On Mon, Jul 6, 2020 at 6:12 AM Andre Przywara andre.przywara@arm.com wrote:
When sending a command via the MDIO bus, the Designware MAC expects some bits in the CMD register to describe the clock divider value between the main clock and the MDIO clock. So far we were omitting these bits, resulting in setting "00", which means "/ 16", so ending up with an MDIO frequency of either 18.75 or 12.5 MHz. All the internal PHYs in the H3/H5/H6 SoCs as well as the Gbit Realtek PHYs seem to be fine with that - although it looks like to be severly overclocked (the MDIO spec limits the frequency to 2.5 MHz). However the external 100Mbit PHY on the Pine64 (non-plus) board is not happy with that, Ethernet was actually never working there, as the PHY didn't probe.
How come the existing divider cannot work with 100Mbit external PHY(assuming external regulator pin as properly enabled) since it works with 1Gbit already?
Jagan.