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Date: Fri, 14 Jun 2019 02:55:53 +0300
From: Ioana Ciornei <ioana.ciornei@....com>
To: linux@...linux.org.uk, hkallweit1@...il.com, f.fainelli@...il.com,
andrew@...n.ch, davem@...emloft.net
Cc: netdev@...r.kernel.org, alexandru.marginean@....com,
ruxandra.radulescu@....com, Ioana Ciornei <ioana.ciornei@....com>
Subject: [PATCH RFC 6/6] net: documentation: add MAC/PHY proxy driver documentation
Add documentation file for the dpaa2-mac driver. This describes the
architecture and implementation of the proxy interface between phylink
and dpaa2-eth.
Signed-off-by: Ioana Ciornei <ioana.ciornei@....com>
---
.../freescale/dpaa2/dpmac-driver.rst | 159 +++++++++++++++++++++
.../device_drivers/freescale/dpaa2/index.rst | 1 +
MAINTAINERS | 1 +
3 files changed, 161 insertions(+)
create mode 100644 Documentation/networking/device_drivers/freescale/dpaa2/dpmac-driver.rst
diff --git a/Documentation/networking/device_drivers/freescale/dpaa2/dpmac-driver.rst b/Documentation/networking/device_drivers/freescale/dpaa2/dpmac-driver.rst
new file mode 100644
index 000000000000..ad09aa1c921e
--- /dev/null
+++ b/Documentation/networking/device_drivers/freescale/dpaa2/dpmac-driver.rst
@@ -0,0 +1,159 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. include:: <isonum.txt>
+
+===============================
+DPAA2 MAC / PHY proxy interface
+===============================
+
+:Copyright: |copy| 2019 NXP
+
+
+Overview
+--------
+
+The DPAA2 MAC / PHY proxy interface driver binds to DPAA2 DPMAC objects, which
+are dynamically discovered on the fsl-mc bus. Once probed, the driver looks up
+the device tree for PHYLINK-compatible OF bindings (phy-handle) and does the
+following:
+
+- registers itself with the Management Complex (MC) firmware to receive
+ interrupts for:
+
+ - Link up/down (on the PHY)
+ - Link configuration changes requested
+
+- creates a PHYLINK instance based on its device_node and connects to the
+ specified PHY
+
+- notifies the MC firmware of any link status change received from PHYLINK
+
+
+DPAA2 Software Architecture
+---------------------------
+
+Among other DPAA2 objects, the fsl-mc bus exports DPNI objects (abstracting a
+network interface) and DPMAC objects (abstracting a MAC) which are probed and
+managed by two different drivers: dpaa2-eth and dpaa2-mac.
+
+Data connections may be established between a DPNI and a DPMAC, or between two
+DPNIs. A DPNI may be directly assigned to a guest software partition, whereas
+a DPMAC object is always managed from the root (most privileged) container.
+
+For netif_carrier_on/netif_carrier_off, the MC firmware presents to the DPNI
+object an abstracted view of the link state:
+
+.. 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 dpaa2-mac +--------------------------------------+
+ ^ |
+ | | 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.
+
+- DPMAC_LINK_TYPE_PHY: the link state comes as an input to the MC firmware
+ itself through the dpmac_set_link_cfg() function.
+
+In both cases, the MC firmware emits an abstracted link state information to
+the connected DPNI which can be retrieved using the dpni_get_link_state()
+command. This way, users of DPNI interfaces are not required to implement
+complex PHY drivers.
+
+In DPMAC_LINK_TYPE_FIXED mode, a dpaa2-mac driver is not necessary.
+
+Implementation
+--------------
+
+After the system boots and the DPNIs are connected to DPMACs, all network
+interfaces have their respective net_devices exported and ready to be used.
