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From: Christoph Hellwig <hch@lst.de>
To: Vladimir Murzin <vladimir.murzin@arm.com>
Cc: Christoph Hellwig <hch@lst.de>,
	Vineet Gupta <vgupta@synopsys.com>,
	Jonas Bonn <jonas@southpole.se>,
	Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>,
	Stafford Horne <shorne@gmail.com>, Helge Deller <deller@gmx.de>,
	linux-snps-arc@lists.infradead.org,
	linux-arm-kernel@lists.infradead.org,
	openrisc@lists.librecores.org, linux-parisc@vger.kernel.org,
	linux-xtensa@linux-xtensa.org, iommu@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/7] arm-nommu: remove the partial DMA_ATTR_NON_CONSISTENT support
Date: Tue, 25 Jun 2019 08:13:32 +0200
Message-ID: <20190625061332.GC28986@lst.de> (raw)
In-Reply-To: <a017e704-c6c4-7718-7f8b-eb8a0eced14d@arm.com>

On Mon, Jun 24, 2019 at 03:23:08PM +0100, Vladimir Murzin wrote:
> On 6/14/19 3:44 PM, Christoph Hellwig wrote:
> > The arm-nommu DMA code supports DMA_ATTR_NON_CONSISTENT allocations, but
> > does not provide a cache_sync operation.  This means any user of it
> > will never be able to actually transfer cache ownership and thus cause
> > coherency bugs.
> 
> By the way, Documentation/DMA-attributes.txt doesn't specify cache_sync() as
> requirement for DMA_ATTR_NON_CONSISTENT it only states that it is responsibility
> of the driver to have all the correct and necessary sync points.

True.  dma_cache_sync has always been a rather odd interface, as it
doesn't specify in what direction we need to sync and doesn't
participate in our ownership protocol.  So my mid-term plan is to kill
it off and replace it with the existing dma_sync_* helpers.  This
series is the first step towards that.

  reply index

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-14 14:44 handle "special" dma allocation in common code Christoph Hellwig
2019-06-14 14:44 ` [PATCH 1/7] arm-nommu: remove the partial DMA_ATTR_NON_CONSISTENT support Christoph Hellwig
2019-06-24 14:23   ` Vladimir Murzin
2019-06-25  6:13     ` Christoph Hellwig [this message]
2019-06-14 14:44 ` [PATCH 2/7] arc: " Christoph Hellwig
2019-06-14 14:44 ` [PATCH 3/7] openrisc: " Christoph Hellwig
2019-06-16  9:17   ` Stafford Horne
2019-06-14 14:44 ` [PATCH 4/7] dma-mapping: add a dma_alloc_need_uncached helper Christoph Hellwig
2019-06-14 14:44 ` [PATCH 5/7] dma-direct: handle DMA_ATTR_NON_CONSISTENT in common code Christoph Hellwig
2019-06-25  6:11   ` Christoph Hellwig
2019-06-25 12:23   ` Helge Deller
2019-06-25 12:28     ` Christoph Hellwig
2019-06-14 14:44 ` [PATCH 6/7] dma-direct: handle DMA_ATTR_NO_KERNEL_MAPPING " Christoph Hellwig
2019-06-29 15:09   ` Guenter Roeck
2019-06-14 14:44 ` [PATCH 7/7] arc: use the generic remapping allocator for coherent DMA allocations Christoph Hellwig
2019-06-14 18:05   ` Eugeniy Paltsev
2019-06-15  8:35     ` hch

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