From: Christoph Hellwig <hch@lst.de>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Vladimir Murzin <vladimir.murzin@arm.com>,
Christoph Hellwig <hch@lst.de>,
Vitaly Kuzmichev <vitaly_kuzmichev@mentor.com>,
gregkh@linuxfoundation.org, m.szyprowski@samsung.com,
linux-kernel@vger.kernel.org, linux-next@vger.kernel.org,
"George G. Davis" <george_davis@mentor.com>
Subject: Re: [PATCH v2 1/2] drivers: dma-coherent: Fix dev->cma_area vs dev->dma_mem breakage
Date: Tue, 11 Jul 2017 16:19:37 +0200 [thread overview]
Message-ID: <20170711141937.GA12884@lst.de> (raw)
In-Reply-To: <6f26f0d9-506a-76bf-1410-19b00162c4a1@arm.com>
On Fri, Jul 07, 2017 at 05:06:52PM +0100, Robin Murphy wrote:
> I don't think we need to go that far, I reckon it would be clear enough
> to just split the per-device vs. global pool interfaces, something like
> I've sketched out below (such that the ops->alloc implementation calls
> dma_alloc_from_global_coherent() if dma_alloc_from_contiguous() fails).
>
> If anyone wants to take that and run with it, feel free.
I like this basic idea. It also fits into one of my plans for the
4.14 merge window - I want to enhance the lib/dma-noop.c so that
it can use different allocators and mapping helpers, e.g. for
the allocators what makes sense is:
(1) simple page allocator (as-is)
(2) CMA
(3) swiotlb
(4) the OF coherent allocator from your draft patch
and then for the mapping into phys space we can use
(1) virto_to_phys (as-is)
(2) arch helper (e.g. like done in mips plat support)
(3) maybe some common form of ioremap / vmap instead of various
duplicates
With that we should be able to cosolidate most direct mapped
dma_ops for architectures that do not require cache flushing into
common code. As a next step we could think about useful cache
flushing hooks.
next prev parent reply other threads:[~2017-07-11 14:19 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-03 14:51 [PATCH 0/2] Implement default DMA coherent pool vitaly_kuzmichev
2017-07-03 14:51 ` [PATCH 1/2] drivers: dma-coherent: Add support for " vitaly_kuzmichev
2017-07-04 21:02 ` kbuild test robot
2017-07-05 5:55 ` kbuild test robot
2017-07-10 0:36 ` Rob Herring
2017-07-03 14:51 ` [PATCH 2/2] drivers: dma-coherent: show per-device DMA region utilization via procfs vitaly_kuzmichev
2017-07-07 13:22 ` [PATCH v2 0/2] Additions to default DMA coherent pool Vitaly Kuzmichev
2017-07-07 13:22 ` [PATCH v2 1/2] drivers: dma-coherent: Fix dev->cma_area vs dev->dma_mem breakage Vitaly Kuzmichev
2017-07-07 14:27 ` Christoph Hellwig
2017-07-07 15:40 ` Vladimir Murzin
2017-07-07 16:06 ` Robin Murphy
2017-07-07 16:44 ` Vladimir Murzin
2017-07-07 17:55 ` Robin Murphy
2017-07-10 13:42 ` Vladimir Murzin
2017-07-11 14:19 ` Christoph Hellwig [this message]
2017-07-07 13:23 ` [PATCH v2 2/2] drivers: dma-coherent: show per-device DMA region utilization via procfs Vitaly Kuzmichev
2017-07-07 14:28 ` Christoph Hellwig
2017-07-07 13:55 ` [PATCH v2 0/2] Additions to default DMA coherent pool Stephen Rothwell
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