forked from Minki/linux
net: documentation: add docs for MAC/PHY support in DPAA2
Add documentation file for the MAC/PHY support in the DPAA2 architecture. This describes the architecture and implementation of the interface between phylink and a DPAA2 network driver. Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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Ioana Ciornei
David S. Miller
parent
7194792308
commit
ecc5fe7d2b
@ -8,3 +8,4 @@ DPAA2 Documentation
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overview
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dpio-driver
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ethernet-driver
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mac-phy-support
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@ -0,0 +1,191 @@
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.. SPDX-License-Identifier: GPL-2.0
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.. include:: <isonum.txt>
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=======================
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DPAA2 MAC / PHY support
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=======================
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:Copyright: |copy| 2019 NXP
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Overview
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--------
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The DPAA2 MAC / PHY support consists of a set of APIs that help DPAA2 network
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drivers (dpaa2-eth, dpaa2-ethsw) interract with the PHY library.
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DPAA2 Software Architecture
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---------------------------
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Among other DPAA2 objects, the fsl-mc bus exports DPNI objects (abstracting a
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network interface) and DPMAC objects (abstracting a MAC). The dpaa2-eth driver
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probes on the DPNI object and connects to and configures a DPMAC object with
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the help of phylink.
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Data connections may be established between a DPNI and a DPMAC, or between two
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DPNIs. Depending on the connection type, the netif_carrier_[on/off] is handled
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directly by the dpaa2-eth driver or by phylink.
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.. code-block:: none
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Sources of abstracted link state information presented by the MC firmware
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+--------------------------------------+
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+------------+ +---------+ | xgmac_mdio |
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| net_device | | phylink |--| +-----+ +-----+ +-----+ +-----+ |
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+------------+ +---------+ | | PHY | | PHY | | PHY | | PHY | |
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| | | +-----+ +-----+ +-----+ +-----+ |
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+------------------------------------+ | External MDIO bus |
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| dpaa2-eth | +--------------------------------------+
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+------------------------------------+
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| | Linux
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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| | MC firmware
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| /| V
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+----------+ / | +----------+
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| | / | | |
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| | | | | |
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| DPNI |<------| |<------| DPMAC |
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| | | | | |
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| | \ |<---+ | |
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+----------+ \ | | +----------+
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\| |
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+--------------------------------------+
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| MC firmware polling MAC PCS for link |
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| +-----+ +-----+ +-----+ +-----+ |
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| | PCS | | PCS | | PCS | | PCS | |
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| +-----+ +-----+ +-----+ +-----+ |
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| Internal MDIO bus |
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+--------------------------------------+
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Depending on an MC firmware configuration setting, each MAC may be in one of two modes:
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- DPMAC_LINK_TYPE_FIXED: the link state management is handled exclusively by
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the MC firmware by polling the MAC PCS. Without the need to register a
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phylink instance, the dpaa2-eth driver will not bind to the connected dpmac
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object at all.
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- DPMAC_LINK_TYPE_PHY: The MC firmware is left waiting for link state update
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events, but those are in fact passed strictly between the dpaa2-mac (based on
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phylink) and its attached net_device driver (dpaa2-eth, dpaa2-ethsw),
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effectively bypassing the firmware.
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Implementation
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--------------
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At probe time or when a DPNI's endpoint is dynamically changed, the dpaa2-eth
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is responsible to find out if the peer object is a DPMAC and if this is the
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case, to integrate it with PHYLINK using the dpaa2_mac_connect() API, which
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will do the following:
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- look up the device tree for PHYLINK-compatible of binding (phy-handle)
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- will create a PHYLINK instance associated with the received net_device
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- connect to the PHY using phylink_of_phy_connect()
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The following phylink_mac_ops callback are implemented:
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- .validate() will populate the supported linkmodes with the MAC capabilities
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only when the phy_interface_t is RGMII_* (at the moment, this is the only
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link type supported by the driver).
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- .mac_config() will configure the MAC in the new configuration using the
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dpmac_set_link_state() MC firmware API.
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- .mac_link_up() / .mac_link_down() will update the MAC link using the same
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API described above.
