DPAA2 MAC / PHY support

Copyright:© 2019 NXP

Overview

The DPAA2 MAC / PHY support consists of a set of APIs that help DPAA2 network drivers (dpaa2-eth, dpaa2-ethsw) interract 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.

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.
+---------+               +---------+
| 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().
+---------+               +---------+
|  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. One can check for this condition using the below API:

- bool dpaa2_mac_is_type_fixed(struct fsl_mc_device *dpmac_dev,struct fsl_mc_io *mc_io);

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.