On 2/15/23 15:01, Andrew Lunn wrote:

On Wed, Feb 15, 2023 at 02:34:23AM +0200, Cristian Ciocaltea wrote:

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On 2/11/23 18:01, Andrew Lunn wrote:

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+  starfive,gtxclk-dlychain:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description: GTX clock delay chain setting

Please could you add more details to this. Is this controlling the
RGMII delays? 0ns or 2ns?

This is what gets written to JH7100_SYSMAIN_REGISTER49 and it's currently
set to 4 in patch 12/12. As already mentioned, I don't have the register
information in the datasheet, but I'll update this as soon as we get some
details.

I have seen what happens to this value, but i have no idea what it
actually means. And without knowing what it means, i cannot say if it
is being used correctly or not. And it could be related to the next
part of my comment...

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+    gmac: ethernet@10020000 {
+      compatible = "starfive,jh7100-dwmac", "snps,dwmac";
+      reg = <0x0 0x10020000 0x0 0x10000>;
+      clocks = <&clkgen JH7100_CLK_GMAC_ROOT_DIV>,
+               <&clkgen JH7100_CLK_GMAC_AHB>,
+               <&clkgen JH7100_CLK_GMAC_PTP_REF>,
+               <&clkgen JH7100_CLK_GMAC_GTX>,
+               <&clkgen JH7100_CLK_GMAC_TX_INV>;
+      clock-names = "stmmaceth", "pclk", "ptp_ref", "gtxc", "tx";
+      resets = <&rstgen JH7100_RSTN_GMAC_AHB>;
+      reset-names = "ahb";
+      interrupts = <6>, <7>;
+      interrupt-names = "macirq", "eth_wake_irq";
+      max-frame-size = <9000>;
+      phy-mode = "rgmii-txid";

This is unusual. Does your board have a really long RX clock line to
insert the 2ns delay needed on the RX side?

Just tested with "rgmii" and didn't notice any issues. If I'm not missing
anything, I'll do the change in the next revision.

rgmii-id is generally the value to be used. That indicates the board
needs 2ns delays adding by something, either the MAC or the PHY. And
then i always recommend the MAC driver does nothing, pass the value to
the PHY and let the PHY add the delays.

So try both rgmii and rgmii-id and do a lot of bi directional
transfers. Then look at the reported ethernet frame check sum error
counts, both local and the link peer. I would expect one setting gives
you lots of errors, and the other works much better.

I gave "rgmii-id" a try and it's not usable, I get too many errors. So 
"rgmii" should be the right choice here.

Thanks,
Cristian

     Andrew