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 /include | |
| 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 'include')
| -rw-r--r-- | include/linux/device.h | 6 | ||||
| -rw-r--r-- | include/linux/dma-direct.h | 2 | ||||
| -rw-r--r-- | include/linux/dma-mapping.h | 2 |
3 files changed, 5 insertions, 5 deletions
diff --git a/include/linux/device.h b/include/linux/device.h index 297239a08bb7..e396de656f20 100644 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -1186,8 +1186,8 @@ struct dev_links_info { * @coherent_dma_mask: Like dma_mask, but for alloc_coherent mapping as not all * hardware supports 64-bit addresses for consistent allocations * such descriptors. - * @bus_dma_mask: Mask of an upstream bridge or bus which imposes a smaller DMA - * limit than the device itself supports. + * @bus_dma_limit: Limit of an upstream bridge or bus which imposes a smaller + * DMA limit than the device itself supports. * @dma_pfn_offset: offset of DMA memory range relatively of RAM * @dma_parms: A low level driver may set these to teach IOMMU code about * segment limitations. @@ -1270,7 +1270,7 @@ struct device { not all hardware supports 64 bit addresses for consistent allocations such descriptors. */ - u64 bus_dma_mask; /* upstream dma_mask constraint */ + u64 bus_dma_limit; /* upstream dma constraint */ unsigned long dma_pfn_offset; struct device_dma_parameters *dma_parms; diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h index 452f5280cde3..24b8684aa21d 100644 --- a/include/linux/dma-direct.h +++ b/include/linux/dma-direct.h @@ -63,7 +63,7 @@ static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size, min(addr, end) < phys_to_dma(dev, PFN_PHYS(min_low_pfn))) return false; - return end <= min_not_zero(*dev->dma_mask, dev->bus_dma_mask); + return end <= min_not_zero(*dev->dma_mask, dev->bus_dma_limit); } u64 dma_direct_get_required_mask(struct device *dev); diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index 4d450672b7d6..c4d8741264bd 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -697,7 +697,7 @@ static inline int dma_coerce_mask_and_coherent(struct device *dev, u64 mask) */ static inline bool dma_addressing_limited(struct device *dev) { - return min_not_zero(dma_get_mask(dev), dev->bus_dma_mask) < + return min_not_zero(dma_get_mask(dev), dev->bus_dma_limit) < dma_get_required_mask(dev); } |