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For PCI, the second and third cell in ranges specifies the upper and lower target address for address translation. This target address will be used to program the internal address translation unit (iATU). The current device tree configuration will program the iATU to translate CPU accesses to 0x08000000 to PCI address 0x0 (with TLP type MEM). The device tree configuration also specifies that CPU acesses to 0x0fe00000 will be translated to PCI address 0x0 (with TLP type I/O). We cannot have both I/O space and memory space at PCI address 0x0. The PCI code already uses the CPU address when assigning addresses to memory BARs, so for memory space the PCI address should be the same as the CPU address. This also matches how all other device trees using snps,dw-pcie are configured. The existing configuration appears to work, even if it is incorrect. For some reason the iATU doesn't obey the existing configuration, and doesn't translate CPU accesses from 0x08000000 to PCI address 0x0. The reason why the existing configuration works at all is probably because the default behavior, when there is no match, is to use the untranslated address. This happens to work for memory space, since it's a 1:1 mapping. However, instead of relying on this behavior, let's configure the iATU correctly. Signed-off-by: Niklas Cassel <niklas.cassel@linaro.org> Signed-off-by: Andy Gross <andy.gross@linaro.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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.