync the result of dma_map_* when used multiple
> times for a single mapping.

We have dma_sync_{single|sg}_for_{cpu|device} API for the above
purpose.

dma_cache_sync is supposed to be used only with the buffers that
dma_alloc_noncoherent() returns. On architecutures that maps
dma_alloc_noncoherent to dma_alloc_coherent, dma_cache_sync() is
supposed to be NOP.

  reply	other threads:[~2009-06-17  0:50 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <4A37A503.3030209@oxtel.com>
     [not found] ` <20090616162114.GA5051@loki.buserror.net>
     [not found]   ` <4A37C97A.5050508@oxtel.com>
2009-06-16 16:46     ` PowerPC PCI DMA issues (prefetch/coherency?) Scott Wood
2009-06-16 16:57       ` Chris Pringle
2009-06-16 17:03         ` Scott Wood
2009-06-16 17:43           ` Arnd Bergmann
2009-06-16 17:49             ` Scott Wood
2009-06-16 18:02               ` Arnd Bergmann
2009-06-17  0:18                 ` Benjamin Herrenschmidt
2009-06-17  0:37                   ` FUJITA Tomonori [this message]
2009-06-17  0:56                     ` Leon Woestenberg
2009-06-17  1:08                       ` Benjamin Herrenschmidt
2009-06-17  1:13                         ` Leon Woestenberg
2009-06-17  1:07                     ` Benjamin Herrenschmidt
2009-06-17  7:58           ` Chris Pringle
2009-06-17 13:18             ` Chris Pringle
2009-06-18 11:24               ` Chris Pringle
2009-06-22 14:31                 ` AW: " Sergej.Stepanov
2009-06-29  8:11                   ` Chris Pringle
2009-06-16 14:08 Chris Pringle
2009-06-16 15:48 ` Roderick Colenbrander

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