[PATCH v3 net-next 00/12] ethtool support for IEEE 802.3 MAC Merge layer

Vladimir Oltean
2023-01-17T09:02:11Z

Change log
----------

v2->v3:
- made get_mm return int instead of void
- deleted ETHTOOL_A_MM_SUPPORTED
- renamed ETHTOOL_A_MM_ADD_FRAG_SIZE to ETHTOOL_A_MM_TX_MIN_FRAG_SIZE
- introduced ETHTOOL_A_MM_RX_MIN_FRAG_SIZE
- cleaned up documentation
- rebased on top of PLCA changes
- renamed ETHTOOL_STATS_SRC_* to ETHTOOL_MAC_STATS_SRC_*
v2 at:
https://patchwork.kernel.org/project/netdevbpf/cover/20230111161706.1465242-1-vladimir.oltean@nxp.com/

v1->v2:
I've decided to focus just on the MAC Merge layer for now, which is why
I am able to submit this patch set as non-RFC.
v1 (RFC) at:
https://patchwork.kernel.org/project/netdevbpf/cover/20220816222920.1952936-1-vladimir.oltean@nxp.com/

What is being introduced
------------------------

TL;DR: a MAC Merge layer as defined by IEEE 802.3-2018, clause 99
(interspersing of express traffic). This is controlled through ethtool
netlink (ETHTOOL_MSG_MM_GET, ETHTOOL_MSG_MM_SET). The raw ethtool
commands are posted here:
https://patchwork.kernel.org/project/netdevbpf/cover/20230111153638.1454687-1-vladimir.oltean@nxp.com/

The MAC Merge layer has its own statistics counters
(ethtool --include-statistics --show-mm swp0) as well as two member
MACs, the statistics of which can be queried individually, through a new
ethtool netlink attribute, corresponding to:

$ ethtool -I --show-pause eno2 --src aggregate
$ ethtool -S eno2 --groups eth-mac eth-phy eth-ctrl rmon -- --src pmac

The core properties of the MAC Merge layer are described in great detail
in patches 02/12 and 03/12. They can be viewed in "make htmldocs" format.

Devices for which the API is supported
--------------------------------------

I decided to start with the Ethernet switch on NXP LS1028A (Felix)
because of the smaller patch set. I also have support for the ENETC
controller pending.

I would like to get confirmation that the UAPI being proposed here will
not restrict any use cases known by other hardware vendors.

Why is support for preemptible traffic classes not here?
--------------------------------------------------------

There is legitimate concern whether the 802.1Q portion of the standard
(which traffic classes go to the eMAC and which to the pMAC) should be
modeled in Linux using tc or using another UAPI. I think that is
stalling the entire series, but should be discussed separately instead.
Removing FP adminStatus support makes me confident enough to submit this
patch set without an RFC tag (meaning: I wouldn't mind if it was merged
as is).

What is submitted here is sufficient for an LLDP daemon to do its job.
I've patched openlldp to advertise and configure frame preemption:
https://github.com/vladimiroltean/openlldp/tree/frame-preemption-v3

In case someone wants to try it out, here are some commands I've used.

# Configure the interfaces to receive and transmit LLDP Data Units
lldptool -L -i eno0 adminStatus=rxtx
lldptool -L -i swp0 adminStatus=rxtx
# Enable the transmission of certain TLVs on switch's interface
lldptool -T -i eno0 -V addEthCap enableTx=yes
lldptool -T -i swp0 -V addEthCap enableTx=yes
# Query LLDP statistics on switch's interface
lldptool -S -i swp0
# Query the received neighbor TLVs
lldptool -i swp0 -t -n -V addEthCap
Additional Ethernet Capabilities TLV
Preemption capability supported
Preemption capability enabled
Preemption capability active
Additional fragment size: 60 octets

So using this patch set, lldpad will be able to advertise and configure
frame preemption, but still, no data packet will be sent as preemptible
over the link, because there is no UAPI to control which traffic classes
are sent as preemptible and which as express.

Preemptable or preemptible?
---------------------------

IEEE 802.3 uses "preemptable" throughout. IEEE 802.1Q uses "preemptible"
throughout. Because the definition of "preemptible" falls under 802.1Q's
jurisdiction and 802.3 just references it, I went with the 802.1Q naming
even where supporting an 802.3 feature. Also, checkpatch agrees with this.

Vladimir Oltean (12):
net: ethtool: netlink: introduce ethnl_update_bool()
net: ethtool: add support for MAC Merge layer
docs: ethtool-netlink: document interface for MAC Merge layer
net: ethtool: netlink: retrieve stats from multiple sources (eMAC,
pMAC)
docs: ethtool: document ETHTOOL_A_STATS_SRC and
ETHTOOL_A_PAUSE_STATS_SRC
net: ethtool: add helpers for aggregate statistics
net: ethtool: add helpers for MM fragment size translation
net: dsa: add plumbing for changing and getting MAC merge layer state
net: mscc: ocelot: allow ocelot_stat_layout elements with no name
net: mscc: ocelot: hide access to ocelot_stats_layout behind a helper
net: mscc: ocelot: export ethtool MAC Merge stats for Felix VSC9959
net: mscc: ocelot: add MAC Merge layer support for VSC9959

Documentation/networking/ethtool-netlink.rst | 107 ++++++
Documentation/networking/statistics.rst | 1 +
drivers/net/dsa/ocelot/felix.c | 28 ++
drivers/net/dsa/ocelot/felix_vsc9959.c | 57 +++-
drivers/net/ethernet/mscc/Makefile | 1 +
drivers/net/ethernet/mscc/ocelot.c | 18 +-
drivers/net/ethernet/mscc/ocelot.h | 2 +
drivers/net/ethernet/mscc/ocelot_mm.c | 214 ++++++++++++
drivers/net/ethernet/mscc/ocelot_stats.c | 331 +++++++++++++++++--
include/linux/ethtool.h | 248 +++++++++++---
include/net/dsa.h | 11 +
include/soc/mscc/ocelot.h | 58 ++++
include/soc/mscc/ocelot_dev.h | 23 ++
include/uapi/linux/ethtool.h | 43 +++
include/uapi/linux/ethtool_netlink.h | 50 +++
net/dsa/slave.c | 37 +++
net/ethtool/Makefile | 4 +-
net/ethtool/common.h | 2 +
net/ethtool/mm.c | 271 +++++++++++++++
net/ethtool/netlink.c | 19 ++
net/ethtool/netlink.h | 34 +-
net/ethtool/pause.c | 48 +++
net/ethtool/stats.c | 159 ++++++++-
23 files changed, 1688 insertions(+), 78 deletions(-)
create mode 100644 drivers/net/ethernet/mscc/ocelot_mm.c
create mode 100644 net/ethtool/mm.c

--
2.34.1