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122c234ef4
Commitba0fb44aed("dma-mapping: replace zone_dma_bits by zone_dma_limit") optimistically assumed that device-tree dma-ranges property describes the system DMA limits. That assumption ignores DMA limits of individual devices that are not encoded in device tree. Commit833bd284a4("arm64: mm: fix DMA zone when dma-ranges is missing") fixed part of the problem for platforms that do not provide dma-ranges at all. However platforms like SM8550-HDK provide DMA bus limit, but have devices with stronger DMA limits. of_dma_get_max_cpu_address() does not take device limitations into account. These platforms implicitly rely on DMA zone in low 32-bit RAM area. Until we find a better way to figure out the optimal DMA zone range, restore the low RAM DMA zone we had before commitba0fb44aed. Fixes:ba0fb44aed("dma-mapping: replace zone_dma_bits by zone_dma_limit") Closes: https://lore.kernel.org/r/1a0c7282-63e0-4add-8e38-3abe3e0a8e2f@linaro.org Reported-by: Neil Armstrong <neil.armstrong@linaro.org> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Suggested-by: Robin Murphy <robin.murphy@arm.com> Signed-off-by: Baruch Siach <baruch@tkos.co.il> Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on SM8550-HDK Tested-by: Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by: Christoph Hellwig <hch@lst.de>
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.