Re: [PATCH 07/11] powerpc: make dma_cache_sync a no-op
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- To: Christophe LEROY <christophe.leroy@xxxxxx>
- Subject: Re: [PATCH 07/11] powerpc: make dma_cache_sync a no-op
- From: Christoph Hellwig <hch@xxxxxx>
- Date: Tue, 3 Oct 2017 13:43:30 +0200
- Cc: Christoph Hellwig <hch@xxxxxx>, iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx, Chris Zankel <chris@xxxxxxxxxx>, Michal Simek <monstr@xxxxxxxxx>, linux-ia64@xxxxxxxxxxxxxxx, linux-mips@xxxxxxxxxxxxxx, linux-sh@xxxxxxxxxxxxxxx, linuxppc-dev@xxxxxxxxxxxxxxxx, linux-xtensa@xxxxxxxxxxxxxxxx, x86@xxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, David Howells <dhowells@xxxxxxxxxx>, Max Filippov <jcmvbkbc@xxxxxxxxx>, Guan Xuetao <gxt@xxxxxxxxxxxxxxx>, Robin Murphy <robin.murphy@xxxxxxx>, Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
- In-reply-to: <670a0571-1a36-51a3-db52-64bc61184c35@c-s.fr>
- References: <20171003104311.10058-1-hch@lst.de> <20171003104311.10058-8-hch@lst.de> <670a0571-1a36-51a3-db52-64bc61184c35@c-s.fr>
- User-agent: Mutt/1.5.17 (2007-11-01)
On Tue, Oct 03, 2017 at 01:24:57PM +0200, Christophe LEROY wrote:
>> powerpc does not implement DMA_ATTR_NON_CONSISTENT allocations, so it
>> doesn't make any sense to do any work in dma_cache_sync given that it
>> must be a no-op when dma_alloc_attrs returns coherent memory.
> What about arch/powerpc/mm/dma-noncoherent.c ?
>
> Powerpc 8xx doesn't have coherent memory.
It doesn't implement the DMA_ATTR_NON_CONSISTENT interface either,
so if it really doesn't have a way to provide dma coherent allocation
(although the code in __dma_alloc_coherent suggests it does provide
dma coherent allocations) I have no idea how it could ever have
worked.
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