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Re: some question about wmb in mips

To: Ralf Baechle <ralf@linux-mips.org>
Subject: Re: some question about wmb in mips
From: David Daney <ddaney@caviumnetworks.com>
Date: Tue, 31 Aug 2010 08:59:43 -0700
Cc: loody <miloody@gmail.com>, "Maciej W. Rozycki" <macro@linux-mips.org>, Linux MIPS Mailing List <linux-mips@linux-mips.org>
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On 08/31/2010 07:33 AM, Ralf Baechle wrote:
On Mon, Aug 30, 2010 at 09:58:27PM +0800, loody wrote:

after reading the DMA api document and check the source code.
I found mips seems not implement "dma map ops", but x86 has implemented it.
What are they used for and why mips don't implement it?

This is useful for multiple sets of methods on more complicated systems.
Right now we just don't need that.


That said, I am preparing a set of patches that converts MIPS to use struct dma_map_ops. They turn out to be useful in systems where PCI devices need different treatment than on-chip devices, and when bounce buffers are needed form some devices, but not others.

David Daney

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