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:
phylink_start()called from .dev_open().- The .
mac_config()and .mac_link_up()callbacks are called by PHYLINK. - In order to configure the HW MAC, the MC Firmware API dpmac_set_link_state() is called.
- The firmware will eventually setup the HW MAC in the new configuration.
- A
netif_carrier_on()call is made directly from PHYLINK on the associated net_device. - 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:
- ip link set dev eth0 up
- The dpni_enable() MC API called on the associated fsl_mc_device.
- ip link set dev eth1 up
- The dpni_enable() MC API called on the associated fsl_mc_device.
- The LINK_STATE_CHANGED irq is received by both instances of the dpaa2-eth driver because now the operational link state is up.
- 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.