From a7ba70f1787f977f970cd116076c6fce4b9e01cc Mon Sep 17 00:00:00 2001 From: Nicolas Saenz Julienne Date: Thu, 21 Nov 2019 10:26:44 +0100 Subject: 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 Reviewed-by: Robin Murphy Signed-off-by: Christoph Hellwig --- include/linux/dma-direct.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux/dma-direct.h') 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); -- cgit v1.2.3