Hi Neil,

On Fri, Apr 30, 2021 at 10:16 AM Neil Armstrong [off-list ref] wrote:
[...]

quoted

quoted

+&ethmac {
+       pinctrl-0 = <&eth_pins>, <&eth_rgmii_pins>;
+       pinctrl-names = "default";
+       status = "okay";
+       phy-mode = "rgmii";
+       phy-handle = <&external_phy>;
+       amlogic,tx-delay-ns = <2>;

I haven't checked their u-boot code but some of the newer Amlogic BSPs
seem to let the PHY add the TX delay (which is also what the netdev
maintainers recommend)
that can be achieved by setting:
  phy-mode = "rgmii-txid";
and deleting the "amlogic,tx-delay-ns" property

Done, but what about when we use mainline U-boot here ?

I think it will work just fine if
- the PRG_ETH0/PRG_ETH1 register is programmed correctly (that's what
we have in dwmac-meson8b), which according to [0] is partially (RX
delay not being supported in u-boot yet) the case
- and the RTL8211F PHY driver can set the RX/TX delay on the PHY side,
which according to [1] it can

So I have not tried it but I think it should just work


Best regards,
Martin


[0] https://source.denx.de/u-boot/u-boot/-/blob/798424e8573a6b642a1bb507d41c1f73e6736e2e/drivers/net/dwmac_meson8b.c
[1] https://source.denx.de/u-boot/u-boot/-/blob/fa6539a3dcbf269121ca64084cff4c146fcdaf19/drivers/net/phy/realtek.c#L204

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