.. SPDX-License-Identifier: GPL-2.0
.. include:: <isonum.txt>
=======================
DPAA2 MAC / PHY support
=======================
:Copyright: |copy| 2019 NXP
Overview
--------
The DPAA2 MAC / PHY support consists of a set of APIs that help DPAA2 network
drivers (dpaa2-eth, dpaa2-ethsw) interact with the PHY library.
DPAA2 Software Architecture
---------------------------
Among other DPAA2 objects, the fsl-mc bus exports DPNI objects (abstracting a
network interface) and DPMAC objects (abstracting a MAC). The dpaa2-eth driver
probes on the DPNI object and connects to and configures a DPMAC object with
the help of phylink.
Data connections may be established between a DPNI and a DPMAC, or between two
DPNIs. Depending on the connection type, the netif_carrier_[on/off] is handled
directly by the dpaa2-eth driver or by phylink.
.. code-block:: none
Sources of abstracted link state information presented by the MC firmware
+--------------------------------------+
+------------+ +---------+ | xgmac_mdio |
| net_device | | phylink |--| +-----+ +-----+ +-----+ +-----+ |
+------------+ +---------+ | | PHY | | PHY | | PHY | | PHY | |
| | | +-----+ +-----+ +-----+ +-----+ |
+------------------------------------+ | External MDIO bus |
| dpaa2-eth | +--------------------------------------+
+------------------------------------+
| | Linux
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| | MC firmware
| /| V
+----------+ / | +----------+
| | / | | |
| | | | | |
| DPNI |<------| |<------| DPMAC |
| | | | | |
| | \ |<---+ | |
+----------+ \ | | +----------+
\| |
|
+--------------------------------------+
| MC firmware polling MAC PCS for link |
| +-----+ +-----+ +-----+ +-----+ |
| | PCS | | PCS | | PCS | | PCS | |
| +-----+ +-----+ +-----+ +-----+ |
| Internal MDIO bus |
+--------------------------------------+
Depending on an MC firmware configuration setting, each MAC may be in one of two modes:
- DPMAC_LINK_TYPE_FIXED: the link state management is handled exclusively by
the MC firmware by polling the MAC PCS. Without the need to register a
phylink instance, the dpaa2-eth driver will not bind to the connected dpmac
object at all.
- DPMAC_LINK_TYPE_PHY: The MC firmware is left waiting for link state update
events, but those are in fact passed strictly between the dpaa2-mac (based on
phylink) and its attached net_device driver (dpaa2-eth, dpaa2-ethsw),
effectively bypassing the firmware.
Implementation
--------------
At probe time or when a DPNI's endpoint is dynamically changed, the dpaa2-eth
is responsible to find out if the peer object is a DPMAC and if this is the
case, to integrate it with PHYLINK using the dpaa2_mac_connect() API, which
will do the following:
- look up the device tree for PHYLINK-compatible of binding (phy-handle)
- will create a PHYLINK instance associated with the received net_device
- connect to the PHY using phylink_of_phy_connect()
The following phylink_mac_ops callback are implemented:
- .validate() will populate the supported linkmodes with the MAC capabilities
only when the phy_interface_t is RGMII_* (at the moment, this is the only
link type supported by the driver).
- .mac_config() will configure the MAC in the new configuration using the
dpmac_set_link_state() MC firmware API.
- .mac_link_up() / .mac_link_down() will update the MAC link using the same
API described above.
At driver unbind() or when the DPNI object is disconnected from the DPMAC, the
dpaa2-eth driver calls dpaa2_mac_disconnect() which will, in turn, disconnect
from the PHY and destroy the PHYLINK instance.
In case of a DPNI-DPMAC connection, an 'ip link set dev eth0 up' would start
the following sequence of operations:
(1) phylink_start() called from .dev_open().
(2) The .mac_config() and .mac_link_up() callbacks are called by PHYLINK.
(3) In order to configure the HW MAC, the MC Firmware API
dpmac_set_link_state() is called.
(4) The firmware will eventually setup the HW MAC in the new configuration.
(5) A netif_carrier_on() call is made directly from PHYLINK on the associated
net_device.
(6) The dpaa2-eth driver handles the LINK_STATE_CHANGE irq in order to
enable/disable Rx taildrop based on the pause frame settings.
.. code-block:: none
+---------+ +---------+
| PHYLINK |-------------->| eth0 |
+---------+ (5) +---------+
(1) ^ |
| |
| v (2)
+-----------------------------------+
| dpaa2-eth |
+-----------------------------------+
| ^ (6)
| |
v (3) |
+---------+---------------+---------+
| DPMAC | | DPNI |
+---------+ +---------+
| MC Firmware |
+-----------------------------------+
|
|
v (4)
+-----------------------------------+
| HW MAC |
+-----------------------------------+
In case of a DPNI-DPNI connection, a usual sequence of operations looks like
the following:
(1) ip link set dev eth0 up
(2) The dpni_enable() MC API called on the associated fsl_mc_device.
(3) ip link set dev eth1 up
(4) The dpni_enable() MC API called on the associated fsl_mc_device.
(5) The LINK_STATE_CHANGED irq is received by both instances of the dpaa2-eth
driver because now the operational link state is up.
(6) The netif_carrier_on() is called on the exported net_device from
link_state_update().
.. code-block:: none
+---------+ +---------+
| eth0 | | eth1 |
+---------+ +---------+
| ^ ^ |
| | | |
(1) v | (6) (6) | v (3)
+---------+ +---------+
|dpaa2-eth| |dpaa2-eth|
+---------+ +---------+
| ^ ^ |
| | | |
(2) v | (5) (5) | v (4)
+---------+---------------+---------+
| DPNI | | DPNI |
+---------+ +---------+
| MC Firmware |
+-----------------------------------+
Exported API
------------
Any DPAA2 driver that drivers endpoints of DPMAC objects should service its
_EVENT_ENDPOINT_CHANGED irq and connect/disconnect from the associated DPMAC
when necessary using the below listed API::
- int dpaa2_mac_connect(struct dpaa2_mac *mac);
- void dpaa2_mac_disconnect(struct dpaa2_mac *mac);
A phylink integration is necessary only when the partner DPMAC is not of
``TYPE_FIXED``. This means it is either of ``TYPE_PHY``, or of
``TYPE_BACKPLANE`` (the difference being the two that in the ``TYPE_BACKPLANE``
mode, the MC firmware does not access the PCS registers). One can check for
this condition using the following helper::
- static inline bool dpaa2_mac_is_type_phy(struct dpaa2_mac *mac);
Before connection to a MAC, the caller must allocate and populate the
dpaa2_mac structure with the associated net_device, a pointer to the MC portal
to be used and the actual fsl_mc_device structure of the DPMAC.
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