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9308c47640
Configure the PRG_ETH0_ADJ_* bits to enable or disable the RX delay based on the various RGMII PHY modes. For now the only supported RX delay settings are: - disabled, use for example for phy-mode "rgmii-id" - 0ns - this is treated identical to "disabled", used for example on boards where the PHY provides 2ns TX delay and the PCB trace length already adds 2ns RX delay - 2ns - for whenever the PHY cannot add the RX delay and the traces on the PCB don't add any RX delay Disabling the RX delay (in case u-boot enables it, which is the case for example on Meson8b Odroid-C1) simply means that PRG_ETH0_ADJ_ENABLE, PRG_ETH0_ADJ_SETUP, PRG_ETH0_ADJ_DELAY and PRG_ETH0_ADJ_SKEW should be disabled (just disabling PRG_ETH0_ADJ_ENABLE may be enough, since that disables the whole re-timing logic - but I find it makes more sense to clear the other bits as well since they depend on that setting). u-boot on Odroid-C1 uses the following steps to enable a 2ns RX delay: - enabling enabling the timing adjustment clock - enabling the timing adjustment logic by setting PRG_ETH0_ADJ_ENABLE - setting the PRG_ETH0_ADJ_SETUP bit The documentation for the PRG_ETH0_ADJ_DELAY and PRG_ETH0_ADJ_SKEW registers indicates that we can even set different RX delays. However, I could not find out how this works exactly, so for now we only support a 2ns RX delay using the exact same way that Odroid-C1's u-boot does. Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com> Signed-off-by: David S. Miller <davem@davemloft.net> |
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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.