linux-kernel - Re: [PATCH] x86: enable DMA CMA with swiotlb

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Message-ID: <CAC5umyh0Hfx3NgHX11eqskuifhrdYGB8L1nx1u0YUdBGchRTxw@mail.gmail.com>
Date:	Fri, 22 Nov 2013 00:02:14 +0900
From:	Akinobu Mita <akinobu.mita@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org
Subject: Re: [PATCH] x86: enable DMA CMA with swiotlb

2013/11/21 H. Peter Anvin <hpa@...or.com>:
> On 11/19/2013 03:32 PM, Akinobu Mita wrote:
>> The DMA Contiguous Memory Allocator support on x86 is disabled when
>> swiotlb config option is enabled.  So DMA CMA is always disabled on
>> x86_64 because swiotlb is always enabled.  This attempts to support
>> for DMA CMA with enabling swiotlb config option.
>
> What is the use case?

I want to use DMA CMA for the feature that requires a single huge chunk
(about 64MB) of host memory.  Please refer 3 of 24 in:
http://www.jedec.org/sites/default/files/T_Fujisawa_MF_2013.pdf
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