linux-kernel - Re: [PATCH] powerpc: remove IOMMU

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Date:	Wed, 03 Mar 2010 11:13:52 +1100
From:	Michael Ellerman <michael@...erman.id.au>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Cc:	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
	benh@...nel.crashing.or, arnd@...db.de, davem@...emloft.net
Subject: Re: [PATCH] powerpc: remove IOMMU_VMERGE config option

On Wed, 2010-03-03 at 08:54 +0900, FUJITA Tomonori wrote:
> Seems that IOMMU_VMERGE option description gives the false
> information:
> 
> http://marc.info/?l=linux-sparc&m=126753808727669&w=2
> http://marc.info/?l=linux-sparc&m=126753880528825&w=2
> 
> IOMMU_VMERGE is unnecessary nowadays so how about removing it?

Except you didn't remove it, you just made it uneditable? Why not get
rid of it entirely.

cheers

> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 155d571..2dfa83b 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -314,17 +314,8 @@ config 8XX_MINIMAL_FPEMU
>  	  It is recommended that you build a soft-float userspace instead.
>  
>  config IOMMU_VMERGE
> -	bool "Enable IOMMU virtual merging"
> +	def_bool y
>  	depends on PPC64
> -	default y
> -	help
> -	  Cause IO segments sent to a device for DMA to be merged virtually
> -	  by the IOMMU when they happen to have been allocated contiguously.
> -	  This doesn't add pressure to the IOMMU allocator. However, some
> -	  drivers don't support getting large merged segments coming back
> -	  from *_map_sg().
> -
> -	  Most drivers don't have this problem; it is safe to say Y here.
>  
>  config IOMMU_HELPER
>  	def_bool PPC64



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