net: enetc: restore RX ring congestion mode for ENETC v4

ENETC v4 has the same problem as ENETC v1: the RX BD ring congestion
mode (CM) is only configured in the phylink .mac_link_up() callback, so
it is cleared when enetc_reconfigure() rebuilds the RX BD rings at
runtime (for example when enabling or disabling PTP RX hardware
timestamping) without a link status change, and it is never restored.
As a result, the MAC can no longer generate PAUSE frames on ingress
congestion and flow control stops working.

Fix it in the same way as ENETC v1. Track the desired CM state in the
software flag ENETC_RXBDR_CM. Route enetc4_set_tx_pause() through the
shared helper enetc_set_congestion_mode(), which sets or clears the flag
according to tx_pause and updates the ENETC_RBMR_CM bit under si->gen_lock.
When the RX BD rings are (re)enabled, enetc_enable_rxbdr() consults this
flag and restores the CM bit accordingly, so flow control survives ring
reconfiguration even when the link status does not change.

Fixes: f5b9a1cde0a2 ("net: enetc: add PTP synchronization support for ENETC v4")
Signed-off-by: Wei Fang <wei.fang@nxp.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260821064140.1315611-3-wei.fang@oss.nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions