ich777/linux_media
1
0
Fork 0
mirror of https://github.com/tbsdtv/linux_media.git synced 2025-07-23 12:43:29 +02:00
Code Issues Packages Projects Releases Wiki Activity

dma-mapping: treat dev->bus_dma_mask as a DMA limit

Browse Source 
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>
This commit is contained in:
Nicolas Saenz Julienne
2019-11-21 10:26:44 +01:00
committed by Christoph Hellwig
parent d7293f79ca
commit a7ba70f178
13 changed files with 46 additions and 53 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/dma-direct.h
View File

@@ -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);