Subject: Re: [PATCH net-next 4/4] net: documentation: add docs for MAC/PHY support in DPAA2

From: Russell King - ARM Linux admin <[email-masked]>
Date: Tue, 22 Oct 2019 09:14:04 +0100

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 <[email-masked]>
> ---
>  .../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 <[email-masked]>
> -- 
> 1.9.1
> 
> 
> 
> 

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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