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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 /drivers/of
parentMerge branch 'for-next/zone-dma' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux into dma-mapping-for-next (diff)
downloadlinux-dev-a7ba70f1787f977f970cd116076c6fce4b9e01cc.tar.xz
linux-dev-a7ba70f1787f977f970cd116076c6fce4b9e01cc.zip
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 'drivers/of')
-rw-r--r--drivers/of/device.c9
1 files changed, 5 insertions, 4 deletions
diff --git a/drivers/of/device.c b/drivers/of/device.c
index da8158392010..e9127db7b067 100644
--- a/drivers/of/device.c
+++ b/drivers/of/device.c
@@ -93,7 +93,7 @@ int of_dma_configure(struct device *dev, struct device_node *np, bool force_dma)
bool coherent;
unsigned long offset;
const struct iommu_ops *iommu;
- u64 mask;
+ u64 mask, end;
ret = of_dma_get_range(np, &dma_addr, &paddr, &size);
if (ret < 0) {
@@ -148,12 +148,13 @@ int of_dma_configure(struct device *dev, struct device_node *np, bool force_dma)
* Limit coherent and dma mask based on size and default mask
* set by the driver.
*/
- mask = DMA_BIT_MASK(ilog2(dma_addr + size - 1) + 1);
+ end = dma_addr + size - 1;
+ mask = DMA_BIT_MASK(ilog2(end) + 1);
dev->coherent_dma_mask &= mask;
*dev->dma_mask &= mask;
- /* ...but only set bus mask if we found valid dma-ranges earlier */
+ /* ...but only set bus limit if we found valid dma-ranges earlier */
if (!ret)
- dev->bus_dma_mask = mask;
+ dev->bus_dma_limit = end;
coherent = of_dma_is_coherent(np);
dev_dbg(dev, "device is%sdma coherent\n",