From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: 'Kyungmin Park' <kmpark@infradead.org>,
'Michal Nazarewicz' <m.nazarewicz@samsung.com>,
linux-arm-kernel@lists.infradead.org,
'Daniel Walker' <dwalker@codeaurora.org>,
'Johan MOSSBERG' <johan.xx.mossberg@stericsson.com>,
'Mel Gorman' <mel@csn.ul.ie>,
linux-kernel@vger.kernel.org,
'Michal Nazarewicz' <mina86@mina86.com>,
linux-mm@kvack.org, 'Ankita Garg' <ankita@in.ibm.com>,
'Andrew Morton' <akpm@linux-foundation.org>,
linux-media@vger.kernel.org,
'KAMEZAWA Hiroyuki' <kamezawa.hiroyu@jp.fujitsu.com>
Subject: Re: [PATCHv8 00/12] Contiguous Memory Allocator
Date: Thu, 23 Dec 2010 12:19:18 +0000 [thread overview]
Message-ID: <20101223121917.GG3636@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <00ea01cba290$4d67f500$e837df00$%szyprowski@samsung.com>
On Thu, Dec 23, 2010 at 11:58:08AM +0100, Marek Szyprowski wrote:
> Actually this contiguous memory allocator is a better replacement for
> alloc_pages() which is used by dma_alloc_coherent(). It is a generic
> framework that is not tied only to ARM architecture.
... which is open to abuse. What I'm trying to find out is - if it
can't be used for DMA, what is it to be used for?
Or are we inventing an everything-but-ARM framework?
> > In other words, do we _actually_ have a use for this which doesn't
> > involve doing something like allocating 32MB of memory from it,
> > remapping it so that it's DMA coherent, and then performing DMA
> > on the resulting buffer?
>
> This is an arm specific problem, also related to dma_alloc_coherent()
> allocator. To be 100% conformant with ARM specification we would
> probably need to unmap all pages used by the dma_coherent allocator
> from the LOW MEM area. This is doable, but completely not related
> to the CMA and this patch series.
You've already been told why we can't unmap pages from the kernel
direct mapping.
Okay, so I'm just going to assume that CMA has _no_ _business_ being
used on ARM, and is not something that should interest anyone in the
ARM community.
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next prev parent reply other threads:[~2010-12-23 12:20 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-15 20:34 Michal Nazarewicz
2010-12-15 20:34 ` [PATCHv8 01/12] mm: migrate.c: fix compilation error Michal Nazarewicz
2010-12-15 20:34 ` [PATCHv8 02/12] lib: bitmap: Added alignment offset for bitmap_find_next_zero_area() Michal Nazarewicz
2010-12-15 20:34 ` [PATCHv8 03/12] lib: genalloc: Generic allocator improvements Michal Nazarewicz
2010-12-15 20:34 ` [PATCHv8 04/12] mm: move some functions from memory_hotplug.c to page_isolation.c Michal Nazarewicz
2010-12-15 20:34 ` [PATCHv8 05/12] mm: alloc_contig_freed_pages() added Michal Nazarewicz
2010-12-15 20:34 ` [PATCHv8 06/12] mm: alloc_contig_range() added Michal Nazarewicz
2010-12-15 20:34 ` [PATCHv8 07/12] mm: cma: Contiguous Memory Allocator added Michal Nazarewicz
2011-02-02 12:43 ` Ankita Garg
2011-02-02 14:58 ` Michal Nazarewicz
2010-12-15 20:34 ` [PATCHv8 08/12] mm: MIGRATE_CMA migration type added Michal Nazarewicz
2010-12-15 20:34 ` [PATCHv8 09/12] mm: MIGRATE_CMA isolation functions added Michal Nazarewicz
2010-12-15 20:34 ` [PATCHv8 10/12] mm: MIGRATE_CMA support added to CMA Michal Nazarewicz
2010-12-15 20:34 ` [PATCHv8 11/12] mm: cma: Test device and application added Michal Nazarewicz
2010-12-15 20:34 ` [PATCHv8 12/12] ARM: cma: Added CMA to Aquila, Goni and c210 universal boards Michal Nazarewicz
2010-12-23 9:30 ` [PATCHv8 00/12] Contiguous Memory Allocator Kyungmin Park
2010-12-23 10:06 ` Russell King - ARM Linux
2010-12-23 10:58 ` Marek Szyprowski
2010-12-23 12:19 ` Russell King - ARM Linux [this message]
2010-12-23 13:09 ` Marek Szyprowski
2010-12-23 13:44 ` Russell King - ARM Linux
2011-01-12 18:49 ` Marek Szyprowski
2011-01-12 19:04 ` Nicolas Pitre
2011-01-13 7:01 ` Marek Szyprowski
2010-12-23 13:35 ` Tomasz Fujak
2010-12-23 13:48 ` Russell King - ARM Linux
2010-12-23 14:04 ` Tomasz Fujak
2010-12-23 14:16 ` Russell King - ARM Linux
2010-12-23 14:42 ` Felipe Contreras
2010-12-23 15:02 ` Michal Nazarewicz
2010-12-23 18:04 ` David Brown
2010-12-23 13:41 ` Michal Nazarewicz
2010-12-23 13:51 ` Russell King - ARM Linux
2010-12-23 14:08 ` Tomasz Fujak
2010-12-23 14:20 ` Russell King - ARM Linux
2010-12-23 15:35 ` Tomasz Fujak
2011-01-04 23:12 ` Jamie Lokier
2011-01-04 16:23 ` Johan MOSSBERG
2011-01-04 16:59 ` Michał Nazarewicz
2011-01-04 17:19 ` Russell King - ARM Linux
2011-01-04 17:31 ` Santosh Shilimkar
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