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At driver unbind() or when the DPNI object is disconnected from the DPMAC, the
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dpaa2-eth driver calls dpaa2_mac_disconnect() which will, in turn, disconnect
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from the PHY and destroy the PHYLINK instance.
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In case of a DPNI-DPMAC connection, an 'ip link set dev eth0 up' would start
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the following sequence of operations:
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(1) phylink_start() called from .dev_open().
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(2) The .mac_config() and .mac_link_up() callbacks are called by PHYLINK.
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(3) In order to configure the HW MAC, the MC Firmware API
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dpmac_set_link_state() is called.
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(4) The firmware will eventually setup the HW MAC in the new configuration.
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(5) A netif_carrier_on() call is made directly from PHYLINK on the associated
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net_device.
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(6) The dpaa2-eth driver handles the LINK_STATE_CHANGE irq in order to
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enable/disable Rx taildrop based on the pause frame settings.
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.. code-block:: none
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+---------+ +---------+
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| PHYLINK |-------------->| eth0 |
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+---------+ (5) +---------+
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(1) ^ |
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| |
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| v (2)
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+-----------------------------------+
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| dpaa2-eth |
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+-----------------------------------+
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| ^ (6)
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| |
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v (3) |
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+---------+---------------+---------+
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| DPMAC | | DPNI |
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+---------+ +---------+
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| MC Firmware |
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+-----------------------------------+
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v (4)
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+-----------------------------------+
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| HW MAC |
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+-----------------------------------+
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In case of a DPNI-DPNI connection, a usual sequence of operations looks like
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the following:
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(1) ip link set dev eth0 up
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(2) The dpni_enable() MC API called on the associated fsl_mc_device.
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(3) ip link set dev eth1 up
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(4) The dpni_enable() MC API called on the associated fsl_mc_device.
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(5) The LINK_STATE_CHANGED irq is received by both instances of the dpaa2-eth
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driver because now the operational link state is up.
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(6) The netif_carrier_on() is called on the exported net_device from
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link_state_update().
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.. code-block:: none
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+---------+ +---------+
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| eth0 | | eth1 |
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+---------+ +---------+
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| ^ ^ |
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| | | |
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(1) v | (6) (6) | v (3)
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+---------+ +---------+
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|dpaa2-eth| |dpaa2-eth|
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+---------+ +---------+
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| ^ ^ |
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| | | |
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(2) v | (5) (5) | v (4)
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+---------+---------------+---------+
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| DPNI | | DPNI |
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+---------+ +---------+
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| MC Firmware |
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+-----------------------------------+
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Exported API
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------------
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Any DPAA2 driver that drivers endpoints of DPMAC objects should service its
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_EVENT_ENDPOINT_CHANGED irq and connect/disconnect from the associated DPMAC
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when necessary using the below listed API::
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- int dpaa2_mac_connect(struct dpaa2_mac *mac);
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- void dpaa2_mac_disconnect(struct dpaa2_mac *mac);
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A phylink integration is necessary only when the partner DPMAC is not of TYPE_FIXED.
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One can check for this condition using the below API::
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- bool dpaa2_mac_is_type_fixed(struct fsl_mc_device *dpmac_dev,struct fsl_mc_io *mc_io);
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Before connection to a MAC, the caller must allocate and populate the
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dpaa2_mac structure with the associated net_device, a pointer to the MC portal
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to be used and the actual fsl_mc_device structure of the DPMAC.
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@ -5059,6 +5059,8 @@ F: drivers/net/ethernet/freescale/dpaa2/dpmac*
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F: drivers/net/ethernet/freescale/dpaa2/dpkg.h
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F: drivers/net/ethernet/freescale/dpaa2/Makefile
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F: drivers/net/ethernet/freescale/dpaa2/Kconfig
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F: Documentation/networking/device_drivers/freescale/dpaa2/ethernet-driver.rst
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F: Documentation/networking/device_drivers/freescale/dpaa2/mac-phy-support.rst
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DPAA2 ETHERNET SWITCH DRIVER
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M: Ioana Radulescu <ruxandra.radulescu@nxp.com>
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