arm: Add option to skip buffer zeroing

The DMA framework currently zeros all buffers because it (righfully so)
assumes that drivers will soon need to pass the memory to a device.
Some devices/use case may not require zeroed memory and there can
be an increase in performance if we skip the zeroing. Add a DMA_ATTR
to allow skipping of DMA zeroing.

Change-Id: Ib78a19cb341c3c441f91d5b004c6375c80c10413
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
[pdaly@codeaurora.org Resolve minor conflicts]
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 8fa0ef2..d419f04 100644 (file)
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -310,7 +310,8 @@ static void __dma_free_buffer(struct page *page, size_t size)
 
 static void *__alloc_from_contiguous(struct device *dev, size_t size,
                                     pgprot_t prot, struct page **ret_page,
-                                    const void *caller, bool want_vaddr);
+                                    const void *caller,
+                                    struct dma_attrs *attrs);
 
 static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t gfp,
                                 pgprot_t prot, struct page **ret_page,
@@ -378,7 +379,7 @@ static int __init atomic_pool_init(void)
 
        if (dev_get_cma_area(NULL))
                ptr = __alloc_from_contiguous(NULL, atomic_pool_size, prot,
-                                             &page, atomic_pool_init, true);
+                               &page, atomic_pool_init, NULL);
        else
                ptr = __alloc_remap_buffer(NULL, atomic_pool_size, gfp, prot,
                                           &page, atomic_pool_init, true);
@@ -560,18 +561,22 @@ static int __free_from_pool(void *start, size_t size)
 
 static void *__alloc_from_contiguous(struct device *dev, size_t size,
                                     pgprot_t prot, struct page **ret_page,
-                                    const void *caller, bool want_vaddr)
+                                    const void *caller,
+                                    struct dma_attrs *attrs)
 {
        unsigned long order = get_order(size);
        size_t count = size >> PAGE_SHIFT;
        struct page *page;
        void *ptr = NULL;
+       bool want_vaddr = !dma_get_attr(DMA_ATTR_NO_KERNEL_MAPPING,
+                                                       attrs);
 
        page = dma_alloc_from_contiguous(dev, count, order);
        if (!page)
                return NULL;
 
-       __dma_clear_buffer(page, size);
+       if (!dma_get_attr(DMA_ATTR_SKIP_ZEROING, attrs))
+               __dma_clear_buffer(page, size);
 
        if (!want_vaddr)
                goto out;
@@ -688,7 +693,7 @@ static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
                addr = __alloc_simple_buffer(dev, size, gfp, &page);
        else if (dev_get_cma_area(dev) && (gfp & __GFP_DIRECT_RECLAIM))
                addr = __alloc_from_contiguous(dev, size, prot, &page,
-                                              caller, want_vaddr);
+                                              caller, attrs);
        else if (is_coherent)
                addr = __alloc_simple_buffer(dev, size, gfp, &page);
        else if (!gfpflags_allow_blocking(gfp))