DMA allocations with the DMA_ATTR_NO_KERNEL_MAPPING do not return a kernel
virtual address for use in driver, but are expected to be used entirely
for userspace mappings and/or device private memory.
Because of that we don't need to remap them as uncached, and thus don't need
the atomic pool for non-blocking allocations. Note that using the
DMA allocator with DMA_ATTR_NO_KERNEL_MAPPING from non-blocking context
on a non-coherent device is actually broken without this patch as well, as
we feed the address passes to dma_free_attrs directly to the genpool
allocator, but for DMA_ATTR_NO_KERNEL_MAPPING allocations it actually
contains the address of the first page pointer.
Signed-off-by: Christoph Hellwig <h...@lst.de>
---
arch/arm/mm/dma-mapping.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 0a75058c11f3..30e891f54d36 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -724,6 +724,7 @@ static void *__dma_alloc(struct device *dev, size_t size,
dma_addr_t *handle,
gfp_t gfp, pgprot_t prot, bool is_coherent,
unsigned long attrs, const void *caller)
{
+ bool want_vaddr = !(attrs & DMA_ATTR_NO_KERNEL_MAPPING);
u64 mask = get_coherent_dma_mask(dev);
struct page *page = NULL;
void *addr;
@@ -735,7 +736,7 @@ static void *__dma_alloc(struct device *dev, size_t size,
dma_addr_t *handle,
.gfp = gfp,
.prot = prot,
.caller = caller,
- .want_vaddr = ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) == 0),
+ .want_vaddr = want_vaddr,
.coherent_flag = is_coherent ? COHERENT : NORMAL,
};
@@ -773,14 +774,14 @@ static void *__dma_alloc(struct device *dev, size_t size,
dma_addr_t *handle,
allowblock = gfpflags_allow_blocking(gfp);
cma = allowblock ? dev_get_cma_area(dev) : false;
- if (cma)
+ if (!allowblock && !is_coherent && want_vaddr)
+ buf->allocator = &pool_allocator;
+ else if (cma)
buf->allocator = &cma_allocator;
else if (is_coherent)
buf->allocator = &simple_allocator;
- else if (allowblock)
- buf->allocator = &remap_allocator;
else
- buf->allocator = &pool_allocator;
+ buf->allocator = &remap_allocator;
addr = buf->allocator->alloc(&args, &page);
--
2.20.1
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
