similar to: [PATCH] drm/nouveau: tegra: Detach from ARM DMA/IOMMU mapping

From: Thierry Reding <treding at nvidia.com> Depending on the kernel configuration, early ARM architecture setup code may have attached the GPU to a DMA/IOMMU mapping that transparently uses the IOMMU to back the DMA API. Tegra requires special handling for IOMMU backed buffers (a special bit in the GPU's MMU page tables indicates the memory path to take: via the SMMU or directly to the

From: Thierry Reding <treding at nvidia.com> An unfortunate interaction between the 32-bit ARM DMA/IOMMU mapping code and Tegra SMMU driver changes to support IOMMU groups introduced a boot- time regression on Tegra124. This was caught very late because none of the standard configurations that are tested on Tegra enable the ARM DMA/ IOMMU mapping code since it is not needed. The reason for

From: Thierry Reding <treding at nvidia.com> Depending on the kernel configuration, early ARM architecture setup code may have attached the GPU to a DMA/IOMMU mapping that transparently uses the IOMMU to back the DMA API. Tegra requires special handling for IOMMU backed buffers (a special bit in the GPU's MMU page tables indicates the memory path to take: via the SMMU or directly to the

From: Thierry Reding <treding at nvidia.com> An unfortunate interaction between the 32-bit ARM DMA/IOMMU mapping code and Tegra SMMU driver changes to support IOMMU groups introduced a boot- time regression on Tegra124. This was caught very late because none of the standard configurations that are tested on Tegra enable the ARM DMA/ IOMMU mapping code since it is not needed. The reason for

Hi Thierry, On 16/09/2019 16:04, Thierry Reding wrote: > From: Thierry Reding <treding at nvidia.com> > > If the GPU is already attached to an IOMMU, don't detach it and setup an > explicit IOMMU domain. Since Nouveau can now properly handle the case of > the DMA API being backed by an IOMMU, just continue using the DMA API. > > Signed-off-by: Thierry Reding

On 16/09/2019 16:57, Thierry Reding wrote: > On Mon, Sep 16, 2019 at 04:29:18PM +0100, Robin Murphy wrote: >> Hi Thierry, >> >> On 16/09/2019 16:04, Thierry Reding wrote: >>> From: Thierry Reding <treding at nvidia.com> >>> >>> If the GPU is already attached to an IOMMU, don't detach it and setup an >>> explicit IOMMU domain. Since

On Wed, May 30, 2018 at 04:06:24PM +0200, Thierry Reding wrote: > From: Thierry Reding <treding at nvidia.com> > > Instead of setting the DMA ops pointer to NULL, set the correct, > non-IOMMU ops depending on the device's coherency setting. > > Signed-off-by: Thierry Reding <treding at nvidia.com> > --- > Changes in v4: > - new patch to fix existing

> +void arch_iommu_detach_device(struct device *dev) > +{ > +#ifdef CONFIG_ARM_DMA_USE_IOMMU > + struct dma_iommu_mapping *mapping = to_dma_iommu_mapping(dev); > + const struct dma_map_ops *dma_ops; > + > + if (!mapping) > + return; > + > + arm_iommu_release_mapping(mapping); > + arm_iommu_detach_device(dev); > + > + dma_ops =

On 30/05/18 09:03, Thierry Reding wrote: > From: Thierry Reding <treding at nvidia.com> > > Implement this function to enable drivers from detaching from any IOMMU > domains that architecture code might have attached them to so that they > can take exclusive control of the IOMMU via the IOMMU API. > > Signed-off-by: Thierry Reding <treding at nvidia.com> > ---

From: Thierry Reding <treding at nvidia.com> Depending on the kernel configuration, early ARM architecture setup code may have attached the GPU to a DMA/IOMMU mapping that transparently uses the IOMMU to back the DMA API. Tegra requires special handling for IOMMU backed buffers (a special bit in the GPU's MMU page tables indicates the memory path to take: via the SMMU or directly to the

