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 --- arch/powerpc/sysdev/fsl_pci.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'arch/powerpc/sysdev/fsl_pci.c') diff --git a/arch/powerpc/sysdev/fsl_pci.c b/arch/powerpc/sysdev/fsl_pci.c index ff0e2b156cb5..617a443d673d 100644 --- a/arch/powerpc/sysdev/fsl_pci.c +++ b/arch/powerpc/sysdev/fsl_pci.c @@ -115,8 +115,8 @@ static void pci_dma_dev_setup_swiotlb(struct pci_dev *pdev) { struct pci_controller *hose = pci_bus_to_host(pdev->bus); - pdev->dev.bus_dma_mask = - hose->dma_window_base_cur + hose->dma_window_size; + pdev->dev.bus_dma_limit = + hose->dma_window_base_cur + hose->dma_window_size - 1; } static void setup_swiotlb_ops(struct pci_controller *hose) @@ -135,7 +135,7 @@ static void fsl_pci_dma_set_mask(struct device *dev, u64 dma_mask) * mapping that allows addressing any RAM address from across PCI. */ if (dev_is_pci(dev) && dma_mask >= pci64_dma_offset * 2 - 1) { - dev->bus_dma_mask = 0; + dev->bus_dma_limit = 0; dev->archdata.dma_offset = pci64_dma_offset; } } -- cgit v1.2.3