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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/ata
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 'drivers/ata')
-rw-r--r--drivers/ata/ahci.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index 05c2b32dcc4d..7c6d06ffb586 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -897,7 +897,7 @@ static int ahci_configure_dma_masks(struct pci_dev *pdev, int using_dac)
* value, don't extend it here. This happens on STA2X11, for example.
*
* XXX: manipulating the DMA mask from platform code is completely
- * bogus, platform code should use dev->bus_dma_mask instead..
+ * bogus, platform code should use dev->bus_dma_limit instead..
*/
if (pdev->dma_mask && pdev->dma_mask < DMA_BIT_MASK(32))
return 0;