Documentation/networking/sfp-phylink.rst - linux - Git at Google

 .. SPDX-License-Identifier: GPL-2.0

 =======
 phylink
 =======

 Overview
 ========

 phylink is a mechanism to support hot-pluggable networking modules
 without needing to re-initialise the adapter on hot-plug events.

 phylink supports conventional phylib-based setups, fixed link setups
 and SFP (Small Formfactor Pluggable) modules at present.

 Modes of operation
 ==================

 phylink has several modes of operation, which depend on the firmware
 settings.

 1. PHY mode

    In PHY mode, we use phylib to read the current link settings from
    the PHY, and pass them to the MAC driver.  We expect the MAC driver
    to configure exactly the modes that are specified without any
    negotiation being enabled on the link.

 2. Fixed mode

    Fixed mode is the same as PHY mode as far as the MAC driver is
    concerned.

 3. In-band mode

    In-band mode is used with 802.3z, SGMII and similar interface modes,
    and we are expecting to use and honor the in-band negotiation or
    control word sent across the serdes channel.

 By example, what this means is that:

 .. code-block:: none

   &eth {
     phy = <&phy>;
     phy-mode = "sgmii";
   };

 does not use in-band SGMII signalling.  The PHY is expected to follow
 exactly the settings given to it in its :c:func:`mac_config` function.
 The link should be forced up or down appropriately in the
 :c:func:`mac_link_up` and :c:func:`mac_link_down` functions.

 .. code-block:: none

   &eth {
     managed = "in-band-status";
     phy = <&phy>;
     phy-mode = "sgmii";
   };

 uses in-band mode, where results from the PHY's negotiation are passed
 to the MAC through the SGMII control word, and the MAC is expected to
 acknowledge the control word.  The :c:func:`mac_link_up` and
 :c:func:`mac_link_down` functions must not force the MAC side link
 up and down.

 Rough guide to converting a network driver to sfp/phylink
 =========================================================

 This guide briefly describes how to convert a network driver from
 phylib to the sfp/phylink support.  Please send patches to improve
 this documentation.

 1. Optionally split the network driver's phylib update function into
    three parts dealing with link-down, link-up and reconfiguring the
    MAC settings. This can be done as a separate preparation commit.

    An example of this preparation can be found in git commit fc548b991fb0.

 2. Replace::

 	select FIXED_PHY
 	select PHYLIB

    with::

 	select PHYLINK

    in the driver's Kconfig stanza.

 3. Add::

 	#include <linux/phylink.h>

    to the driver's list of header files.

 4. Add::

 	struct phylink *phylink;

    to the driver's private data structure.  We shall refer to the
    driver's private data pointer as ``priv`` below, and the driver's
    private data structure as ``struct foo_priv``.

 5. Replace the following functions:

    .. flat-table::
     :header-rows: 1
     :widths: 1 1
     :stub-columns: 0

     * - Original function
       - Replacement function
     * - phy_start(phydev)
       - phylink_start(priv->phylink)
     * - phy_stop(phydev)
       - phylink_stop(priv->phylink)
     * - phy_mii_ioctl(phydev, ifr, cmd)
       - phylink_mii_ioctl(priv->phylink, ifr, cmd)
     * - phy_ethtool_get_wol(phydev, wol)
       - phylink_ethtool_get_wol(priv->phylink, wol)
     * - phy_ethtool_set_wol(phydev, wol)
       - phylink_ethtool_set_wol(priv->phylink, wol)
     * - phy_disconnect(phydev)
       - phylink_disconnect_phy(priv->phylink)

    Please note that some of these functions must be called under the
    rtnl lock, and will warn if not. This will normally be the case,
    except if these are called from the driver suspend/resume paths.

 6. Add/replace ksettings get/set methods with:

    .. code-block:: c

     static int foo_ethtool_set_link_ksettings(struct net_device *dev,
 					     const struct ethtool_link_ksettings *cmd)
     {
 	struct foo_priv *priv = netdev_priv(dev);

 	return phylink_ethtool_ksettings_set(priv->phylink, cmd);
     }

     static int foo_ethtool_get_link_ksettings(struct net_device *dev,
 					     struct ethtool_link_ksettings *cmd)
     {
 	struct foo_priv *priv = netdev_priv(dev);

 	return phylink_ethtool_ksettings_get(priv->phylink, cmd);
     }

 7. Replace the call to:

 	phy_dev = of_phy_connect(dev, node, link_func, flags, phy_interface);

    and associated code with a call to:

 	err = phylink_of_phy_connect(priv->phylink, node, flags);

    For the most part, ``flags`` can be zero; these flags are passed to
    the of_phy_attach() inside this function call if a PHY is specified
    in the DT node ``node``.

