diff options
| author | Nicolas Saenz Julienne | 2019-11-21 10:26:44 +0100 |
|---|---|---|
| committer | Christoph Hellwig | 2019-11-21 18:14:35 +0100 |
| commit | a7ba70f1787f977f970cd116076c6fce4b9e01cc (patch) | |
| tree | 474b2c0bc2201b3d2adde4c7887d4f76d50ac753 /drivers/ata | |
| parent | d7293f79caea45c50c0ab4294847e7af96501ced (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.c | 2 |
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; |