On Wed, Aug 23, 2023 at 01:47:23PM -0300, Jason Gunthorpe wrote: > Even though dma-iommu.c and CONFIG_ARM_DMA_USE_IOMMU do approximately the > same stuff, the way they relate to the IOMMU core is quiet different. > > dma-iommu.c expects the core code to setup an UNMANAGED domain (of type > IOMMU_DOMAIN_DMA) and then configures itself to use that domain. This > becomes the default_domain for the group. > > ARM_DMA_USE_IOMMU does not use the default_domain, instead it directly > allocates an UNMANAGED domain and operates it just like an external > driver. In this case group->default_domain is NULL. > > If the driver provides a global static identity_domain then automatically > use it as the default_domain when in ARM_DMA_USE_IOMMU mode. > > This allows drivers that implemented default_domain == NULL as an IDENTITY > translation to trivially get a properly labeled non-NULL default_domain on > ARM32 configs. > > With this arrangment when ARM_DMA_USE_IOMMU wants to disconnect from the > device the normal detach_domain flow will restore the IDENTITY domain as > the default domain. Overall this makes attach_dev() of the IDENTITY domain > called in the same places as detach_dev(). > > This effectively migrates these drivers to default_domain mode. For > drivers that support ARM64 they will gain support for the IDENTITY > translation mode for the dma_api and behave in a uniform way. > > Drivers use this by setting ops->identity_domain to a static singleton > iommu_domain that implements the identity attach. If the core detects > ARM_DMA_USE_IOMMU mode then it automatically attaches the IDENTITY domain > during probe. > > Drivers can continue to prevent the use of DMA translation by returning > IOMMU_DOMAIN_IDENTITY from def_domain_type, this will completely prevent > IOMMU_DMA from running but will not impact ARM_DMA_USE_IOMMU. > > This allows removing the set_platform_dma_ops() from every remaining > driver. > > Remove the set_platform_dma_ops from rockchip and mkt_v1 as all it does > is set an existing global static identity domain. mkt_v1 does not support > IOMMU_DOMAIN_DMA and it does not compile on ARM64 so this transformation > is safe. > > Tested-by: Steven Price <steven.price@xxxxxxx> > Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> > Tested-by: Nicolin Chen <nicolinc@xxxxxxxxxx> > Reviewed-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> > Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx> > --- > drivers/iommu/iommu.c | 21 ++++++++++++++++++++- > drivers/iommu/mtk_iommu_v1.c | 12 ------------ > drivers/iommu/rockchip-iommu.c | 10 ---------- > 3 files changed, 20 insertions(+), 23 deletions(-) > Reviewed-by: Jerry Snitselaar <jsnitsel@xxxxxxxxxx>
