Documentation: networking: add cpsw switchdev based driver documentation

* Texas Instruments CPSW switchdev based ethernet driver 2.0

- Port renaming

On older udev versions renaming of ethX to swXpY will not be automatically

supported

In order to rename via udev:

ip -d link show dev sw0p1 | grep switchid

SUBSYSTEM=="net", ACTION=="add", ATTR{phys_switch_id}==<switchid>, \

        ATTR{phys_port_name}!="", NAME="sw0$attr{phys_port_name}"

====================

# Dual mac mode

====================

- The new (cpsw_new.c) driver is operating in dual-emac mode by default, thus

working as 2 individual network interfaces. Main differences from legacy CPSW

driver are:

 - optimized promiscuous mode: The P0_UNI_FLOOD (both ports) is enabled in

addition to ALLMULTI (current port) instead of ALE_BYPASS.

So, Ports in promiscuous mode will keep possibility of mcast and vlan filtering,

which is provides significant benefits when ports are joined to the same bridge,

but without enabling "switch" mode, or to different bridges.

 - learning disabled on ports as it make not too much sense for

   segregated ports - no forwarding in HW.

 - enabled basic support for devlink.

	devlink dev show

		platform/48484000.switch

	devlink dev param show

	platform/48484000.switch:

	name switch_mode type driver-specific

	values:

		cmode runtime value false

	name ale_bypass type driver-specific

	values:

		cmode runtime value false

Devlink configuration parameters

====================

See Documentation/networking/devlink-params-ti-cpsw-switch.txt

====================

# Bridging in dual mac mode

====================

The dual_mac mode requires two vids to be reserved for internal purposes,

which, by default, equal CPSW Port numbers. As result, bridge has to be

configured in vlan unaware mode or default_pvid has to be adjusted.

	ip link add name br0 type bridge

	ip link set dev br0 type bridge vlan_filtering 0

	echo 0 > /sys/class/net/br0/bridge/default_pvid

	ip link set dev sw0p1 master br0

	ip link set dev sw0p2 master br0

 - or -

	ip link add name br0 type bridge

	ip link set dev br0 type bridge vlan_filtering 0

	echo 100 > /sys/class/net/br0/bridge/default_pvid

	ip link set dev br0 type bridge vlan_filtering 1

	ip link set dev sw0p1 master br0

	ip link set dev sw0p2 master br0

====================

# Enabling "switch"

====================

The Switch mode can be enabled by configuring devlink driver parameter

"switch_mode" to 1/true:

	devlink dev param set platform/48484000.switch \

	name switch_mode value 1 cmode runtime

This can be done regardless of the state of Port's netdev devices - UP/DOWN, but

Port's netdev devices have to be in UP before joining to the bridge to avoid

overwriting of bridge configuration as CPSW switch driver copletly reloads its

configuration when first Port changes its state to UP.

When the both interfaces joined the bridge - CPSW switch driver will enable

marking packets with offload_fwd_mark flag unless "ale_bypass=0"

All configuration is implemented via switchdev API.

====================

# Bridge setup

====================

	devlink dev param set platform/48484000.switch \

	name switch_mode value 1 cmode runtime

	ip link add name br0 type bridge

	ip link set dev br0 type bridge ageing_time 1000

	ip link set dev sw0p1 up

	ip link set dev sw0p2 up

	ip link set dev sw0p1 master br0

	ip link set dev sw0p2 master br0

	[*] bridge vlan add dev br0 vid 1 pvid untagged self

[*] if vlan_filtering=1. where default_pvid=1

=================

# On/off STP

=================

ip link set dev BRDEV type bridge stp_state 1/0

Note. Steps [*] are mandatory.

====================

# VLAN configuration

====================

bridge vlan add dev br0 vid 1 pvid untagged self <---- add cpu port to VLAN 1

Note. This step is mandatory for bridge/default_pvid.

=================

# Add extra VLANs

=================

 1. untagged:

    bridge vlan add dev sw0p1 vid 100 pvid untagged master

    bridge vlan add dev sw0p2 vid 100 pvid untagged master

    bridge vlan add dev br0 vid 100 pvid untagged self <---- Add cpu port to VLAN100

 2. tagged:

    bridge vlan add dev sw0p1 vid 100 master

    bridge vlan add dev sw0p2 vid 100 master

    bridge vlan add dev br0 vid 100 pvid tagged self <---- Add cpu port to VLAN100

====

FDBs

====

FDBs are automatically added on the appropriate switch port upon detection

Manually adding FDBs:

bridge fdb add aa:bb:cc:dd:ee:ff dev sw0p1 master vlan 100

bridge fdb add aa:bb:cc:dd:ee:fe dev sw0p2 master <---- Add on all VLANs

====

MDBs

====

MDBs are automatically added on the appropriate switch port upon detection

Manually adding MDBs:

bridge mdb add dev br0 port sw0p1 grp 239.1.1.1 permanent vid 100

bridge mdb add dev br0 port sw0p1 grp 239.1.1.1 permanent <---- Add on all VLANs

==================

Multicast flooding

==================

CPU port mcast_flooding is always on

Turning flooding on/off on swithch ports:

bridge link set dev sw0p1 mcast_flood on/off

==================

Access and Trunk port

==================

 bridge vlan add dev sw0p1 vid 100 pvid untagged master

 bridge vlan add dev sw0p2 vid 100 master

 bridge vlan add dev br0 vid 100 self

 ip link add link br0 name br0.100 type vlan id 100

 Note. Setting PVID on Bridge device itself working only for

 default VLAN (default_pvid).

=====================

 NFS

=====================

The only way for NFS to work is by chrooting to a minimal environment when

switch configuration that will affect connectivity is needed.

Assuming you are booting NFS with eth1 interface(the script is hacky and

it's just there to prove NFS is doable).

setup.sh:

#!/bin/sh

mkdir proc

mount -t proc none /proc

ifconfig br0  > /dev/null

if [ $? -ne 0 ]; then

        echo "Setting up bridge"

        ip link add name br0 type bridge

        ip link set dev br0 type bridge ageing_time 1000

        ip link set dev br0 type bridge vlan_filtering 1

        ip link set eth1 down

        ip link set eth1 name sw0p1

        ip link set dev sw0p1 up

        ip link set dev sw0p2 up

        ip link set dev sw0p2 master br0

        ip link set dev sw0p1 master br0

        bridge vlan add dev br0 vid 1 pvid untagged self

        ifconfig sw0p1 0.0.0.0

        udhchc -i br0

fi

umount /proc

run_nfs.sh:

#!/bin/sh

mkdir /tmp/root/bin -p

mkdir /tmp/root/lib -p

cp -r /lib/ /tmp/root/

cp -r /bin/ /tmp/root/

cp /sbin/ip /tmp/root/bin

cp /sbin/bridge /tmp/root/bin

cp /sbin/ifconfig /tmp/root/bin

cp /sbin/udhcpc /tmp/root/bin

cp /path/to/setup.sh /tmp/root/bin

chroot /tmp/root/ busybox sh /bin/setup.sh

run ./run_nfs.sh

ale_bypass	[DEVICE, DRIVER-SPECIFIC]

		Allows to enable ALE_CONTROL(4).BYPASS mode for debug purposes.

		All packets will be sent to the Host port only if enabled.

		Type: bool

		Configuration mode: runtime

switch_mode	[DEVICE, DRIVER-SPECIFIC]

		Enable switch mode

		Type: bool

		Configuration mode: runtime