[PATCH 09/10] swiotlb: add support for non-coherent DMA

Christoph Hellwig
2018-10-08T08:03:43Z

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>
---
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