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When running Xen on iMX8QXP, an Arm SoC without IOMMU, DMA performed via its eDMA v3 DMA engine fail with a mapping error. The eDMA performs DMA between RAM and MMIO space, and it's the MMIO side that cannot be mapped. MMIO->RAM DMA access cannot be bounce buffered if it would straddle a page boundary and on Xen the MMIO space is 1:1 mapped for Arm, and x86 PV Dom0. Cases where MMIO space is not 1:1 mapped, such as x86 PVH Dom0, requires an IOMMU present to deal with the mapping. Considering the above the map_resource callback can just be wired to the existing dma_direct_map_resource() function. There is nothing to do for unmap so the unmap callback is not needed. Signed-off-by: John Ernberg <john.ernberg@actia.se> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org> Message-ID: <20250512071440.3726697-1-john.ernberg@actia.se> Signed-off-by: Juergen Gross <jgross@suse.com>
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 reStructuredText 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.