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Message-ID: <20191022081404.GN25745@shell.armlinux.org.uk>
Date: Tue, 22 Oct 2019 09:14:04 +0100
From: Russell King - ARM Linux admin <linux@...linux.org.uk>
To: Ioana Ciornei <ioana.ciornei@....com>
Cc: davem@...emloft.net, netdev@...r.kernel.org,
laurentiu.tudor@....com, andrew@...n.ch, f.fainelli@...il.com
Subject: Re: [PATCH net-next 4/4] net: documentation: add docs for MAC/PHY
support in DPAA2
This mentions phylink, but I never got the other patches of the series
which presumably implement this idea.
Please also note that I gave up waiting for another set, and as I now
have LX2160A hardware, I ended up writing my own version, which can be
found in my cex7 branch at:
git://git.armlinux.org.uk/~rmk/linux-arm.git cex7
http://git.armlinux.org.uk/cgit/linux-arm.git/log/?h=cex7
On Tue, Oct 22, 2019 at 01:50:28AM +0300, Ioana Ciornei wrote:
> 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
>
>
>
>
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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