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Oleksij Rempel 66e69d8849 ARM: imx6q: remove PHY fixup for KSZ9031 Starting with: `bcf3440c6d` ("net: phy: micrel: add phy-mode support for the KSZ9031 PHY") the micrel phy driver started respecting phy-mode for the KSZ9031 PHY. At least with kernel v5.8 configuration provided by this fixup was overwritten by the micrel driver. This fixup was providing following configuration: RX path: 2.58ns delay rx -0.42 (left shift) + rx_clk +0.96ns (right shift) = 1,38 + 1,2 internal RX delay = 2.58ns TX path: 0.96ns delay tx (no delay) + tx_clk 0.96ns (right shift) = 0.96ns This configuration is outside of the recommended RGMII clock skew delays and about in the middle of: rgmii-idrx and rgmii-id Since most embedded systems do not have enough place to introduce significant clock skew, rgmii-id is the way to go. In case this patch breaks network functionality on your system, build kernel with enabled MICREL_PHY. If it is still not working then try following device tree options: 1. Set (or change) phy-mode in DT to: phy-mode = "rgmii-id"; This actives internal delay for both RX and TX. 1. Set (or change) phy-mode in DT to: phy-mode = "rgmii-idrx"; This actives internal delay for RX only. 3. Use following DT properties: phy-mode = "rgmii"; txen-skew-psec = <0>; rxdv-skew-psec = <0>; rxd0-skew-psec = <0>; rxd1-skew-psec = <0>; rxd2-skew-psec = <0>; rxd3-skew-psec = <0>; rxc-skew-psec = <1860>; txc-skew-psec = <1860>; This activates the internal delays for RX and TX, with the value as the fixup that is removed in this patch. Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de> Reviewed-by: Andrew Lunn <andrew@lunn.ch> Signed-off-by: Shawn Guo <shawnguo@kernel.org>		2021-05-23 11:32:46 +08:00
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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 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.