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Subject: RE: [PATCH 7/9] ARM: DMA: steal memory for DMA coherent mappings
From: Tixy <tixy@yxit.co.uk>
To: Marek Szyprowski <m.szyprowski@samsung.com>
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Date: Thu, 18 Aug 2011 09:27:53 +0100
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On Wed, 2011-08-17 at 15:06 +0200, Marek Szyprowski wrote:
[...]
> > > Maybe for the first version a static pool with reasonably small size
> > > (like 128KiB) will be more than enough? This size can be even board
> > > depended or changed with kernel command line for systems that really
> > > needs more memory.
> > 
> > For a first version that sounds good enough. Maybe we could use a fraction
> > of the CONSISTENT_DMA_SIZE as an estimate?
> 
> Ok, good. For the initial values I will probably use 1/8 of 
> CONSISTENT_DMA_SIZE for coherent allocations. Writecombine atomic allocations
> are extremely rare and rather ARM specific. 1/32 of CONSISTENT_DMA_SIZE should
> be more than enough for them.

For people who aren't aware, we have a patch to remove the define
CONSISTENT_DMA_SIZE and replace it with a runtime call to an
initialisation function [1]. I don't believe this fundamentally changes
anything being discussed though.

-- 
Tixy

[1] http://www.spinics.net/lists/arm-kernel/msg135589.html