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

From: Ioana Ciornei <ioana.ciornei@nxp.com>
Date: 2019-10-22 10:03:29

quoted

This mentions phylink, but I never got the other patches of the
series which presumably implement this idea.

Hi Russell,

I copied you to the entire series. Anyhow, here is a link to the entire patch

set -
https://www.spinics.net/lists/netdev/msg606466.html.

Please avoid using rmk@armlinux.org.uk for patches.  dspam doesn't know
about Linux stuff there, and so files emails that contain patches into spam.
Please use linux@armlinux.org.uk for all kernel related work, as per my
addresses in the MAINTAINERS file.

I now need to manually transfer all those emails...

I'll keep that in mind for the future. Sorry for the trouble.

quoted

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:

I looked through the branch and it seems that the approach you are going

for is similar (if not exactly the same) as the one from my previous patch set
that was shut down.

quoted

Also, sorry for the delay on sending another set but it takes a bit of time to

consider all the implications of changing the entire architecture of the
solution to better fit the upstream model.

quoted

Ioana

quoted

 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:

quoted

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@nxp.com>
---
 .../device_drivers/freescale/dpaa2/index.rst       |   1 +
 .../freescale/dpaa2/mac-phy-support.rst            | 191

+++++++++++++++++++++

quoted

 MAINTAINERS                                        |   2 +
 3 files changed, 194 insertions(+)  create mode 100644
Documentation/networking/device_drivers/freescale/dpaa2/mac-phy-

su

quoted

quoted
quoted
ppor
t.rst

diff --git

a/Documentation/networking/device_drivers/freescale/dpaa2/index.rs

quoted

quoted
quoted
t

b/Documentation/networking/device_drivers/freescale/dpaa2/index.rs

quoted

t index 67bd87fe6c53..ee40fcc5ddff 100644
---

a/Documentation/networking/device_drivers/freescale/dpaa2/index.rs

quoted

quoted
quoted
t
+++

b/Documentation/networking/device_drivers/freescale/dpaa2/inde

quoted

+++ x.rs
+++ t

@@ -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-

quoted

supp
ort.rst
b/Documentation/networking/device_drivers/freescale/dpaa2/mac-

phy-

quoted

supp
ort.rst
new file mode 100644
index 000000000000..51e6624fb774

--- /dev/null
+++

b/Documentation/networking/device_drivers/freescale/dpaa2/mac-

quoted

+++ 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.

quoted

+
+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.

quoted

+
+.. code-block:: none
+
+  Sources of abstracted link state information presented by the
+ MC firmware
+
+                                               +--------------------------------------+
+  +------------+                  +---------+  |                           xgmac_mdio |
+  | net_device |                  | phylink |--|  +-----+  +-----+  +-----+  +-----+

quoted

+  +------------+                  +---------+  |  | PHY |  | PHY |  | PHY |  | PHY |  |
+        |                             |        |  +-----+  +-----+  +-----+  +-----+  |
+      +------------------------------------+   |                    External MDIO bus |
+      |            dpaa2-eth               |   +--------------------------------------+
+      +------------------------------------+
+        |                             |                                           Linux
+

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~

quoted

~~~~~~~~~~~~~~~~~~~~

quoted

+        |                             |                                     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:

quoted

+
+- 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

quoted

+   only when the phy_interface_t is RGMII_* (at the moment, this is

the only

quoted

+   link type supported by the driver).
+
+ - .mac_config() will configure the MAC in the new configuration using

the

quoted

+   dpmac_set_link_state() MC firmware API.
+
+ - .mac_link_up() / .mac_link_down() will update the MAC link using

the same

quoted

+   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.

quoted

+
+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.

quoted

+(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.

quoted

+(5) A netif_carrier_on() call is made directly from PHYLINK on the

associated

quoted

+    net_device.
+(6) The dpaa2-eth driver handles the LINK_STATE_CHANGE irq in

order to

quoted

+    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

quoted

+    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::

quoted

+
+ - 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.

quoted

+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.

quoted

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*

quoted

 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/ethern
et-

quoted

quoted
driver.rst
quoted
+F:

	Documentation/networking/device_drivers/freescale/dpaa2/mac-
phy-

quoted

support.rst

quoted

 DPAA2 ETHERNET SWITCH DRIVER
 M:	Ioana Radulescu [off-list ref]
--
1.9.1

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