From: Thierry Reding <treding at nvidia.com> The ARM_DMA_USE_IOMMU Kconfig option has side-effects that drivers can not opt into but have to explicitly opt out of. This can lead to subtle bugs that are difficult to track down and not immediately obvious to be related to this Kconfig option. To avoid this confusion, always enable the option to expose any lurking bugs once and allow any

On 30/05/18 14:00, Thierry Reding wrote: > On Wed, May 30, 2018 at 11:30:25AM +0100, Robin Murphy wrote: >> On 30/05/18 09:03, Thierry Reding wrote: >>> From: Thierry Reding <treding at nvidia.com> >>> >>> Depending on the kernel configuration, early ARM architecture setup code >>> may have attached the GPU to a DMA/IOMMU mapping that

On 30/05/18 09:03, Thierry Reding wrote: > From: Thierry Reding <treding at nvidia.com> > > Depending on the kernel configuration, early ARM architecture setup code > may have attached the GPU to a DMA/IOMMU mapping that transparently uses > the IOMMU to back the DMA API. Tegra requires special handling for IOMMU > backed buffers (a special bit in the GPU's MMU page

From: Thierry Reding <treding at nvidia.com> Instead of setting the DMA ops pointer to NULL, set the correct, non-IOMMU ops depending on the device's coherency setting. Signed-off-by: Thierry Reding <treding at nvidia.com> --- Changes in v4: - new patch to fix existing arm_iommu_detach_device() to do what we need arch/arm/mm/dma-mapping.c | 12 ++++++------ 1 file changed, 6

From: Thierry Reding <treding at nvidia.com> If the GPU is already attached to an IOMMU, don't detach it and setup an explicit IOMMU domain. Since Nouveau can now properly handle the case of the DMA API being backed by an IOMMU, just continue using the DMA API. Signed-off-by: Thierry Reding <treding at nvidia.com> --- .../drm/nouveau/nvkm/engine/device/tegra.c | 19

On Mon, Sep 16, 2019 at 04:29:18PM +0100, Robin Murphy wrote: > Hi Thierry, > > On 16/09/2019 16:04, Thierry Reding wrote: > > From: Thierry Reding <treding at nvidia.com> > > > > If the GPU is already attached to an IOMMU, don't detach it and setup an > > explicit IOMMU domain. Since Nouveau can now properly handle the case of > > the DMA API

Hello, There is a trouble on ARM with DMA allocations made by device drivers, the trouble is that DMA allocations are getting implicitly backed with IOMMU mapping by the driver core if IOMMU presents in a system and IOMMU could handle device. This is an undesired behaviour for drivers that manage IOMMU by themselves, like NVIDIA Tegra GPU driver. On arm32 the implicit backing happens if

On Wed, May 30, 2018 at 10:59:30AM +0100, Robin Murphy wrote: > On 30/05/18 09:03, Thierry Reding wrote: > > From: Thierry Reding <treding at nvidia.com> > > > > Implement this function to enable drivers from detaching from any IOMMU > > domains that architecture code might have attached them to so that they > > can take exclusive control of the IOMMU via

On Wed, Apr 25, 2018 at 08:20:49AM -0700, Christoph Hellwig wrote: > > +void arch_iommu_detach_device(struct device *dev) > > +{ > > +#ifdef CONFIG_ARM_DMA_USE_IOMMU > > + struct dma_iommu_mapping *mapping = to_dma_iommu_mapping(dev); > > + const struct dma_map_ops *dma_ops; > > + > > + if (!mapping) > > + return; > > + > > +

From: Thierry Reding <treding at nvidia.com> Implement this function to enable drivers from detaching from any IOMMU domains that architecture code might have attached them to so that they can take exclusive control of the IOMMU via the IOMMU API. Signed-off-by: Thierry Reding <treding at nvidia.com> --- arch/arm/include/asm/dma-mapping.h | 3 +++ arch/arm/mm/dma-mapping-nommu.c