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c61e963734
This allows to dip into zones for lower memory if they are available. If one of the zones is not available the corresponding GFP_* flag will evaluate to 0 so they won't change anything. We provide an arch tunable for those architectures that do not use GFP_DMA for the lowest 24-bits, given that there are a few. Roughly based on the x86 code. Signed-off-by: Christoph Hellwig <hch@lst.de>
115 lines
3.1 KiB
C
115 lines
3.1 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* DMA operations that map physical memory directly without using an IOMMU or
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* flushing caches.
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*/
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#include <linux/export.h>
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#include <linux/mm.h>
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#include <linux/dma-direct.h>
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#include <linux/scatterlist.h>
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#include <linux/dma-contiguous.h>
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#include <linux/pfn.h>
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#define DIRECT_MAPPING_ERROR 0
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/*
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* Most architectures use ZONE_DMA for the first 16 Megabytes, but
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* some use it for entirely different regions:
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*/
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#ifndef ARCH_ZONE_DMA_BITS
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#define ARCH_ZONE_DMA_BITS 24
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#endif
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static bool
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check_addr(struct device *dev, dma_addr_t dma_addr, size_t size,
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const char *caller)
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{
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if (unlikely(dev && !dma_capable(dev, dma_addr, size))) {
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if (*dev->dma_mask >= DMA_BIT_MASK(32)) {
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dev_err(dev,
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"%s: overflow %pad+%zu of device mask %llx\n",
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caller, &dma_addr, size, *dev->dma_mask);
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}
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return false;
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}
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return true;
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}
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static void *dma_direct_alloc(struct device *dev, size_t size,
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dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs)
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{
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unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
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int page_order = get_order(size);
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struct page *page = NULL;
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/* GFP_DMA32 and GFP_DMA are no ops without the corresponding zones: */
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if (dev->coherent_dma_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
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gfp |= GFP_DMA;
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if (dev->coherent_dma_mask <= DMA_BIT_MASK(32) && !(gfp & GFP_DMA))
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gfp |= GFP_DMA32;
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/* CMA can be used only in the context which permits sleeping */
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if (gfpflags_allow_blocking(gfp))
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page = dma_alloc_from_contiguous(dev, count, page_order, gfp);
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if (!page)
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page = alloc_pages_node(dev_to_node(dev), gfp, page_order);
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if (!page)
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return NULL;
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*dma_handle = phys_to_dma(dev, page_to_phys(page));
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memset(page_address(page), 0, size);
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return page_address(page);
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}
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static void dma_direct_free(struct device *dev, size_t size, void *cpu_addr,
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dma_addr_t dma_addr, unsigned long attrs)
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{
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unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
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if (!dma_release_from_contiguous(dev, virt_to_page(cpu_addr), count))
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free_pages((unsigned long)cpu_addr, get_order(size));
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}
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static dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
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unsigned long offset, size_t size, enum dma_data_direction dir,
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unsigned long attrs)
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{
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dma_addr_t dma_addr = phys_to_dma(dev, page_to_phys(page)) + offset;
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if (!check_addr(dev, dma_addr, size, __func__))
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return DIRECT_MAPPING_ERROR;
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return dma_addr;
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}
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static int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl,
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int nents, enum dma_data_direction dir, unsigned long attrs)
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{
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int i;
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struct scatterlist *sg;
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for_each_sg(sgl, sg, nents, i) {
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BUG_ON(!sg_page(sg));
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sg_dma_address(sg) = phys_to_dma(dev, sg_phys(sg));
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if (!check_addr(dev, sg_dma_address(sg), sg->length, __func__))
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return 0;
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sg_dma_len(sg) = sg->length;
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}
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return nents;
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}
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static int dma_direct_mapping_error(struct device *dev, dma_addr_t dma_addr)
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{
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return dma_addr == DIRECT_MAPPING_ERROR;
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}
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const struct dma_map_ops dma_direct_ops = {
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.alloc = dma_direct_alloc,
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.free = dma_direct_free,
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.map_page = dma_direct_map_page,
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.map_sg = dma_direct_map_sg,
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.mapping_error = dma_direct_mapping_error,
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};
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EXPORT_SYMBOL(dma_direct_ops);
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