    ``node`` should be the DT node which contains the network phy property,
    fixed link properties, and will also contain the sfp property.

    The setup of fixed links should also be removed; these are handled
    internally by phylink.

    of_phy_connect() was also passed a function pointer for link updates.
    This function is replaced by a different form of MAC updates
    described below in (8).

    Manipulation of the PHY's supported/advertised happens within phylink
    based on the validate callback, see below in (8).

    Note that the driver no longer needs to store the ``phy_interface``,
    and also note that ``phy_interface`` becomes a dynamic property,
    just like the speed, duplex etc. settings.

    Finally, note that the MAC driver has no direct access to the PHY
    anymore; that is because in the phylink model, the PHY can be
    dynamic.

 8. Add a :c:type:`struct phylink_mac_ops <phylink_mac_ops>` instance to
    the driver, which is a table of function pointers, and implement
    these functions. The old link update function for
    :c:func:`of_phy_connect` becomes three methods: :c:func:`mac_link_up`,
    :c:func:`mac_link_down`, and :c:func:`mac_config`. If step 1 was
    performed, then the functionality will have been split there.

    It is important that if in-band negotiation is used,
    :c:func:`mac_link_up` and :c:func:`mac_link_down` do not prevent the
    in-band negotiation from completing, since these functions are called
    when the in-band link state changes - otherwise the link will never
    come up.

    The :c:func:`validate` method should mask the supplied supported mask,
    and ``state->advertising`` with the supported ethtool link modes.
    These are the new ethtool link modes, so bitmask operations must be
    used. For an example, see drivers/net/ethernet/marvell/mvneta.c.

    The :c:func:`mac_link_state` method is used to read the link state
    from the MAC, and report back the settings that the MAC is currently
    using. This is particularly important for in-band negotiation
    methods such as 1000base-X and SGMII.

    The :c:func:`mac_config` method is used to update the MAC with the
    requested state, and must avoid unnecessarily taking the link down
    when making changes to the MAC configuration.  This means the
    function should modify the state and only take the link down when
    absolutely necessary to change the MAC configuration.  An example
    of how to do this can be found in :c:func:`mvneta_mac_config` in
    drivers/net/ethernet/marvell/mvneta.c.

    For further information on these methods, please see the inline
    documentation in :c:type:`struct phylink_mac_ops <phylink_mac_ops>`.

 9. Remove calls to of_parse_phandle() for the PHY,
    of_phy_register_fixed_link() for fixed links etc. from the probe
    function, and replace with:

    .. code-block:: c

 	struct phylink *phylink;

 	phylink = phylink_create(dev, node, phy_mode, &phylink_ops);
 	if (IS_ERR(phylink)) {
 		err = PTR_ERR(phylink);
 		fail probe;
 	}

 	priv->phylink = phylink;

    and arrange to destroy the phylink in the probe failure path as
    appropriate and the removal path too by calling:

    .. code-block:: c

 	phylink_destroy(priv->phylink);

 10. Arrange for MAC link state interrupts to be forwarded into
     phylink, via:

     .. code-block:: c

 	phylink_mac_change(priv->phylink, link_is_up);

     where ``link_is_up`` is true if the link is currently up or false
     otherwise.

 11. Verify that the driver does not call::

 	netif_carrier_on()
 	netif_carrier_off()

    as these will interfere with phylink's tracking of the link state,
    and cause phylink to omit calls via the :c:func:`mac_link_up` and
    :c:func:`mac_link_down` methods.

 Network drivers should call phylink_stop() and phylink_start() via their
 suspend/resume paths, which ensures that the appropriate
 :c:type:`struct phylink_mac_ops <phylink_mac_ops>` methods are called
 as necessary.

