Hi Rob, >-----Original Message----- >From: linux-arm-kernel [mailto:linux-arm-kernel-boun...@lists.infradead.org] >On Behalf Of Rob Clark >Sent: Thursday, February 02, 2017 8:33 PM >To: Joerg Roedel <j...@8bytes.org> >Cc: Will Deacon <will.dea...@arm.com>; iommu@lists.linux-foundation.org; >Sricharan <sricha...@codeaurora.org>; linux-arm- >ker...@lists.infradead.org >Subject: Re: [PATCH 0/5] Implement SMMU passthrough using the default domain > >On Thu, Jan 26, 2017 at 12:18 PM, Joerg Roedel <j...@8bytes.org> wrote: >> On Tue, Jan 24, 2017 at 08:42:23PM +0530, Sricharan wrote: >>> Thanks for this series. We had a case with the GPU. >>> The GPU's iommu was setup by kernel and the GPU >>> also does dynamic updates for on-the-fly switching between >>> process pagetables. GPU driver was not using DMA domain and >>> the GPU's firmware was always expecting to run out of contextbank >>> '0' (although not correct) , which was not the case after the DMA domain >>> was made default as '0' was getting allocated for DMA domain and >>> there were concerns about reusing the DMA domain as well. >>> Now with this series, looks there is an way out of that that can be tried. >>> >>> So should the default domain not be per device specific selectable ? >> >> Note that iommu-drivers can request direct-mapping for any given device >> on its initializtion. This is used on x86 for devices that need a 1-1 >> mapping for some reason. >> >> Also device drivers can use the iommu-api and assign their own domain to >> a device, which allows them to manage the dma address space on their >> own. > >Part of the problem is that dev->archdata.dma_ops gets wired up to >iommu_dma_ops. Which isn't so bad on it's own, except that cache ops >are not exposed to drivers, forcing us to use dma-mapping API >(dma_map_sg, etc) for cache operations. > >Possibly we should just expose cache op's to drivers bypass this abuse >of dma-mapping. > [1], with this, when the default domain in not DOMAIN_DMA, then dev->archdata.dma_ops is not set to iommu_dma_ops , instead remains to be swiotlb_ops. Is that not correct for gpu's unmanaged domain case ?
https://www.spinics.net/lists/arm-kernel/msg556209.html >btw, Will, we definitely want this to *not* rely on kcmdline for the >gpu with it's own private iommu case.. Ya, that changes behavior for all devices and some might want DMA_DOMAIN and some UNMANAGED. Regards, Sricharan > >BR, >-R > >_______________________________________________ >linux-arm-kernel mailing list >linux-arm-ker...@lists.infradead.org >http://lists.infradead.org/mailman/listinfo/linux-arm-kernel _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
