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Date:   Tue, 24 Apr 2018 09:56:45 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Russell King - ARM Linux <linux@armlinux.org.uk>
Cc:     Christoph Hellwig <hch@lst.de>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
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Subject: Re: [PATCH 11/12] swiotlb: move the SWIOTLB config symbol to
        lib/Kconfig
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On Tue, Apr 24, 2018 at 08:47:27AM +0100, Russell King - ARM Linux wrote:
> Therefore, the default state for SWIOTLB and hence NEED_SG_DMA_LENGTH
> becomes 'y' on ARM, and any defconfig file that does not mention SWIOTLB
> explicitly ends up with both these enabled.

Indeed, sorry.

> It does look a bit weird though - patch 10 arranged stuff so that we
> didn't end up with SWIOTLB always enabled, but this patch reintroduces
> that with the allowance that the user can disable if so desired.

I am not very happy with that patch, but I have a hard time coming
up with something saner.

Bascially x86_64 and mips/loongson default to SWIOTLB=y but allow to
deselect it, powerpc has it optional without any real dependency
and defaults to n and everyone just selects it otherwise.

I suspect the right thing is to just have it always one for x86_64
and loongson and have a ppc-specific option to enable it on powerpc
so that we can always use select statements.  I'll do that for the
next round.