linux-kernel - Re: [PATCH 10/10] arm64: use the generic swiotlb_dma

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Date:   Fri, 12 Oct 2018 18:05:50 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Christoph Hellwig <hch@....de>
Cc:     Robin Murphy <robin.murphy@....com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Will Deacon <will.deacon@....com>,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 10/10] arm64: use the generic swiotlb_dma_ops

On Fri, Oct 12, 2018 at 04:40:49PM +0200, Christoph Hellwig wrote:
> On Fri, Oct 12, 2018 at 02:01:00PM +0100, Robin Murphy wrote:
> > On 08/10/18 09:02, Christoph Hellwig wrote:
> >> Now that the generic swiotlb code supports non-coherent DMA we can switch
> >> to it for arm64.  For that we need to refactor the existing
> >> alloc/free/mmap/pgprot helpers to be used as the architecture hooks,
> >> and implement the standard arch_sync_dma_for_{device,cpu} hooks for
> >> cache maintaincance in the streaming dma hooks, which also implies
> >> using the generic dma_coherent flag in struct device.
> >>
> >> Note that we need to keep the old is_device_dma_coherent function around
> >> for now, so that the shared arm/arm64 Xen code keeps working.
> >
> > OK, so when I said last night that it boot-tested OK, that much was true, 
> > but then I shut the board down as I left and got a megasplosion of bad page 
> > state BUGs, e.g.:
> 
> I think this is because I am passing the wrong address to
> dma_direct_free_pages.  Please try this patch on top:
> 
> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> index 3c75d69b54e7..4f0f92856c4c 100644
> --- a/arch/arm64/mm/dma-mapping.c
> +++ b/arch/arm64/mm/dma-mapping.c
> @@ -126,10 +126,12 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
>  void arch_dma_free(struct device *dev, size_t size, void *vaddr,
>  		dma_addr_t dma_handle, unsigned long attrs)
>  {
> -	if (__free_from_pool(vaddr, PAGE_ALIGN(size)))
> -		return;
> -	vunmap(vaddr);
> -	dma_direct_free_pages(dev, size, vaddr, dma_handle, attrs);
> +	if (!__free_from_pool(vaddr, PAGE_ALIGN(size)))
> +		void *kaddr = phys_to_virt(dma_to_phys(dev, dma_handle));
> +
> +		vunmap(vaddr);
> +		dma_direct_free_pages(dev, size, kaddr, dma_handle, attrs);
> +	}
>  }
>  
>  long arch_dma_coherent_to_pfn(struct device *dev, void *cpu_addr,

With this fix:

Acked-by: Catalin Marinas <catalin.marinas@....com>