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Message-Id: <1571698228-30985-5-git-send-email-ioana.ciornei@nxp.com>
Date: Tue, 22 Oct 2019 01:50:28 +0300
From: Ioana Ciornei <ioana.ciornei@....com>
To: davem@...emloft.net, netdev@...r.kernel.org
Cc: laurentiu.tudor@....com, andrew@...n.ch, f.fainelli@...il.com,
rmk@...linux.org.uk, Ioana Ciornei <ioana.ciornei@....com>
Subject: [PATCH net-next 4/4] 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@....com>
---
.../device_drivers/freescale/dpaa2/index.rst | 1 +
.../freescale/dpaa2/mac-phy-support.rst | 191 +++++++++++++++++++++
MAINTAINERS | 2 +
3 files changed, 194 insertions(+)
create mode 100644 Documentation/networking/device_drivers/freescale/dpaa2/mac-phy-support.rst
diff --git a/Documentation/networking/device_drivers/freescale/dpaa2/index.rst b/Documentation/networking/device_drivers/freescale/dpaa2/index.rst
index 67bd87fe6c53..ee40fcc5ddff 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
+ mac-phy-support
diff --git a/Documentation/networking/device_drivers/freescale/dpaa2/mac-phy-support.rst b/Documentation/networking/device_drivers/freescale/dpaa2/mac-phy-support.rst
new file mode 100644
index 000000000000..51e6624fb774
--- /dev/null
+++ b/Documentation/networking/device_drivers/freescale/dpaa2/mac-phy-support.rst
@@ -0,0 +1,191 @@
+.. 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) 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.
+
+.. 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.
+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.
diff --git a/MAINTAINERS b/MAINTAINERS
index d0e562d3ce5b..fdc3c89a4a6d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5052,6 +5052,8 @@ F: drivers/net/ethernet/freescale/dpaa2/dpmac*
F: drivers/net/ethernet/freescale/dpaa2/dpkg.h
F: drivers/net/ethernet/freescale/dpaa2/Makefile
F: drivers/net/ethernet/freescale/dpaa2/Kconfig
+F: Documentation/networking/device_drivers/freescale/dpaa2/ethernet-driver.rst
+F: Documentation/networking/device_drivers/freescale/dpaa2/mac-phy-support.rst
DPAA2 ETHERNET SWITCH DRIVER
M: Ioana Radulescu <ruxandra.radulescu@....com>
--
1.9.1
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