Merge branch 'net-enetc-add-port-mdio-support-for-both-i-mx94-and-i-mx95'

Wei Fang says:

====================
net: enetc: add port MDIO support for both i.MX94 and i.MX95

The NETC IP has one external master MDIO interface (eMDIO) for managing
external PHYs, all ENETC ports share this eMDIO. The EMDIO function and
the ENETC port MDIO are the virtual ports of this eMDIO, ENETC can use
these virtual ports to access their PHYs. The difference is that EMDIO
function is a 'global port', it can access all the PHYs on the eMDIO, so
it provides a means for different software modules to share a single set
of MDIO signals to access their PHYs.

The ENETC port MDIO can only access its own external PHY. Furthermore,
its PHY address must be set to its corresponding LaBCR register in IERB
module, which is is a 64 KB size page containing registers that are used
for pre-boot initialization for all NETC PCIe functions. And this IERB
is owned by the host OS and it will be locked after the initialization,
so it cannot be configured at running time any more. The port MDIO can
only work properly when the PHY address accessed by it matches the value
of its corresponding LaBCR[MDIO_PHYAD_PRTAD]. Otherwise, the MDIO access
by the port MDIO will not take effect.

Note that the same PHY is either controlled by port MDIO or by the EMDIO
function. The netc-blk-ctrl driver will only set the PHY address in the
LaBCR register corresponding to the ENETC when the ENETC node contains
an mdio child node, and the ENETC driver will only create the port MDIO
bus then. An example in DTS is as follows, the EMDIO function will not\
access this PHY.

enetc_port0 {
phy-handle = <&ethphy0>;
phy-mode = "rgmii-id";

mdio {
#address-cells = <1>;
#size-cells = <0>;

ethphy0: ethernet-phy@1 {
reg = <1>;
};
};
};

If users want to use EMDIO funtion to manage the PHY, they only need to
place the PHY node in the emdio node. The same PHY must not be placed
simultaneously within the ENETC node. An example in DTS to use EMDIO
is as below.

netc_emdio {
ethphy0: ethernet-phy@1 {
reg = <1>;
};

ethphy2: ethernet-phy@8 {
reg = <8>;
};
};

In the host OS, when there are multiple ENETCs, they can all access their
PHYs using their own port MDIO, or they can all access their PHYs using
the EMDIO function, or they can partially use port MDIO and partially use
the EMDIO function.

Another typical use case of port MDIO is the Jailhouse usage. An ENETC is
assigned to a guest OS. The EMDIO function will be unavailable in the
guest OS because EMDIO is controlled by the host OS. Therefore, the ENETC
can use its port MDIO to manage its external PHY in this situation. In
this use case, the host OS's root dtb will disable the ENETC node, so the
host OS's ENETC driver will not probe the ENETC and its PHY.

In addition, this series also adds the internal MDIO bus support, each
ENETC has an internal MDIO interface for managing on-die PHY (PCS) if it
has PCS layer.
====================

Link: https://patch.msgid.link/20251119102557.1041881-1-wei.fang@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>