Re: [PATCH v3 0/7] net: dsa: mt7530: support EcoNet EN751221

[Cristian Papa <pcristian292@gmail.com>]

Hi Caleb,

I tested v3 on a TP-Link Archer XR500v v1 (EN7526G: on-die switch plus the
MCM gigabit switch).

Setup: OpenWrt with kernel 6.18.44. I took the four mt7530 files from
econet_eth at 3a8bcd2e6398 (they contain every line added by 1/7, 3/7,
4/7, 5/7 and 7/7 of v3) and booted from RAM over TFTP, nothing written to
flash.

With the DT from en751221g.dtsi in openwrt#25330 (MCM "econet,en751221",
no "mediatek,mcm", dsa,member <0 1> on the on-die switch and <0 0> on the
MCM):

- 18/18 boots: all 10 TRGMII lanes found a window, no "calibration
  failed", "TRGMII inter-switch link initialized", DSA tree set up, ping
  over lan4.
- The chosen taps were stable across boots (+/-1): SoC->MCM 15-22,
  MCM->SoC 27-29. In the SoC->MCM direction the window always starts at
  tap 0.
- 6 of those boots ran iperf3 for 6 s each way through lan4: 0 RX CRC
  errors on on-die port 5 (~1.05M frames) and on MCM port 6 (~1.29M
  frames). In 4 of 10 boots MCM port 6 already had 1 CRC error before any
  traffic, probably from the calibration; it did not grow.

Following the binding in 6/7, the MCM does not come up on this board:

- "econet,en751221-gswitch": mt7530-mdio.c in 7/7 still matches
  "econet,en751221", so nothing probes the MCM and there are no LAN
  ports.
- "mediatek,mcm", which the binding requires for -gswitch: the probe
  fails with "Couldn't get our reset line", since nothing provides an
  "mcm" reset yet (the TODO in en751221g.dtsi).

So I think 7/7 should match the new compatible, and the binding should not
require "mediatek,mcm" while there is no "mcm" reset for the EN751221.

Not covered yet: cold boots, and the other LAN ports beyond link-up on
lan3/lan4. I'm happy to give a Tested-by once the compatible strings line
up, and to rerun anything you'd like; the full boot logs are available.

Thanks,
Cristian