On Thursday 12 November 2015 15:33:41 Phil Edworthy wrote: > On 12 November 2015 09:49, Arnd Bergmann wrote: > > On Thursday 12 November 2015 09:26:33 Phil Edworthy wrote: > > > On 11 November 2015 18:25, LIviu wrote: > > > > On Mon, Nov 09, 2015 at 12:32:13PM +0000, Phil Edworthy wrote: > > > > of_dma_configure calls of_dma_get_range to do all this for the PCIe host, > > and then calls arch_setup_dma_ops() so the architecture specific code can > > enforce the limits in dma_set_mask and pick an appropriate set of dma > > operations. The missing part is in the implementation of arch_setup_dma_ops, > > which currently happily ignores the base and limit. > I don't think it's as simple as that, though I could be wrong! > > First off, of_dma_configure() sets a default coherent_dma_mask to 4GiB. > This default is set for the 'platform soc' device. For my own testing I increased > this to DMA_BIT_MASK(63). Note that setting it to DMA_BIT_MASK(64) causes > boot failure that I haven't looked into. Most platform devices actually need the 32-bit mask, so we intentionally followed what PCI does here and default to that and require platform drivers to explicitly ask for a larger mask if they need it. > Then pci_device_add() sets the devices coherent_dma_mask to 4GiB before > calling of_pci_dma_configure(). I assume it does this on the basis that this is a > good default for PCI drivers that don't call dma_set_mask(). > So if arch_setup_dma_ops() walks up the parents to limit the mask, you'll hit > this mask. arch_setup_dma_ops() does not walk up the hierarchy, of_dma_configure() does this before calling arch_setup_dma_ops(). The PCI devices start out with the 32-bit mask, but the limit should be whatever PCI host uses. > Finally, dma_set_mask_and_coherent() is called from the PCI card driver > but it doesn't check the parents dma masks either. The way I think this should work is that arch_setup_dma_ops() stores the allowed mask in the struct device, and that dma_set_mask compares the mask against that. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
