diff options
| author | Nicolas Saenz Julienne <nsaenzjulienne@suse.de> | 2019-11-21 10:26:44 +0100 |
|---|---|---|
| committer | Christoph Hellwig <hch@lst.de> | 2019-11-21 18:14:35 +0100 |
| commit | a7ba70f1787f977f970cd116076c6fce4b9e01cc (patch) | |
| tree | 474b2c0bc2201b3d2adde4c7887d4f76d50ac753 /drivers/of | |
| 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/of')
| -rw-r--r-- | drivers/of/device.c | 9 |
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", |