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author | Nicolas Saenz Julienne <nsaenzjulienne@suse.de> | 2019-11-21 10:26:44 +0100 |
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committer | Christoph Hellwig <hch@lst.de> | 2019-11-21 18:14:35 +0100 |
commit | a7ba70f1787f977f970cd116076c6fce4b9e01cc (patch) | |
tree | 474b2c0bc2201b3d2adde4c7887d4f76d50ac753 /arch/x86/kernel/pci-dma.c | |
parent | d7293f79caea45c50c0ab4294847e7af96501ced (diff) | |
download | linux-stable-a7ba70f1787f977f970cd116076c6fce4b9e01cc.tar.gz linux-stable-a7ba70f1787f977f970cd116076c6fce4b9e01cc.tar.bz2 linux-stable-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 'arch/x86/kernel/pci-dma.c')
-rw-r--r-- | arch/x86/kernel/pci-dma.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c index fa4352dce491..3a75d665d43c 100644 --- a/arch/x86/kernel/pci-dma.c +++ b/arch/x86/kernel/pci-dma.c @@ -146,7 +146,7 @@ rootfs_initcall(pci_iommu_init); static int via_no_dac_cb(struct pci_dev *pdev, void *data) { - pdev->dev.bus_dma_mask = DMA_BIT_MASK(32); + pdev->dev.bus_dma_limit = DMA_BIT_MASK(32); return 0; } |