• Try iperf3 speed test on Bananapi BPI-R2.
• Note the speed of gmac0 or gmac1 as DSA master.
• See if there are any retransmitions on iperf3.
  • No transmitions.

Variables

• Revert f63959c7eec3151c30a2ee0d351827b62e742dcb.

  • This is the cause.

• Do not set core clock to 500mhz for the non-mcm chip.

  • Does not help.

• Set delay in dsa mode too.

  • Does not help.

• Check Daniel Golle's upcoming patch that fixes packet loss on a MAC.

  • Does not help.

  [net-next,v10,08/12] net: ethernet: mtk_eth_soc: fix RX data corruption issue - Patchwork

• Disable flow control.

  • Does not help.

with these 3 Patches network-connection works, but only at ~624 Mbit/s in TX-Mode (started iperf3-client on r2 without -R) and massive retransmitts on first run, other direction is clean.

Can you also remove this from mt7530.c and do the test again? See if the 
performance changes at all.

         /* Set core clock into 500Mhz */
         core_write(priv, CORE_GSWPLL_GRP2,
                    RG_GSWPLL_POSDIV_500M(1) |
                    RG_GSWPLL_FBKDIV_500M(25));

with these disabled i have a bit better performance (625 Mbits/sec instead of 600) and no retransmitts on first iperf3-run.

not yet tried any rgmii-delay option (have no idea which is the right one on which position), but yes, mostly it does not improve performance...it simply does work or does not work.

regards Frank