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The quad port PHYs (AQR4*) have 4 system interfaces, and some of them,
like AQR412C, can be used with a special firmware provisioning which
multiplexes all ports over a single host-side SerDes lane. The protocol
used over this lane is Cisco 10G-QXGMII feature, or "MUSX", as Aquantia
seems to call it.
One such example is the AQR412C PHY from the NXP SPF-30841 10G-QXGMII
add-in card, which uses this firmware file:
https://github.com/nxp-qoriq/qoriq-firmware-aquantia/blob/master/AQR-G3_v4.3.C-AQR_NXP_SPF-30841_MUSX_ID40019_VER1198.cld
There seems to be no disagreement, including from Marvell FAE, that
10G-QXGMII is reported to the host over MDIO as USXGMII and
indistinguishable from it. This includes the registers from the
provisioning based on which the firmware configures a single system
interface (lane C in the case of SPF-30841) to multiplex all ports -
they are also only accessible from the firmware, or over I2C (?!).
However, the Linux MAC and especially SerDes drivers may need to know if
it is using 1 port per lane (USXGMII) or 4 ports per lane (10G-QXGMII).
In the downstream Layerscape SDK we have previously implemented a
simpler scheme where for certain PHY interface modes, we trust the
device tree and never let the PHY driver overwrite phydev->interface:
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .pylintrc | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| 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.