+
+When the dpaa2-eth interface link is requested to go up, the following set of
+steps must happen::
+
+ Inter-driver communication between fsl-mc bus objects through the MC firmware
+
+ +-----------+ +-------------+
+ | | ------------------> | MC firmware |
+ | dpaa2-eth | (1) | |
+ | | < - - - - - - - - - | |
+ +-----------+ (6) | |
+ | | |
+ eth0 | |
+ | |
+ +---------+ +-----------+ | |
+ | PHYLINK | <------------ | dpaa2-mac | <------------------ | |
+ | | (3) | | (2) | |
+ | | | | | |
+ | | ------------> | | ------------------> | |
+ +---------+ (4) +-----------+ (5) | |
+ +-------------+
+
+ (1) dpni_enable() - Enable network interface, allowing receiving/sending frames
+ (2) MC sends DPMAC_IRQ_EVENT_LINK_UP_REQ to the dpmac object
+ (3) The dpaa2-mac driver calls phylink_start() on the PHYLINK instance
+ (4) PHYLINK notifies the dpaa2-mac driver through the .mac_config and
+ .mac_link_up calbacks
+ (5) With the information received in the phylink_link_state structure, the
+ dpaa2-mac driver informs the firmware of the new link state
+ (6) At any later time, the dpaa2-eth driver may find the updated link state
+ by calling dpni_get_link_state() to the MC firmware
+
+And the following output is seen in the console::
+
+ # ip link set dev eth0 up
+ [14894.837845] fsl_dpaa2_mac dpmac.17: configuring for phy/rgmii-id link mode
+ [14896.895953] fsl_dpaa2_mac dpmac.17: Link is Up - 1Gbps/Full - flow control off
+ [14896.897478] fsl_dpaa2_eth dpni.0 eth1: Link Event: state up
+
+
+In case of a link change requested by the user through ethtool on the dpaa2-eth
+interface, the same calling flow as above happens between DPNI driver -> MC ->
+DPMAC driver -> PHYLINK and back. However in this case the functions are
+different::
+
+ (1) The dpaa2-eth driver, on the .set_link_ksettings() callback, sends a
+ dpni_set_link_cfg() to the firmware, informing it about the new
+ configuration requested. This firmware command will carry link state
+ options such as autoneg on/off, advertising, duplex, speed.
+ (2) The MC firmware will trigger an DPMAC_IRQ_EVENT_LINK_CFG_REQ.
+ (3) Upon receiving the interrupt, the dpaa2-mac driver will get the
+ requested configuration parameters and construct a new
+ ethtool_link_ksettings command based on them. This will be passed to
+ phylink_ethtool_ksettings_set.
+ (4) If the link state changes, the .mac_config() routine will be called by
+ PHYLINK.
+ (5) The dpaa2-mac driver passes the current state of link from the
+ phylink_link_state argument and notifies the firmware of all the changes
+ (autoneg, speed, etc) through another dpmac_set_link_state() command.
+ (6) Same as above, the DPNI driver can retrieve the updated link state
+ information at a later time through dpni_get_link_state().
diff --git a/Documentation/networking/device_drivers/freescale/dpaa2/index.rst b/Documentation/networking/device_drivers/freescale/dpaa2/index.rst
index 67bd87fe6c53..2cd5d728da19 100644
--- a/Documentation/networking/device_drivers/freescale/dpaa2/index.rst
+++ b/Documentation/networking/device_drivers/freescale/dpaa2/index.rst
@@ -8,3 +8,4 @@ DPAA2 Documentation
overview
dpio-driver
ethernet-driver
+ dpmac-driver
diff --git a/MAINTAINERS b/MAINTAINERS
index a024ab2b2548..0b9c1df5ff8c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4935,6 +4935,7 @@ L: netdev@...r.kernel.org
S: Maintained
F: drivers/net/ethernet/freescale/dpaa2/dpaa2-mac*
F: drivers/net/ethernet/freescale/dpaa2/dpmac*
+F: Documentation/networking/device_drivers/freescale/dpaa2/dpmac-driver.rst
DPT_I2O SCSI RAID DRIVER
M: Adaptec OEM Raid Solutions <aacraid@...rosemi.com>
--
1.9.1
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