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The Rockchip PCIe endpoint controller handles PCIe transfers addresses by masking the lower bits of the programmed PCI address and using the same number of lower bits from the CPU address space used for the mapping. For a PCI mapping of size bytes starting from pci_addr, the number of bits masked is the number of address bits changing in the address range [pci_addr..pci_addr + size - 1], up to 20 bits, that is, up to 1MB mappings. This means that when preparing a PCI address mapping, an endpoint function driver must use an offset into the allocated controller memory region that is equal to the mask of the starting PCI address over rockchip_pcie_ep_ob_atu_num_bits() bits. This offset also determines the maximum size of the mapping given the starting PCI address and the fixed 1MB controller memory window size. Implement the ->align_addr() endpoint controller operation to allow the mapping alignment to be transparently handled by endpoint function drivers through the function pci_epc_mem_map(). Link: https://lore.kernel.org/r/20241017015849.190271-6-dlemoal@kernel.org Co-developed-by: Rick Wertenbroek <rick.wertenbroek@gmail.com> Signed-off-by: Rick Wertenbroek <rick.wertenbroek@gmail.com> Signed-off-by: Damien Le Moal <dlemoal@kernel.org> [kwilczynski: change local variable name for address offset] Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org> Signed-off-by: Bjorn Helgaas <bhelgaas@google.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.