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authorNicolas Saenz Julienne <nsaenzjulienne@suse.de>2019-11-21 10:26:44 +0100
committerChristoph Hellwig <hch@lst.de>2019-11-21 18:14:35 +0100
commita7ba70f1787f977f970cd116076c6fce4b9e01cc (patch)
tree474b2c0bc2201b3d2adde4c7887d4f76d50ac753 /include/linux
parentd7293f79caea45c50c0ab4294847e7af96501ced (diff)
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')
-rw-r--r--include/linux/device.h6
-rw-r--r--include/linux/dma-direct.h2
-rw-r--r--include/linux/dma-mapping.h2
3 files changed, 5 insertions, 5 deletions
diff --git a/include/linux/device.h b/include/linux/device.h
index 297239a08bb7..e396de656f20 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1186,8 +1186,8 @@ struct dev_links_info {
* @coherent_dma_mask: Like dma_mask, but for alloc_coherent mapping as not all
* hardware supports 64-bit addresses for consistent allocations
* such descriptors.
- * @bus_dma_mask: Mask of an upstream bridge or bus which imposes a smaller DMA
- * limit than the device itself supports.
+ * @bus_dma_limit: Limit of an upstream bridge or bus which imposes a smaller
+ * DMA limit than the device itself supports.
* @dma_pfn_offset: offset of DMA memory range relatively of RAM
* @dma_parms: A low level driver may set these to teach IOMMU code about
* segment limitations.
@@ -1270,7 +1270,7 @@ struct device {
not all hardware supports
64 bit addresses for consistent
allocations such descriptors. */
- u64 bus_dma_mask; /* upstream dma_mask constraint */
+ u64 bus_dma_limit; /* upstream dma constraint */
unsigned long dma_pfn_offset;
struct device_dma_parameters *dma_parms;
diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
index 452f5280cde3..24b8684aa21d 100644
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -63,7 +63,7 @@ static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size,
min(addr, end) < phys_to_dma(dev, PFN_PHYS(min_low_pfn)))
return false;
- return end <= min_not_zero(*dev->dma_mask, dev->bus_dma_mask);
+ return end <= min_not_zero(*dev->dma_mask, dev->bus_dma_limit);
}
u64 dma_direct_get_required_mask(struct device *dev);
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);
}