Laguna: bridge and management port fixes

[troglobit]

Description

Fixes and debug aids for the Laguna (LAN969x) boards, found while bringing the Tactical 1000 into the new test system.

Kernel, synced from kkit-linux-6.18.y:

• Bridge IP address unreachable (patches 0082–0084). Every bridge test on the Tactical rig failed on this. The driver stands in hardware VLAN 1 for a VLAN-unaware bridge, and confd creates bridges with vlan_default_pvid 0, which adds VLAN 1 at creation and removes it right after. That forgot the VID 1 broadcast entry, so ARP from the ports never reached the CPU, and the bridge MAC entry, so unicast to the bridge was flooded to the ports. A third fix stops the driver from forgetting a bridged port's MAC on link down, which cut the bridge off whenever its first port, whose MAC the bridge uses, was disabled. Traced with symreg on the EV23X71A.
• Management port "lockups" (patch 0081). All standalone ports share pvid 0, so they share the MAC table entry that delivers a multicast group to the CPU, but the driver forgot it on behalf of a single port. Taking any other standalone port down, or adding it to a bridge, removed the all-nodes and mDNS entries the management port relies on. Frames were received but never forwarded to the CPU, so the unit dropped out of ixll and the test rig until the port was cycled. Fixed by reference counting the shared entries.
• Scheduling while atomic in the same path (patch 0079): ndo_set_rx_mode runs under netif_addr_lock_bh, and the MAC table access took a mutex. Now a spinlock with an atomic poll, as lan966x does. Upstream fixed it via the new ndo_set_rx_mode_async, which 6.18 does not have.
• symreg debugfs driver from Microchip's BSP (patch 0080), for register access by name.

Infix side:

• PTP ports kept going FAULTY on the copper ports, which failed every PTP test on the rig. The LAN8814 PHYs ask to be the default timestamp provider and the kernel grants it, so each port timestamps with its quad PHY's clock instead of the switch core's. On the EV23X71A the PHY's TX timestamp arrives over MDIO later than the 10 ms ptp4l allows; on the Tactical 1000 it never arrives. confd now selects the PTP clock of the interface's own device, the switch core on Laguna, for every port of an instance, and allows 100 ms for hardware timestamps for boards that only have a PHY clock. One clock for all ports is also what boundary and transparent clocks and the TSN schedules need. Verified on the EV23X71A and on alpha in the rig: no faults, switch PTP interrupts delivering the timestamps.
• symreg package, selected by the Laguna boards, with the device tree node in each board's Infix overlay. Usage notes, including how to chase a port fault, in board/aarch64/microchip-lan969x/README.md.
• aarch64_minimal_defconfig lacked the Tactical 1000, EV23X71A and Vero W6m board packages, so PR CI images had no DTB for them and hung after Starting kernel ....
• provision-tactical did not seed uboot.env, so RAUC could not read any boot state on provisioned units.
• kernel-refresh.sh deleted the patch directory it had just regenerated when run for the current kernel version.
• log and follow moved to /etc/profile.d/, so they work in BusyBox ash on minimal builds too.

Risk analysis

Bridge fixes (0082–0084): the VID 1 broadcast entry is now permanent, like the VID 0 one for standalone ports. Standalone ports never classify to VID 1 and PGID_BCAST holds only bridged ports, so it is inert without a bridge. The shared-entry count only covers entries the driver installed itself (locked); auto-learned entries behave as before. Skipping learn and forget on up/down for bridged ports leaves those entries to the bridge FDB notifications the driver already handles; join still forgets the standalone entry and leave still restores it. Upstream has the same three bugs, hidden by the default vlan_default_pvid 1.

Lock conversion (0079): nothing sleeps or takes another lock under sparx5->lock, it nests inside the mutexes and never the reverse, and every caller is process context; the atomic switchdev notifier defers FDB work and never touches the MAC table. A softirq caller would already have been taking a mutex from softirq, so the spinlock tolerates exactly the contexts the mutex had to. Same fix lan966x took in 77bdaf39f3c8. Only behaviour change: a wedged MAC table command busy-waits up to 100 ms instead of sleeping.

Multicast fix (0081): list touched only on group join and leave, held across the hardware learn/forget so two ports cannot race on the same entry. Lock order is always mc_cpu_lock then sparx5->lock. Unicast addresses learned per port have the same shape if two standalone ports share a MAC; left for a follow-up, and not a configuration Infix produces.

symreg: debugfs only, root only; the driver never probes without its device tree node, so it is inert on non-Laguna boards. The tool bypasses the driver when writing, documented in the README.

Checklist

Tick relevant boxes, this PR is-a or has-a:

• Bugfix
  • Regression tests
  • ChangeLog updates (for next release)
• Feature
  • YANG model change => revision updated?
  • Regression tests added?
  • ChangeLog updates (for next release)
  • Documentation added?
• Test changes
  • Checked in changed Readme.adoc (make test-spec)
  • Added new test to group Readme.adoc and yaml file
• Code style update (formatting, renaming)
• Refactoring (please detail in commit messages)
• Build related changes
• Documentation content changes
  • ChangeLog updated (for major changes)
• Other (please describe): debug tooling (symreg)

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