 For information describing the SFP cage in DT, please see the binding
 documentation in the kernel source tree
 ``Documentation/devicetree/bindings/net/sff,sfp.txt``
	.. SPDX-License-Identifier: GPL-2.0

	=======
	phylink
	=======

	Overview
	========

	phylink is a mechanism to support hot-pluggable networking modules
	without needing to re-initialise the adapter on hot-plug events.

	phylink supports conventional phylib-based setups, fixed link setups
	and SFP (Small Formfactor Pluggable) modules at present.

	Modes of operation
	==================

	phylink has several modes of operation, which depend on the firmware
	settings.

	1. PHY mode

	In PHY mode, we use phylib to read the current link settings from
	the PHY, and pass them to the MAC driver. We expect the MAC driver
	to configure exactly the modes that are specified without any
	negotiation being enabled on the link.

	2. Fixed mode

	Fixed mode is the same as PHY mode as far as the MAC driver is
	concerned.

	3. In-band mode

	In-band mode is used with 802.3z, SGMII and similar interface modes,
	and we are expecting to use and honor the in-band negotiation or
	control word sent across the serdes channel.

	By example, what this means is that:

	.. code-block:: none

	&eth {
	phy = <&phy>;
	phy-mode = "sgmii";
	};

	does not use in-band SGMII signalling. The PHY is expected to follow
	exactly the settings given to it in its :c:func:`mac_config` function.
	The link should be forced up or down appropriately in the
	:c:func:`mac_link_up` and :c:func:`mac_link_down` functions.

	.. code-block:: none

	&eth {
	managed = "in-band-status";
	phy = <&phy>;
	phy-mode = "sgmii";
	};

	uses in-band mode, where results from the PHY's negotiation are passed
	to the MAC through the SGMII control word, and the MAC is expected to
	acknowledge the control word. The :c:func:`mac_link_up` and
	:c:func:`mac_link_down` functions must not force the MAC side link
	up and down.

	Rough guide to converting a network driver to sfp/phylink
	=========================================================

	This guide briefly describes how to convert a network driver from
	phylib to the sfp/phylink support. Please send patches to improve
	this documentation.

	1. Optionally split the network driver's phylib update function into
	three parts dealing with link-down, link-up and reconfiguring the
	MAC settings. This can be done as a separate preparation commit.

	An example of this preparation can be found in git commit fc548b991fb0.

	2. Replace::

	select FIXED_PHY
	select PHYLIB

	with::

	select PHYLINK

	in the driver's Kconfig stanza.

	3. Add::

	#include <linux/phylink.h>

	to the driver's list of header files.

	4. Add::

	struct phylink *phylink;

	to the driver's private data structure. We shall refer to the
	driver's private data pointer as ``priv`` below, and the driver's
	private data structure as ``struct foo_priv``.

	5. Replace the following functions:

	.. flat-table::
	:header-rows: 1
	:widths: 1 1
	:stub-columns: 0

	* - Original function
	- Replacement function
	* - phy_start(phydev)
	- phylink_start(priv->phylink)
	* - phy_stop(phydev)
	- phylink_stop(priv->phylink)
	* - phy_mii_ioctl(phydev, ifr, cmd)
	- phylink_mii_ioctl(priv->phylink, ifr, cmd)
	* - phy_ethtool_get_wol(phydev, wol)
	- phylink_ethtool_get_wol(priv->phylink, wol)
	* - phy_ethtool_set_wol(phydev, wol)
	- phylink_ethtool_set_wol(priv->phylink, wol)
	* - phy_disconnect(phydev)
	- phylink_disconnect_phy(priv->phylink)

	Please note that some of these functions must be called under the
	rtnl lock, and will warn if not. This will normally be the case,
	except if these are called from the driver suspend/resume paths.

	6. Add/replace ksettings get/set methods with:

	.. code-block:: c

	static int foo_ethtool_set_link_ksettings(struct net_device *dev,
	const struct ethtool_link_ksettings *cmd)
	{
	struct foo_priv *priv = netdev_priv(dev);

	return phylink_ethtool_ksettings_set(priv->phylink, cmd);
	}

	static int foo_ethtool_get_link_ksettings(struct net_device *dev,
	struct ethtool_link_ksettings *cmd)
	{
	struct foo_priv *priv = netdev_priv(dev);

	return phylink_ethtool_ksettings_get(priv->phylink, cmd);
	}

	7. Replace the call to:

	phy_dev = of_phy_connect(dev, node, link_func, flags, phy_interface);

	and associated code with a call to:

	err = phylink_of_phy_connect(priv->phylink, node, flags);

	For the most part, ``flags`` can be zero; these flags are passed to
	the of_phy_attach() inside this function call if a PHY is specified
	in the DT node ``node``.

