On 2024-11-29 23:29, Andrew Lunn wrote:
I was mistaken earlier; it is actually the EMAC that will introduce a time
skew by shifting the phase of the clock in 'rgmii' mode.
This is fine, but not the normal way we do this. The Linux preference
is that the PHY adds the delays. There are a few exceptions, boards
which have PHYs which cannot add delays. In that case the MAC adds the
delays. But this is pretty unusual.
After testing, it has been observed that modes other than 'rgmii' do not
function properly due to the current configuration sequence in the
driver code.
If you decided you want to be unusual and have the MAC add the delays,
it should not be hard coded. You need to look at phy-mode. Only add
Are you suggesting that 'rgmii' indicates the delay is introduced by the
board rather than the EMAC? But according to the
Documentation/devicetree/bindings/net/ethernet-controller.yaml, this
mode explicitly states that 'RX and TX delays are added by the MAC when
required'. That is indeed my preference.
delays for rgmii-id. And you then need to mask the value passed to the
PHY, pass PHY_INTERFACE_MODE_RGMII, not PHY_INTERFACE_MODE_RGMII_ID,
so the PHY does not add delays as well.
Andrew
--
Best Regards,
Yijie
