From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Matthew Wilcox <matthew@wil.cx>
Cc: linux-mips@linux-mips.org, linux-ia64@vger.kernel.org,
linux-sh@vger.kernel.org, linux-mm@kvack.org,
sparclinux@vger.kernel.org,
Marek Szyprowski <m.szyprowski@samsung.com>,
linux-arch@vger.kernel.org,
Stephen Rothwell <sfr@canb.auug.org.au>,
Jonathan Corbet <corbet@lwn.net>,
x86@kernel.org, Arnd Bergmann <arnd@arndb.de>,
microblaze-uclinux@itee.uq.edu.au,
linaro-mm-sig@lists.linaro.org,
Andrzej Pietrasiewicz <andrzej.p@samsung.com>,
Thomas Gleixner <tglx@linutronix.de>,
linux-arm-kernel@lists.infradead.org, discuss@x86-64.org,
linux-kernel@vger.kernel.org,
Kyungmin Park <kyungmin.park@samsung.com>,
linux-alpha@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 00/14] DMA-mapping framework redesign preparation
Date: Sat, 24 Dec 2011 18:00:14 +1100 [thread overview]
Message-ID: <1324710014.6632.23.camel@pasglop> (raw)
In-Reply-To: <20111223163516.GO20129@parisc-linux.org>
On Fri, 2011-12-23 at 09:35 -0700, Matthew Wilcox wrote:
> I really think this wants to be a separate function.
> dma_alloc_coherent
> is for allocating memory to be shared between the kernel and a driver;
> we already have dma_map_sg for mapping userspace I/O as an alternative
> interface. This feels like it's something different again rather than
> an option to dma_alloc_coherent.
Depends. There can be some interesting issues with some of the ARM stuff
out there (and to a lesser extent older ppc embedded stuff).
For example, some devices really want a physically contiguous chunk, and
are not cache coherent. In that case, you can't keep the linear mapping
around. But you also don't waste your precious kernel virtual space
creating a separate non-cachable mapping for those.
In general, dma mapping attributes as a generic feature make sense,
whether this specific attribute does or not though. And we probably want
space for platform specific attributes, for example, FSL embedded
iommu's have "interesting" features for directing data toward a specific
core cache etc... that we might want to expose using such attributes.
Cheers,
Ben.
next prev parent reply other threads:[~2011-12-24 7:01 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-23 12:27 [PATCH 00/14] DMA-mapping framework redesign preparation Marek Szyprowski
2011-12-23 12:27 ` [PATCH 01/14] common: dma-mapping: introduce alloc_attrs and free_attrs methods Marek Szyprowski
2012-01-16 1:57 ` David Gibson
2011-12-23 12:27 ` [PATCH 02/14] X86: adapt for dma_map_ops changes Marek Szyprowski
2011-12-23 12:27 ` [PATCH 03/14] MIPS: " Marek Szyprowski
2012-02-13 10:35 ` [PATCH 03/14 v2] " Marek Szyprowski
2012-02-13 10:41 ` Sergei Shtylyov
2012-02-13 12:41 ` [PATCH 03/14 v3] " Marek Szyprowski
2011-12-23 12:27 ` [PATCH 04/14] PowerPC: " Marek Szyprowski
2012-01-16 8:09 ` David Gibson
2012-02-13 10:36 ` [PATCH 04/14 v2] " Marek Szyprowski
2011-12-23 12:27 ` [PATCH 05/14] IA64: " Marek Szyprowski
2012-03-27 21:20 ` Tony Luck
2012-03-27 21:53 ` Luck, Tony
2011-12-23 12:27 ` [PATCH 06/14] SPARC: " Marek Szyprowski
2011-12-23 12:27 ` [PATCH 07/14] Alpha: " Marek Szyprowski
2011-12-23 12:27 ` [PATCH 08/14] SH: " Marek Szyprowski
2011-12-23 12:27 ` [PATCH 09/14] Microblaze: " Marek Szyprowski
2011-12-23 12:27 ` [PATCH 10/14] Unicore32: " Marek Szyprowski
2011-12-23 12:27 ` [PATCH 11/14] common: dma-mapping: remove old alloc_coherent and free_coherent methods Marek Szyprowski
2011-12-23 12:27 ` [PATCH 12/14] common: dma-mapping: introduce mmap method Marek Szyprowski
2011-12-23 12:27 ` [PATCH 13/14] common: DMA-mapping: add WRITE_COMBINE attribute Marek Szyprowski
2011-12-23 12:27 ` [PATCH 14/14] common: DMA-mapping: add NON-CONSISTENT attribute Marek Szyprowski
2011-12-23 16:35 ` [PATCH 00/14] DMA-mapping framework redesign preparation Matthew Wilcox
2011-12-24 7:00 ` Benjamin Herrenschmidt [this message]
2011-12-27 8:25 ` Marek Szyprowski
2011-12-27 17:53 ` James Bottomley
2011-12-28 12:52 ` Marek Szyprowski
2012-01-10 8:42 ` Marek Szyprowski
2012-02-13 10:40 ` [PATCH] Hexagon: adapt for dma_map_ops changes Marek Szyprowski
2012-02-24 15:48 ` [PATCH 00/14] DMA-mapping framework redesign preparation Arnd Bergmann
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