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The AXI-DMAC supports different types of interface for the data source and destination ports. Typically one of those ports is a memory-mapped interface while the other is some kind of streaming interface. The information about which kind of interface is used for each port is encoded in the devicetree. It is also possible in the driver to detect whether a port supports memory-mapped transfers or not. For streaming interfaces the address register is read-only and will always return 0. So in order to check if a port supports memory-mapped transfers write a non-zero value to the corresponding address register and check that the value read-back is still non zero. This allows to detect mismatches between the devicetree description and the actual hardware configuration. Unfortunately it is not possible to autodetect the interface types since there is no method to distinguish between the different streaming ports. So the best thing that can be done is to error out when a memory mapped port is described in the devicetree but none is detected in the hardware. Signed-off-by: Lars-Peter Clausen <lars@metafoo.de> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com> Signed-off-by: Vinod Koul <vkoul@kernel.org>
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.