[PATCH 15/25] iommu/dma: Don't remap CMA unnecessarily

Christoph Hellwig
2019-04-30T10:55:19Z

From: Robin Murphy <robin.murphy@arm.com>

Always remapping CMA allocations was largely a bodge to keep the freeing
logic manageable when it was split between here and an arch wrapper. Now
that it's all together and streamlined, we can relax that limitation.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
drivers/iommu/dma-iommu.c | 19 ++++++++++++-------
1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 26f2d059873b..ccdd655bc03a 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -954,7 +954,6 @@ static void *iommu_dma_alloc(struct device *dev, size_t size,
{
bool coherent = dev_is_dma_coherent(dev);
int ioprot = dma_info_to_prot(DMA_BIDIRECTIONAL, coherent, attrs);
- pgprot_t prot = arch_dma_mmap_pgprot(dev, PAGE_KERNEL, attrs);
size_t iosize = size;
struct page *page;
void *addr;
@@ -1002,13 +1001,19 @@ static void *iommu_dma_alloc(struct device *dev, size_t size,
if (*handle == DMA_MAPPING_ERROR)
goto out_free_pages;

- addr = dma_common_contiguous_remap(page, size, VM_USERMAP, prot,
- __builtin_return_address(0));
- if (!addr)
- goto out_unmap;
+ if (!coherent || PageHighMem(page)) {
+ pgprot_t prot = arch_dma_mmap_pgprot(dev, PAGE_KERNEL, attrs);

- if (!coherent)
- arch_dma_prep_coherent(page, iosize);
+ addr = dma_common_contiguous_remap(page, size, VM_USERMAP, prot,
+ __builtin_return_address(0));
+ if (!addr)
+ goto out_unmap;
+
+ if (!coherent)
+ arch_dma_prep_coherent(page, iosize);
+ } else {
+ addr = page_address(page);
+ }
memset(addr, 0, size);
return addr;