ARM: dma-mapping: add support for DMA_ATTR_NO_KERNEL_MAPPING attribute
This patch adds support for DMA_ATTR_NO_KERNEL_MAPPING attribute for
IOMMU allocations, what let drivers to save precious kernel virtual
address space for large buffers that are intended to be accessed only
from userspace.
This patch is heavily based on initial work kindly provided by Abhinav
Kochhar <abhinav.k@samsung.com>.
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Kyungmin Park <kyungmin.park@samsung.com>
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index cbdeaf4..8e505b9 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -1074,10 +1074,13 @@
return 0;
}
-static struct page **__iommu_get_pages(void *cpu_addr)
+static struct page **__iommu_get_pages(void *cpu_addr, struct dma_attrs *attrs)
{
struct vm_struct *area;
+ if (dma_get_attr(DMA_ATTR_NO_KERNEL_MAPPING, attrs))
+ return cpu_addr;
+
area = find_vm_area(cpu_addr);
if (area && (area->flags & VM_ARM_DMA_CONSISTENT))
return area->pages;
@@ -1102,6 +1105,9 @@
if (*handle == DMA_ERROR_CODE)
goto err_buffer;
+ if (dma_get_attr(DMA_ATTR_NO_KERNEL_MAPPING, attrs))
+ return pages;
+
addr = __iommu_alloc_remap(pages, size, gfp, prot,
__builtin_return_address(0));
if (!addr)
@@ -1122,7 +1128,7 @@
{
unsigned long uaddr = vma->vm_start;
unsigned long usize = vma->vm_end - vma->vm_start;
- struct page **pages = __iommu_get_pages(cpu_addr);
+ struct page **pages = __iommu_get_pages(cpu_addr, attrs);
vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot);
@@ -1149,7 +1155,7 @@
void arm_iommu_free_attrs(struct device *dev, size_t size, void *cpu_addr,
dma_addr_t handle, struct dma_attrs *attrs)
{
- struct page **pages = __iommu_get_pages(cpu_addr);
+ struct page **pages = __iommu_get_pages(cpu_addr, attrs);
size = PAGE_ALIGN(size);
if (!pages) {
@@ -1157,8 +1163,10 @@
return;
}
- unmap_kernel_range((unsigned long)cpu_addr, size);
- vunmap(cpu_addr);
+ if (!dma_get_attr(DMA_ATTR_NO_KERNEL_MAPPING, attrs)) {
+ unmap_kernel_range((unsigned long)cpu_addr, size);
+ vunmap(cpu_addr);
+ }
__iommu_remove_mapping(dev, handle, size);
__iommu_free_buffer(dev, pages, size);