linux-kernel - Re: [PATCH V4 1/3] x86: introduce CONFIG_X86_DEV_DMA

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Date:	Thu, 12 Apr 2012 13:18:20 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Alessandro Rubini <rubini@...dd.com>
CC:	mingo@...e.hu, akpm@...ux-foundation.org, jbarnes@...tuousgeek.org,
	fujita.tomonori@....ntt.co.jp, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, mingo@...hat.com, x86@...nel.org,
	giancarlo.asnaghi@...com, alan@...ux.intel.com
Subject: Re: [PATCH V4 1/3] x86: introduce CONFIG_X86_DEV_DMA_OPS

On 04/12/2012 01:15 PM, Alessandro Rubini wrote:
> 
> The current approach is using swiotlb and it works pretty well, though
> with a limit of 4MB of swiotlb area.  I've been considering use of the
> DMA zone to this aim: internally I have some half-working thing that
> resuses the ISA DMA zone for our own aims, raising the DMA limit to
> 512MB.
> 
> Do you think the approach may make sense? I use this basic
> thing in Kconfig, to rely on GFP_DMA for the rest:
> 
>   config MAX_DMA_PADDR
>           int
>           default 536870912 if MAX_DMA_PADDR_512M
>           default 16777216
> 
>   config MAX_DMA_PADDR_512M
>           bool
> 
> (actually, we'd benefit from being able to use hex in defaults)
> 
> Is this worth exploring, to possibly submit a patch in this direction?
> 

Not as a compile-time patch.

	-hpa


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