RE: [PATCH v4 net-next 03/15] net: enetc: add link status message support to PF driver

NXP Confidential

-----Original Message-----
From: Wei Fang (OSS) <redacted>
Sent: Wednesday, September 9, 2026 1:07 PM

[...]

Subject: [PATCH v4 net-next 03/15] net: enetc: add link status message support
to PF driver

From: Wei Fang <wei.fang@nxp.com>

Add a mechanism for VFs to learn the PF link state, using message class
0x80 (ENETC_MSG_CLASS_ID_LINK_STATUS) with three VSI-to-PSI commands:

1. ENETC_MSG_GET_CURRENT_LINK_STATUS: the VF queries the current PF link
   status synchronously. This is intended for DPDK-owned VFs and is not
   used by the Linux VF driver.
2. ENETC_MSG_REGISTER_LINK_CHANGE_NOTIFIER: the VF registers for link
   change notification. The PF then reports the current link status and
   notifies the VF on every later link change.
3. ENETC_MSG_UNREGISTER_LINK_CHANGE_NOTIFIER: the VF unregisters.

The PSI-to-VSI notification is 16 bits wide: the upper 8 bits carry the
class ID and the lower 8 bits the class code. Bit 0 of the class code
indicates the link state (1 = down, 0 = up) and bit 1 indicates whether
TX PAUSE is enabled on the PF. The TX PAUSE state is included so a VF
can decide whether to enable congestion mode on its RX BD rings, which
only works when the PF can actually send PAUSE frames.

Notifications are sent through the ENETC_PSIMSGSR register. Since sending
a notification may take a long time, as it polls the per-VF message
status bits, the actual transmission is deferred to an ordered workqueue
rather than running in the phylink link_up/link_down callbacks. The
link_status_ms_mask tracks the VFs registered for notification and is
cleared when SR-IOV is disabled.

Export enetc_pf_notify_vf_link_up() and enetc_pf_notify_vf_link_down()
for the PF phylink callbacks. Through this, VFs can perceive the link
status and report it to upper layers such as the kernel network stack,
containers and virtual machines.

Currently only the ENETC v4 driver supports this feature; v1 does not.
And the SR-IOV feature of ENETC v4 will be added by subsequent patches.

Signed-off-by: Wei Fang <wei.fang@nxp.com>

Reviewed-by: Claudiu Manoil <claudiu.manoil@nxp.com>