[PATCH v2 net 0/2] net: enetc: restore RX ring congestion mode after ring reconfiguration

[wei . fang]

From: Wei Fang <wei.fang@xxxxxxx>

The RX BD ring congestion mode (CM) enables the ENETC MAC to generate
PAUSE frames when ingress congestion occurs. It is configured only in
the phylink .mac_link_up() callback, which is invoked when the link
status changes.

However, enetc_reconfigure() tears down and re-creates the RX BD rings
at runtime without any link status change, for example when enabling or
disabling PTP RX hardware timestamping. enetc_setup_rxbdr() rebuilds the
RBMR register from zero, which clears the CM bit, and since the link
status does not change, .mac_link_up() is not called again to restore
it. As a result, flow control silently stops working after such a
reconfiguration.

To solve this issue, track the desired CM state in a software flag
ENETC_RXBDR_CM, which is maintained by the .mac_link_up() /
.mac_link_down() callbacks and consulted by enetc_setup_rxbdr() when the
RX BD rings are (re)configured. Both ENETC v1 and ENETC v4 are affected
and are fixed in the same way.

---
v2:
1. Add a generic helper enetc_set_congestion_mode() to set the
   congestion mode of the SI's RX BD rings
2. Move the setting of ENETC_RBMR from enetc_setup_rxbdr() to
   enetc_enable_rxbdr()
3. Add gen_lock to struct enetc_si to prevent concurrent access to
   ENETC_RBMR and the ENETC_RXBDR_CM bit of priv->flags
v1 link: https://lore.kernel.org/imx/20260728023217.2499420-1-wei.fang@xxxxxxxxxxx/
---

Wei Fang (2):
  net: enetc: restore RX ring congestion mode after ring reconfiguration
  net: enetc: restore RX ring congestion mode for ENETC v4

 drivers/net/ethernet/freescale/enetc/enetc.c  | 72 +++++++++++++++----
 drivers/net/ethernet/freescale/enetc/enetc.h  |  9 +++
 .../net/ethernet/freescale/enetc/enetc4_pf.c  | 16 ++---
 .../net/ethernet/freescale/enetc/enetc_pf.c   | 14 +---
 4 files changed, 72 insertions(+), 39 deletions(-)

-- 
2.34.1