From: Christoph Lameter <cl@linux.com>
To: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>,
linux-arm-kernel@lists.infradead.org,
"'Daniel Walker'" <dwalker@codeaurora.org>,
"'Jonathan Corbet'" <corbet@lwn.net>,
"'Mel Gorman'" <mel@csn.ul.ie>,
"'Chunsang Jeong'" <chunsang.jeong@linaro.org>,
"'Jesse Barker'" <jesse.barker@linaro.org>,
"'KAMEZAWA Hiroyuki'" <kamezawa.hiroyu@jp.fujitsu.com>,
linux-kernel@vger.kernel.org,
"'Michal Nazarewicz'" <mina86@mina86.com>,
linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org,
"'Kyungmin Park'" <kyungmin.park@samsung.com>,
"'Ankita Garg'" <ankita@in.ibm.com>,
"'Andrew Morton'" <akpm@linux-foundation.org>,
Marek Szyprowski <m.szyprowski@samsung.com>,
linux-media@vger.kernel.org
Subject: Re: [PATCH 6/8] drivers: add Contiguous Memory Allocator
Date: Wed, 6 Jul 2011 11:05:00 -0500 (CDT) [thread overview]
Message-ID: <alpine.DEB.2.00.1107061100290.17624@router.home> (raw)
In-Reply-To: <20110706154857.GG8286@n2100.arm.linux.org.uk>
On Wed, 6 Jul 2011, Russell King - ARM Linux wrote:
> > > they typically don't fall into the highmem zone. As the dmabounce
> > > code allocates from the DMA coherent allocator to provide it with
> > > guaranteed DMA-able memory, that would be rather inconvenient.
> >
> > True. The dmabounce code would consequently have to allocate
> > the memory through an internal function that avoids the
> > contiguous allocation area and goes straight to ZONE_DMA memory
> > as it does today.
>
> CMA's whole purpose for existing is to provide _dma-able_ contiguous
> memory for things like cameras and such like found on crippled non-
> scatter-gather hardware. If that memory is not DMA-able what's the
> point?
ZONE_DMA is a zone for memory of legacy (crippled) devices that cannot DMA
into all of memory (and so is ZONE_DMA32). Memory from ZONE_NORMAL can be
used for DMA as well and a fully capable device would be expected to
handle any memory in the system for DMA transfers.
"guaranteed" dmaable memory? DMA abilities are device specific. Well maybe
you can call ZONE_DMA memory to be guaranteed if you guarantee that any
device must at mininum be able to perform DMA into ZONE_DMA memory. But
there may not be much of that memory around so you would want to limit
the use of that scarce resource.
next prev parent reply other threads:[~2011-07-06 16:05 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-05 7:41 [PATCHv11 0/8] Contiguous Memory Allocator Marek Szyprowski
2011-07-05 7:41 ` [PATCH 1/8] mm: move some functions from memory_hotplug.c to page_isolation.c Marek Szyprowski
2011-07-05 11:27 ` Arnd Bergmann
2011-07-05 7:41 ` [PATCH 2/8] mm: alloc_contig_freed_pages() added Marek Szyprowski
2011-07-05 11:30 ` Arnd Bergmann
2011-07-05 7:41 ` [PATCH 3/8] mm: alloc_contig_range() added Marek Szyprowski
2011-07-05 11:31 ` Arnd Bergmann
2011-07-05 7:41 ` [PATCH 4/8] mm: MIGRATE_CMA migration type added Marek Szyprowski
2011-07-05 11:44 ` Arnd Bergmann
2011-07-05 12:27 ` Russell King - ARM Linux
2011-07-05 7:41 ` [PATCH 5/8] mm: MIGRATE_CMA isolation functions added Marek Szyprowski
2011-07-05 11:45 ` Arnd Bergmann
2011-07-05 7:41 ` [PATCH 6/8] drivers: add Contiguous Memory Allocator Marek Szyprowski
2011-07-05 10:24 ` Marek Szyprowski
2011-07-05 11:02 ` [PATCH 6/8 RESEND] " Marek Szyprowski
2011-07-05 11:50 ` Arnd Bergmann
2011-07-05 11:33 ` [PATCH 6/8] " Russell King - ARM Linux
2011-07-05 12:27 ` Arnd Bergmann
2011-07-05 12:30 ` Russell King - ARM Linux
2011-07-05 13:58 ` Arnd Bergmann
2011-07-08 17:25 ` Russell King - ARM Linux
2011-07-12 13:39 ` Arnd Bergmann
2011-08-03 17:43 ` James Bottomley
2011-09-26 12:06 ` Marek Szyprowski
2011-09-26 13:00 ` Russell King - ARM Linux
2011-07-06 13:58 ` Marek Szyprowski
2011-07-06 14:09 ` Arnd Bergmann
2011-07-06 14:23 ` Russell King - ARM Linux
2011-07-06 14:37 ` [Linaro-mm-sig] " Nicolas Pitre
2011-07-06 14:59 ` Arnd Bergmann
2011-07-09 14:57 ` Janusz Krzysztofik
2011-07-11 13:47 ` Marek Szyprowski
2011-07-11 19:01 ` Janusz Krzysztofik
2011-07-12 5:34 ` Marek Szyprowski
2011-07-06 14:51 ` Arnd Bergmann
2011-07-06 15:48 ` Russell King - ARM Linux
2011-07-06 16:05 ` Christoph Lameter [this message]
2011-07-06 16:09 ` Michal Nazarewicz
2011-07-06 16:19 ` Christoph Lameter
2011-07-06 17:15 ` Russell King - ARM Linux
2011-07-06 19:03 ` Christoph Lameter
2011-07-06 17:02 ` Russell King - ARM Linux
2011-07-06 16:31 ` Arnd Bergmann
2011-07-06 19:10 ` Nicolas Pitre
2011-07-06 20:23 ` [Linaro-mm-sig] " Arnd Bergmann
2011-07-07 5:29 ` Nicolas Pitre
2011-07-06 14:56 ` Marek Szyprowski
2011-07-06 15:37 ` Russell King - ARM Linux
2011-07-06 15:47 ` Marek Szyprowski
2011-07-14 12:29 ` Marek Szyprowski
2011-07-05 7:41 ` [PATCH 7/8] ARM: integrate CMA with dma-mapping subsystem Marek Szyprowski
2011-07-05 11:50 ` Arnd Bergmann
2011-07-05 7:41 ` [PATCH 8/8] ARM: S5PV210: example of CMA private area for FIMC device on Goni board Marek Szyprowski
2011-07-05 11:51 ` Arnd Bergmann
2011-07-05 12:07 ` [PATCHv11 0/8] Contiguous Memory Allocator Arnd Bergmann
2011-07-05 12:28 ` Russell King - ARM Linux
2011-07-06 22:11 ` Andrew Morton
2011-07-07 7:36 ` Arnd Bergmann
2011-07-11 13:24 ` Marek Szyprowski
2011-07-20 8:57 [PATCHv12 " Marek Szyprowski
2011-07-20 8:57 ` [PATCH 6/8] drivers: add " Marek Szyprowski
2011-08-19 14:27 [PATCHv15 0/8] " Marek Szyprowski
2011-08-19 14:27 ` [PATCH 6/8] drivers: add " Marek Szyprowski
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