On Fri, 1 Mar 2019 at 11:32, Ard Biesheuvel <ard.biesheu...@linaro.org> wrote: > > On Fri, 1 Mar 2019 at 01:19, Ashish Singhal <ashishsin...@nvidia.com> wrote: > > > > Eugene, > > > > Small question. Did the issue appear after the V4 patch went in? Looking at > > the code before that patch, we were enabling 64b dma in pci based on > > capability register already despite of driver supporting only 32b dma. > > > > I think this may have been an oversight on my part when I originally > added the DUAL_ADDRESS_CYCLE handling. > > The following commit added EFI_PCI_ATTRIBUTE_DUAL_ADDRESS_CYCLE to the > host bridge driver > > commit e58a71d9c50ba641b5ab19f5ce2cbf772187de4d > Author: Ard Biesheuvel <ard.biesheu...@linaro.org> > Date: Mon Sep 5 09:55:16 2016 +0100 > > MdeModulePkg/PciHostBridgeDxe: restrict 64-bit DMA to devices that > support it > > Currently, the EFI_PCI_ATTRIBUTE_DUAL_ADDRESS_CYCLE attribute is > completely > ignored by the PCI host bridge driver, which means that, on an > implementation > that supports DMA above 4 GB, allocations above 4 GB may be provided to > devices that have not expressed support for it. > > and the SDHCI driver was fixed accordingly in > > Author: Ard Biesheuvel <ard.biesheu...@linaro.org> > Date: Mon Sep 5 09:51:48 2016 +0100 > > MdeModulePkg/SdMmcPciHcDxe: enable 64-bit PCI DMA > > PCI controller drivers must set the > EFI_PCI_IO_ATTRIBUTE_DUAL_ADDRESS_CYCLE > attribute if the controller supports 64-bit DMA addressing. > > 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. > > 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.
Correction: that the *device* 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. _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