	``node`` should be the DT node which contains the network phy property,
	fixed link properties, and will also contain the sfp property.

	The setup of fixed links should also be removed; these are handled
	internally by phylink.

	of_phy_connect() was also passed a function pointer for link updates.
	This function is replaced by a different form of MAC updates
	described below in (8).

	Manipulation of the PHY's supported/advertised happens within phylink
	based on the validate callback, see below in (8).

	Note that the driver no longer needs to store the ``phy_interface``,
	and also note that ``phy_interface`` becomes a dynamic property,
	just like the speed, duplex etc. settings.

	Finally, note that the MAC driver has no direct access to the PHY
	anymore; that is because in the phylink model, the PHY can be
	dynamic.

	8. Add a :c:type:`struct phylink_mac_ops <phylink_mac_ops>` instance to
	the driver, which is a table of function pointers, and implement
	these functions. The old link update function for
	:c:func:`of_phy_connect` becomes three methods: :c:func:`mac_link_up`,
	:c:func:`mac_link_down`, and :c:func:`mac_config`. If step 1 was
	performed, then the functionality will have been split there.

	It is important that if in-band negotiation is used,
	:c:func:`mac_link_up` and :c:func:`mac_link_down` do not prevent the
	in-band negotiation from completing, since these functions are called
	when the in-band link state changes - otherwise the link will never
	come up.

	The :c:func:`validate` method should mask the supplied supported mask,
	and ``state->advertising`` with the supported ethtool link modes.
	These are the new ethtool link modes, so bitmask operations must be
	used. For an example, see drivers/net/ethernet/marvell/mvneta.c.

	The :c:func:`mac_link_state` method is used to read the link state
	from the MAC, and report back the settings that the MAC is currently
	using. This is particularly important for in-band negotiation
	methods such as 1000base-X and SGMII.

	The :c:func:`mac_config` method is used to update the MAC with the
	requested state, and must avoid unnecessarily taking the link down
	when making changes to the MAC configuration. This means the
	function should modify the state and only take the link down when
	absolutely necessary to change the MAC configuration. An example
	of how to do this can be found in :c:func:`mvneta_mac_config` in
	drivers/net/ethernet/marvell/mvneta.c.

	For further information on these methods, please see the inline
	documentation in :c:type:`struct phylink_mac_ops <phylink_mac_ops>`.

	9. Remove calls to of_parse_phandle() for the PHY,
	of_phy_register_fixed_link() for fixed links etc. from the probe
	function, and replace with:

	.. code-block:: c

	struct phylink *phylink;

	phylink = phylink_create(dev, node, phy_mode, &phylink_ops);
	if (IS_ERR(phylink)) {
	err = PTR_ERR(phylink);
	fail probe;
	}

	priv->phylink = phylink;

	and arrange to destroy the phylink in the probe failure path as
	appropriate and the removal path too by calling:

	.. code-block:: c

	phylink_destroy(priv->phylink);

	10. Arrange for MAC link state interrupts to be forwarded into
	phylink, via:

	.. code-block:: c

	phylink_mac_change(priv->phylink, link_is_up);

	where ``link_is_up`` is true if the link is currently up or false
	otherwise.

	11. Verify that the driver does not call::

	netif_carrier_on()
	netif_carrier_off()

	as these will interfere with phylink's tracking of the link state,
	and cause phylink to omit calls via the :c:func:`mac_link_up` and
	:c:func:`mac_link_down` methods.

	Network drivers should call phylink_stop() and phylink_start() via their
	suspend/resume paths, which ensures that the appropriate
	:c:type:`struct phylink_mac_ops <phylink_mac_ops>` methods are called
	as necessary.

	For information describing the SFP cage in DT, please see the binding
	documentation in the kernel source tree
	``Documentation/devicetree/bindings/net/sff,sfp.txt``