Re: [PATCH 10/10] arm64: use the generic swiotlb_dma_ops

Catalin Marinas
2018-10-12T17:05:56Z

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@arm.com>