Re: [PATCH] powerpc: use the generic dma coherent remap allocator

[Christoph Hellwig <hch@lst.de>]

On Wed, Aug 14, 2019 at 04:20:34PM +0200, Christophe Leroy wrote:
>> index 56a7c814160d..afe71b89dec3 100644
>> --- a/arch/powerpc/platforms/Kconfig.cputype
>> +++ b/arch/powerpc/platforms/Kconfig.cputype
>> @@ -450,8 +450,10 @@ config NOT_COHERENT_CACHE
>>   	depends on 4xx || PPC_8xx || E200 || PPC_MPC512x || \
>>   		GAMECUBE_COMMON || AMIGAONE
>>   	select ARCH_HAS_DMA_COHERENT_TO_PFN
>
> You drop arch_dma_coherent_to_pfn(), it's surprising to see 
> ARCH_HAS_DMA_COHERENT_TO_PFN remains. At first I thought I'd get a build 
> failure.
>
> After looking more, I see there is a arch_dma_coherent_to_pfn()
> defined in kernel/dma/remap.c when DMA_DIRECT_REMAP is selected.
>
> I think the naming is not really consistant and should be fixed some how, 
> because that's misleading to have an arch_something() being common to all.

I actually have patches in the queue kill arch_dma_coherent_to_pfn off
entirely, as we can always just get back to the physical address and thus
pfn from the dma address using dma_to_phys for dma-direct.

But there is a huge review backlog for my outstanding dma patcheset,
so it might take a bit until it is posted.