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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@arm.com> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com> Tested-by: Nicolin Chen <nicolinc@nvidia.com> Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com> Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com> Link: https://lore.kernel.org/r/9-v8-81230027b2fa+9d-iommu_all_defdom_jgg@nvidia.com Signed-off-by: Joerg Roedel <jroedel@suse.de> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.