Re: [RFC PATCH v2 0/7] Add ethernet support for the Amlogic T7

[Lucas Tanure]

On Wed, Oct 7, 2026 at 2:01 PM Andrew Lunn <andrew@xxxxxxx> wrote:
>
> On Wed, Oct 07, 2026 at 09:26:20AM +0100, Lucas Tanure wrote:
> > The T7 pairs a Synopsys gigabit MAC with the same glue registers the
> > G12A has, but nothing described it. This adds the binding, the driver
> > support and the device tree nodes, and enables the port on the Khadas
> > VIM4.
> >
> > Unlike the G12A, the controller reaches DRAM through a pipeline stage
> > with a gate of its own, sys_ampipe_eth. Nothing else claims it, so
> > clk_disable_unused switches it off and transfers stop.
> >
> > v2 changes the RGMII delays, after review. phy-mode describes the
> > board, not which chip adds the delay, so this board is rgmii-id.
> > dwmac-meson8b did the opposite, and ignored the *-internal-delay-ps
> > properties. Patch 1 fixes that. The VIM4 needs it because the RTL8211F
> > transmit delay does not work here.
>
> What is special about the RTL8211F?
Maybe nothing, it may be this board. I cannot tell from here.

The RTL8211F does add the delays, the driver sets both bits and the
chip takes them. But when the RTL8211F adds the transmit delay, this
board gets no working link.

I measured the receive side by sweeping the MAC delay against the CRC
counter, with the PHY delay off and then on. The window moves by
about 2200ps, so the PHY receive delay is right.

Transmit is the problem. With the PHY doing TX the peer sees nothing
we send. With the MAC doing TX it runs at 935Mbit/s both ways with no
errors.

I asked Khadas about the board, no answer yet.
>
>      Andrew