RE: [PATCH 8/9] dspbridge: add map support for big buffers

[Guzman Lugo, Fernando]

________________________________________
>From: FUJITA Tomonori [fujita.tomonori@xxxxxxxxxxxxx]
>Sent: Thursday, August 26, 2010 9:03 AM
>To: Guzman Lugo, Fernando
>Cc: fujita.tomonori@xxxxxxxxxxxxx; linux-omap@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; ohad@xxxxxxxxxx; hiroshi.doyu@xxxxxxxxx; ameya.palande@xxxxxxxxx; >felipe.contreras@xxxxxxxxx
>Subject: RE: [PATCH 8/9] dspbridge: add map support for big buffers
>
>On Thu, 26 Aug 2010 08:16:24 -0500
>"Guzman Lugo, Fernando" <fernando.lugo@xxxxxx> wrote:
>
>> >From a quick look, arch/arm/plat-omap/iovmm.c does nothing wrong about
>> >scatter gather chaining. arm/arm/mm/dma-mapping.c looks fine too about
>> >it. Maybe just defining ARCH_HAS_SG_CHAIN works?
>>
>> I can try, but it looks tricky for me. Maybe someone else can tell us why
>> SG chain is not supported for ARM or if there is a problem just defining
>> ARCH_HAS_SG_CHAIN.
>
>I suppose that nobody in ARM has been interested in the feature. It
>was invented to improve I/O performance with large I/O requests. No
>wonder embeded people aren't interested in it.
>
>fujita@rose:~/git/linux-2.6$ find arch -name 'scatterlist.h'|xargs grep HAS_SG
>arch/x86/include/asm/scatterlist.h:#define ARCH_HAS_SG_CHAIN
>arch/ia64/include/asm/scatterlist.h:#define ARCH_HAS_SG_CHAIN
>arch/sparc/include/asm/scatterlist.h:#define ARCH_HAS_SG_CHAIN
>arch/powerpc/include/asm/scatterlist.h:#define ARCH_HAS_SG_CHAIN

Ok, so let me try SG chain, that should be the correct fix.

Thanks a lot,
Fernando.
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