On 15/04/16 19:29, Timur Tabi wrote:
On Thu, Apr 14, 2016 at 12:25 PM, Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> 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@xxxxxxxxxxxxxxx/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.
In your patches, where is coherent_dma_mask initialized? I found this code in add_smmu_platform_device(), but I think this is setting the mask for the IOMMU driver, not the individual devices.
Yes, that's for the SMMU itself as a device (i.e. the page table walker) - as a handy example of "drivers which actually care about DMA masks", it specifically needs to avoid a too-small DMA mask because bounce-buffering the page tables tends to make things go horribly wrong.
Robin.
Either way, I don't understand where the correct value is going to be overridden. + /* + * Set default dma mask value for the table walker, + * to be overridden on probing with correct value. + */ + *pdev->dev.dma_mask = DMA_BIT_MASK(32); + pdev->dev.coherent_dma_mask = *pdev->dev.dma_mask;
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