Ard, > So before these changes, we were in the exact same situation, but since PC > platforms never enable DMA above 4 GB in the first place, nobody ever > noticed until we started running this code on arm64 platforms that have no > 32-bit addressable DRAM to begin with.
Interesting - I did not realize that there were designs that were crazy enough to have no addressable DRAM below 4G. > The obvious conclusion is that the driver should not set the > EFI_PCI_IO_ATTRIBUTE_DUAL_ADDRESS_CYCLE attribute if the device does > not support it, or, which seems to be our case, if the driver does not > implement the 64-bit DMA mode that the driver does support. However, > since there are platforms for which bounce buffering is not an option (since > there is no 32-bit addressable memory to bounce to), this is not just a > performance optimization, and so it would be useful to fix the code so it can > drive all 64-bit DMA capable hardware. Okay, that's a great reason - let's get V3 64b ADMA2 in! Any objection to committing the original patch in the short term? Thanks, Eugene _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
