Re: [PATCH net-next 2/2] net: stmmac: Add Siflower SF19A2890 glue

[Joseph Telaak]

> What does SF19A2890_GMAC_RX_DELAY_EN do? By default rx is 0, so the
> delay is not enabled. Is that any different to actually enabling it
> with SF19A2890_GMAC_RX_DELAY set to 0?

RX_DELAY_EN switches the RX delay line in; with it clear the line is
bypassed. I checked on the board: with it clear, the link passes
traffic at every RX_DELAY value, including 40 and 80 steps, which fail
with it set; with it set, RX_DELAY applies as measured in the sweep.

With RX_DELAY at 0, enabled and bypassed both pass traffic, so any
difference between them is too small to show at 1000 Mb/s. v2 will
explain this in a comment.