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authorJohn Garry <john.garry@huawei.com>2022-07-14 19:15:24 +0800
committerChristoph Hellwig <hch@lst.de>2022-07-19 06:05:41 +0200
commita229cc14f3395311b899e5e582b71efa8dd01df0 (patch)
treec582777858d9da5c8d70cad910a04859b213fd8f /kernel
parent942a8186eb4451700dadd1d60a2e43ce67605991 (diff)
dma-mapping: add dma_opt_mapping_size()
Streaming DMA mapping involving an IOMMU may be much slower for larger total mapping size. This is because every IOMMU DMA mapping requires an IOVA to be allocated and freed. IOVA sizes above a certain limit are not cached, which can have a big impact on DMA mapping performance. Provide an API for device drivers to know this "optimal" limit, such that they may try to produce mapping which don't exceed it. Signed-off-by: John Garry <john.garry@huawei.com> Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com> Acked-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/dma/mapping.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index db7244291b74..1bfe11b1edb6 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -773,6 +773,18 @@ size_t dma_max_mapping_size(struct device *dev)
}
EXPORT_SYMBOL_GPL(dma_max_mapping_size);
+size_t dma_opt_mapping_size(struct device *dev)
+{
+ const struct dma_map_ops *ops = get_dma_ops(dev);
+ size_t size = SIZE_MAX;
+
+ if (ops && ops->opt_mapping_size)
+ size = ops->opt_mapping_size();
+
+ return min(dma_max_mapping_size(dev), size);
+}
+EXPORT_SYMBOL_GPL(dma_opt_mapping_size);
+
bool dma_need_sync(struct device *dev, dma_addr_t dma_addr)
{
const struct dma_map_ops *ops = get_dma_ops(dev);