On Sun, Jun 13, 2021 at 04:34:52PM +0800, 周琰杰 wrote:

于 Thu, 10 Jun 2021 16:57:29 +0200
Andrew Lunn [off-list ref] 写道:

quoted

quoted

Here is Ingenic's reply, the time length corresponding to a unit is
19.5ps (19500fs).  

Sometimes, there is a negative offset in the delays. So a delay value
of 0 written to the register actually means -200ps or something.

Ah, perhaps this explains why we still need to add fine-tuning
parameter in rgmii-id and rgmii-txid modes to ensure that the network
works properly.

Please try to find this out. rgmii means no delay. If the hardware is
doing -500pS by default, you need to take this into account, and add
the 500pS back on.

    Andrew