[RFC 0/2 net-next] net: dsa: MT7628 embedded switch initial support

[Joris Vaisvila <joey@tinyisr.com>]

Hello,

This RFC adds initial support for the basic functionality needed to
operate the MT7628 embedded switch.

The driver configures the switch to isolate each port and does not
offload any bridge functions, so all of the forwarding is done in
software. Bridge and VLAN offloading are possible but omitted to
simplify this initial patch set.

The special tag currently overlaps some functionality with tag_8021q,
but it enables precise TX handling and (more) precise RX handling for
future VLAN offloading.

Tested on MT7628AN with 5 100mbps ports. All 5 ports were tested for
correct forwarding with two devices.

# Request for comments:

- What would be an acceptable way to present the undocumented phy init
  in mt7628_vendor_phys_init and switch_init?

- Should I aim to set all register default values for general switch
  config or is relying on the documented switch reset state acceptable?

- I am also looking for any and all feedback on the architecture and
  coding style of this driver.

Thank you for your time and feedback.

Joris Vaisvila (2):
  net: dsa: initial MT7628 special tag driver
  net: dsa: initial support for MT7628 embedded switch

 drivers/net/dsa/Kconfig  |   6 +
 drivers/net/dsa/Makefile |   1 +
 drivers/net/dsa/mt7628.c | 567 +++++++++++++++++++++++++++++++++++++++
 include/net/dsa.h        |   2 +
 net/dsa/Kconfig          |   6 +
 net/dsa/Makefile         |   1 +
 net/dsa/tag_mt7628.c     |  85 ++++++
 7 files changed, 668 insertions(+)
 create mode 100644 drivers/net/dsa/mt7628.c
 create mode 100644 net/dsa/tag_mt7628.c

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2.53.0