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authorNicolas Saenz Julienne <nsaenzjulienne@suse.de>2019-11-21 12:26:44 +0300
committerChristoph Hellwig <hch@lst.de>2019-11-21 20:14:35 +0300
commita7ba70f1787f977f970cd116076c6fce4b9e01cc (patch)
tree474b2c0bc2201b3d2adde4c7887d4f76d50ac753 /include/linux/dma-mapping.h
parentd7293f79caea45c50c0ab4294847e7af96501ced (diff)
downloadlinux-a7ba70f1787f977f970cd116076c6fce4b9e01cc.tar.xz
dma-mapping: treat dev->bus_dma_mask as a DMA limit
Using a mask to represent bus DMA constraints has a set of limitations. The biggest one being it can only hold a power of two (minus one). The DMA mapping code is already aware of this and treats dev->bus_dma_mask as a limit. This quirk is already used by some architectures although still rare. With the introduction of the Raspberry Pi 4 we've found a new contender for the use of bus DMA limits, as its PCIe bus can only address the lower 3GB of memory (of a total of 4GB). This is impossible to represent with a mask. To make things worse the device-tree code rounds non power of two bus DMA limits to the next power of two, which is unacceptable in this case. In the light of this, rename dev->bus_dma_mask to dev->bus_dma_limit all over the tree and treat it as such. Note that dev->bus_dma_limit should contain the higher accessible DMA address. Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de> Reviewed-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'include/linux/dma-mapping.h')
-rw-r--r--include/linux/dma-mapping.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 4d450672b7d6..c4d8741264bd 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -697,7 +697,7 @@ static inline int dma_coerce_mask_and_coherent(struct device *dev, u64 mask)
*/
static inline bool dma_addressing_limited(struct device *dev)
{
- return min_not_zero(dma_get_mask(dev), dev->bus_dma_mask) <
+ return min_not_zero(dma_get_mask(dev), dev->bus_dma_limit) <
dma_get_required_mask(dev);
}