linux-kernel - Re: [PATCH] arm64/dma-mapping: Add DMA_ATTR_ALLOC_SINGLE

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Date:	Thu, 3 Mar 2016 09:44:48 -0800
From:	Doug Anderson <dianders@...omium.org>
To:	Yong Wu <yong.wu@...iatek.com>
Cc:	Joerg Roedel <joro@...tes.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Robin Murphy <robin.murphy@....com>,
	Daniel Kurtz <djkurtz@...gle.com>,
	Tomasz Figa <tfiga@...gle.com>, Arnd Bergmann <arnd@...db.de>,
	Lucas Stach <l.stach@...gutronix.de>,
	"moderated list:ARM/Mediatek SoC support" 
	<linux-mediatek@...ts.infradead.org>, srv_heupstream@...iatek.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	iommu@...ts.linux-foundation.org,
	Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH] arm64/dma-mapping: Add DMA_ATTR_ALLOC_SINGLE_PAGES support

Hi,

On Wed, Mar 2, 2016 at 10:54 AM, Yong Wu <yong.wu@...iatek.com> wrote:
> Sometimes it is not worth for the iommu allocating big chunks.
> Here we enable DMA_ATTR_ALLOC_SINGLE_PAGES which could help avoid to
> allocate big chunks while iommu allocating buffer.
>
> More information about this attribute, please check Doug's commit[1].
>
> [1]: https://lkml.org/lkml/2016/1/11/720
>
> Cc: Robin Murphy <robin.murphy@....com>
> Suggested-by: Douglas Anderson <dianders@...omium.org>
> Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> ---
>
> Our video drivers may soon use this.
>
>  arch/arm64/mm/dma-mapping.c |  4 ++--
>  drivers/iommu/dma-iommu.c   | 14 ++++++++++----
>  include/linux/dma-iommu.h   |  4 ++--
>  3 files changed, 14 insertions(+), 8 deletions(-)

It should also be mentioned that this depends on commit df05c6f6e0bb
("ARM: 8506/1: common: DMA-mapping: add DMA_ATTR_ALLOC_SINGLE_PAGES
attribute") which is not in mainline quite yet.

Also please CC Marek Szyprowski on any future patches in this area
since I saw a patch series from him that was touching this same area.

Reviewed-by: Douglas Anderson <dianders@...omium.org>