On Fri, Jan 16, 2015 at 03:14:13PM +0000, Arnd Bergmann wrote: > On Friday 16 January 2015 14:55:45 Will Deacon wrote: > > On Fri, Jan 16, 2015 at 02:45:30PM +0000, Tom Lendacky wrote: > > > I have tested ACPI-enablement patches for the amd-xgbe/amd-xgbe-phy > > > drivers that I'm about to submit upstream with the V7 patch series > > > on the AMD Seattle server platform. There does not appear to be support > > > for the _CCA attribute in this patch series. The amd-xgbe driver will > > > setup the device domain and cache attributes based on the presence of > > > this attribute, but it requires the arch support to assign the proper > > > DMA operations in order for it to all work correctly. > > > > > > Overriding the _CCA attribute in the driver, I was able to successfully > > > test the driver and this patch series. > > > > Hopefully this will all be addressed when the IORT parts of ACPI have > > settled down (the current proposal allows for these attributes to be > > described as well as their interaction with things like IOMMUs). > > > > In the meantime, are you falling back to non-coherent DMA? If so, what > > attributes have you settled on? We need to be really careful not to > > corrupt data during cache invalidatation when mapping a non-coherent > > buffer for the CPU. > > I think in case of ACPI we should use cache-coherent as the default, > as this is what all servers will use for DMA masters. Last time I heard in some call, it was agreed that _CCA properties should always be present and Linux should not make any assumption (there is no safe assumption here). While better options may appear in ACPI, _CCA is what we currently have. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
