Messages in this thread | | | Subject | Re: [RFC PATCH 09/11] drivers: acpi: implement acpi_dma_configure | From | Tomasz Nowicki <> | Date | Mon, 16 May 2016 17:15:34 +0200 |
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On 18.04.2016 12:43, Robin Murphy wrote: > On 15/04/16 19:29, Timur Tabi wrote: >> On Thu, Apr 14, 2016 at 12:25 PM, Lorenzo Pieralisi >> <lorenzo.pieralisi@arm.com> wrote: >>> +void acpi_dma_configure(struct device *dev, enum dev_dma_attr attr) >>> +{ >>> + struct iommu_ops *iommu; >>> + >>> + iommu = iort_iommu_configure(dev); >>> + >>> + /* >>> + * Assume dma valid range starts at 0 and covers the whole >>> + * coherent_dma_mask. >>> + */ >>> + arch_setup_dma_ops(dev, 0, dev->coherent_dma_mask + 1, iommu, >>> + attr == DEV_DMA_COHERENT); >>> +} >> >> I have a network driver that is impacted by this code, so thank you >> for posting this. (See >> https://www.mail-archive.com/netdev@vger.kernel.org/msg106249.html). >> >> One one SOC, the driver needs to set the mask to 32 bits. On another >> SOC, it needs to set it to 64 bits. On device tree, the driver will >> use dma-ranges. > > That's the wrong way to look at it - the driver isn't _using_ > dma-ranges, you're merely relying on the OF code setting the _default_ > DMA mask differently based on the property. If your driver is in the > minority of those which actually care about DMA masks, then it should be > calling dma_set_mask_and_coherent() appropriately and not relying on the > default.
I don't see the clear strategy for setting DMA mask as well.
Lets consider DT boot method example: 1. SMMUv2 supports 48bit translation and 1:1 address map dma-ranges = <0x0 0x0 0x0 0x0 0x00010000 0x0>; and we are adding PCI device:
pci_device_add -> DMA_BIT_MASK(32) by default pci_dma_configure of_dma_configure -> reads dma-ranges and calculates 48bit DMA mask, but it picks minimum, we stay with DMA_BIT_MASK(32)
now PCI dev turns out to be e1000e NIC: e1000_probe dma_set_mask_and_coherent -> tries to set DMA_BIT_MASK(64) dma_set_mask -> there is no set_dma_mask ops for SMMUv2 so we let it be DMA_BIT_MASK(64). From that point on, we let to use memory which SMMUv2 cannot work with.
Does lack of set_dma_mask is the only missing thing here?
Thanks, Tomasz
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