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-rw-r--r--lib/dma-direct.c156
1 files changed, 156 insertions, 0 deletions
diff --git a/lib/dma-direct.c b/lib/dma-direct.c
new file mode 100644
index 000000000000..40b1f92f2214
--- /dev/null
+++ b/lib/dma-direct.c
@@ -0,0 +1,156 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * DMA operations that map physical memory directly without using an IOMMU or
+ * flushing caches.
+ */
+#include <linux/export.h>
+#include <linux/mm.h>
+#include <linux/dma-direct.h>
+#include <linux/scatterlist.h>
+#include <linux/dma-contiguous.h>
+#include <linux/pfn.h>
+
+#define DIRECT_MAPPING_ERROR 0
+
+/*
+ * Most architectures use ZONE_DMA for the first 16 Megabytes, but
+ * some use it for entirely different regions:
+ */
+#ifndef ARCH_ZONE_DMA_BITS
+#define ARCH_ZONE_DMA_BITS 24
+#endif
+
+static bool
+check_addr(struct device *dev, dma_addr_t dma_addr, size_t size,
+ const char *caller)
+{
+ if (unlikely(dev && !dma_capable(dev, dma_addr, size))) {
+ if (*dev->dma_mask >= DMA_BIT_MASK(32)) {
+ dev_err(dev,
+ "%s: overflow %pad+%zu of device mask %llx\n",
+ caller, &dma_addr, size, *dev->dma_mask);
+ }
+ return false;
+ }
+ return true;
+}
+
+static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size)
+{
+ return phys_to_dma(dev, phys) + size - 1 <= dev->coherent_dma_mask;
+}
+
+void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
+ gfp_t gfp, unsigned long attrs)
+{
+ unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+ int page_order = get_order(size);
+ struct page *page = NULL;
+
+ /* GFP_DMA32 and GFP_DMA are no ops without the corresponding zones: */
+ if (dev->coherent_dma_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
+ gfp |= GFP_DMA;
+ if (dev->coherent_dma_mask <= DMA_BIT_MASK(32) && !(gfp & GFP_DMA))
+ gfp |= GFP_DMA32;
+
+again:
+ /* CMA can be used only in the context which permits sleeping */
+ if (gfpflags_allow_blocking(gfp)) {
+ page = dma_alloc_from_contiguous(dev, count, page_order, gfp);
+ if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
+ dma_release_from_contiguous(dev, page, count);
+ page = NULL;
+ }
+ }
+ if (!page)
+ page = alloc_pages_node(dev_to_node(dev), gfp, page_order);
+
+ if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
+ __free_pages(page, page_order);
+ page = NULL;
+
+ if (dev->coherent_dma_mask < DMA_BIT_MASK(32) &&
+ !(gfp & GFP_DMA)) {
+ gfp = (gfp & ~GFP_DMA32) | GFP_DMA;
+ goto again;
+ }
+ }
+
+ if (!page)
+ return NULL;
+
+ *dma_handle = phys_to_dma(dev, page_to_phys(page));
+ memset(page_address(page), 0, size);
+ return page_address(page);
+}
+
+void dma_direct_free(struct device *dev, size_t size, void *cpu_addr,
+ dma_addr_t dma_addr, unsigned long attrs)
+{
+ unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+
+ if (!dma_release_from_contiguous(dev, virt_to_page(cpu_addr), count))
+ free_pages((unsigned long)cpu_addr, get_order(size));
+}
+
+static dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
+ unsigned long offset, size_t size, enum dma_data_direction dir,
+ unsigned long attrs)
+{
+ dma_addr_t dma_addr = phys_to_dma(dev, page_to_phys(page)) + offset;
+
+ if (!check_addr(dev, dma_addr, size, __func__))
+ return DIRECT_MAPPING_ERROR;
+ return dma_addr;
+}
+
+static int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl,
+ int nents, enum dma_data_direction dir, unsigned long attrs)
+{
+ int i;
+ struct scatterlist *sg;
+
+ for_each_sg(sgl, sg, nents, i) {
+ BUG_ON(!sg_page(sg));
+
+ sg_dma_address(sg) = phys_to_dma(dev, sg_phys(sg));
+ if (!check_addr(dev, sg_dma_address(sg), sg->length, __func__))
+ return 0;
+ sg_dma_len(sg) = sg->length;
+ }
+
+ return nents;
+}
+
+int dma_direct_supported(struct device *dev, u64 mask)
+{
+#ifdef CONFIG_ZONE_DMA
+ if (mask < DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
+ return 0;
+#else
+ /*
+ * Because 32-bit DMA masks are so common we expect every architecture
+ * to be able to satisfy them - either by not supporting more physical
+ * memory, or by providing a ZONE_DMA32. If neither is the case, the
+ * architecture needs to use an IOMMU instead of the direct mapping.
+ */
+ if (mask < DMA_BIT_MASK(32))
+ return 0;
+#endif
+ return 1;
+}
+
+static int dma_direct_mapping_error(struct device *dev, dma_addr_t dma_addr)
+{
+ return dma_addr == DIRECT_MAPPING_ERROR;
+}
+
+const struct dma_map_ops dma_direct_ops = {
+ .alloc = dma_direct_alloc,
+ .free = dma_direct_free,
+ .map_page = dma_direct_map_page,
+ .map_sg = dma_direct_map_sg,
+ .dma_supported = dma_direct_supported,
+ .mapping_error = dma_direct_mapping_error,
+};
+EXPORT_SYMBOL(dma_direct_ops);