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SubjectRe: [PATCH 09/10] swiotlb: add support for non-coherent DMA
On Mon, Oct 08, 2018 at 10:02:45AM +0200, Christoph Hellwig wrote:
> Handle architectures that are not cache coherent directly in the main
> swiotlb code by calling arch_sync_dma_for_{device,cpu} in all the right
> places from the various dma_map/unmap/sync methods when the device is
> non-coherent.
>
> Because swiotlb now uses dma_direct_alloc for the coherent allocation
> that side is already taken care of by the dma-direct code calling into
> arch_dma_{alloc,free} for devices that are non-coherent.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

Thank you!
> ---
> kernel/dma/swiotlb.c | 23 +++++++++++++++++------
> 1 file changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> index 475a41eff3dc..52885b274368 100644
> --- a/kernel/dma/swiotlb.c
> +++ b/kernel/dma/swiotlb.c
> @@ -21,6 +21,7 @@
>
> #include <linux/cache.h>
> #include <linux/dma-direct.h>
> +#include <linux/dma-noncoherent.h>
> #include <linux/mm.h>
> #include <linux/export.h>
> #include <linux/spinlock.h>
> @@ -677,6 +678,10 @@ dma_addr_t swiotlb_map_page(struct device *dev, struct page *page,
> dma_addr = swiotlb_bounce_page(dev, &phys, size, dir, attrs);
> }
>
> + if (!dev_is_dma_coherent(dev) &&
> + (attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
> + arch_sync_dma_for_device(dev, phys, size, dir);
> +
> return dma_addr;
> }
>
> @@ -696,6 +701,10 @@ void swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
>
> BUG_ON(dir == DMA_NONE);
>
> + if (!dev_is_dma_coherent(hwdev) &&
> + (attrs & DMA_ATTR_SKIP_CPU_SYNC) == 0)
> + arch_sync_dma_for_cpu(hwdev, paddr, size, dir);
> +
> if (is_swiotlb_buffer(paddr)) {
> swiotlb_tbl_unmap_single(hwdev, paddr, size, dir, attrs);
> return;
> @@ -732,15 +741,17 @@ swiotlb_sync_single(struct device *hwdev, dma_addr_t dev_addr,
>
> BUG_ON(dir == DMA_NONE);
>
> - if (is_swiotlb_buffer(paddr)) {
> + if (!dev_is_dma_coherent(hwdev) && target == SYNC_FOR_CPU)
> + arch_sync_dma_for_cpu(hwdev, paddr, size, dir);
> +
> + if (is_swiotlb_buffer(paddr))
> swiotlb_tbl_sync_single(hwdev, paddr, size, dir, target);
> - return;
> - }
>
> - if (dir != DMA_FROM_DEVICE)
> - return;
> + if (!dev_is_dma_coherent(hwdev) && target == SYNC_FOR_DEVICE)
> + arch_sync_dma_for_device(hwdev, paddr, size, dir);
>
> - dma_mark_clean(phys_to_virt(paddr), size);
> + if (!is_swiotlb_buffer(paddr) && dir == DMA_FROM_DEVICE)
> + dma_mark_clean(phys_to_virt(paddr), size);
> }
>
> void
> --
> 2.19.0
>

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