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Synopsys DesignWare XPCS IP-core can be synthesized with the device CSRs being accessible over the MCI or APB3 interface instead of the MDIO bus (see the CSR_INTERFACE HDL parameter). Thus all the PCS registers can be just memory mapped and be a subject of the standard MMIO operations of course taking into account the peculiarities of the Clause C45 CSRs mapping. From that perspective the DW XPCS devices would look as just normal platform devices for the kernel. On the other hand in order to have the DW XPCS devices handled by the pcs-xpcs.c driver they need to be registered in the framework of the MDIO-subsystem. So the suggested change is about providing a DW XPCS platform device driver registering a virtual MDIO-bus with a single MDIO-device representing the DW XPCS device. DW XPCS platform device is supposed to be described by the respective compatible string "snps,dw-xpcs" (or with the PMA-specific compatible string), CSRs memory space and optional peripheral bus and reference clock sources. Depending on the INDIRECT_ACCESS IP-core synthesize parameter the memory-mapped reg-space can be represented as either directly or indirectly mapped Clause 45 space. In the former case the particular address is determined based on the MMD device and the registers offset (5 + 16 bits all together) within the device reg-space. In the later case there is only 8 lower address bits are utilized for the registers mapping (255 CSRs). The upper bits are supposed to be written into the respective viewport CSR in order to select the respective MMD sub-page. Note, only the peripheral bus clock source is requested in the platform device probe procedure. The core and pad clocks handling has been implemented in the framework of the xpcs_create() method intentionally since the clocks-related setups are supposed to be performed later, during the DW XPCS main configuration procedures. (For instance they will be required for the DW Gen5 10G PMA configuration.) Signed-off-by: Serge Semin <fancer.lancer@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> |
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| README | ||
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.