ap: switch 5GHz driver to out-of-tree morrownr/rtw89 for USB3 support

The in-kernel rtw89_8852bu on this Ubuntu kernel base predates mainline's
USB2->3 auto-switch for this chip, permanently capping the AP dongle at
USB2/480M. morrownr/rtw89 (dkms) has that switch. ap/rtw89.conf now
blacklists the in-kernel rtw89 modules and tunes the replacement
(disable_ps_mode + switch_usb_mode); ap/install-rtw89-driver.sh builds
and installs it, pinned to a specific upstream commit, kept separate
from deploy.sh since a dkms rebuild is too slow to run on every deploy.

Verified live: negotiates USB3/5000M on a dedicated USB3 controller
(480M on a USB2-only one, as expected), AP recovered via hostapd's
Restart=always + van-ap-watchdog with no manual intervention. Hit and
documented one real gotcha along the way: in-kernel rtw89_core refused
to unload while its own dependents (rtw89_8852b, rtw89_8852b_common)
were still loaded, which blocked the new module with a duplicate-symbol
error until all in-kernel modules were removed first.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YJfEELeh3ercpRBp8yYrYS

README.md

@@ -92,7 +92,7 @@ This directory is the source of truth. The live system files live under `/etc`,
 | `nftables.conf` | `/etc/nftables.conf` | NAT: `masquerade ip saddr 10.42.0.0/24 oifname != br0` → follows whatever WAN is active |
 | `99-van-router.conf` | `/etc/sysctl.d/99-van-router.conf` | `net.ipv4.ip_forward=1` |
 | `regdomain.service` | `/etc/systemd/system/regdomain.service` | `iw reg set CA` at boot, before NetworkManager |
-| `rtw89.conf` | `/etc/modprobe.d/rtw89.conf` | `options rtw89_core disable_ps_mode=Y` (else AP drops beacon when idle) |
+| `rtw89.conf` | `/etc/modprobe.d/rtw89.conf` | 5GHz dongle: `disable_ps_mode=Y` (else AP drops beacon when idle) + blacklists in-kernel rtw89 so the out-of-tree morrownr/rtw89 dkms driver (installed separately, not by deploy.sh) loads instead — see gotchas below |
 | `rtw88.conf` | `/etc/modprobe.d/rtw88.conf` | 2.4GHz dongle: `disable_lps_deep=Y` (same PS reasoning) + `switch_usb_mode=N` (don't self-upgrade to USB3 — it radiates into 2.4GHz) |
 
 ### `failover/` — multi-WAN
@@ -366,7 +366,8 @@ Four things `deploy.sh` does **not** do (one-time, manual):
 
 - **AP on hostapd, not NetworkManager.** NM's hotspot caps the rtw89 radio at HT20/20MHz; hostapd gives the full VHT80/HE (WiFi-6). The AP iface is therefore NM-*unmanaged*; networkd gives it its static IP.
 - **`rtw89` power-save must be off** (`disable_ps_mode=Y`) or the AP stops beaconing when idle and the SSID vanishes.
-- **RTL8852BU is USB-2.0 and hangs under load if it shares a USB hub.** Keep the AP dongle on its **own** USB controller, separate from the WAN ethernet. Symptom of a shared bus: `c2h reg timeout` + `Polling beacon packet empty fail` under throughput, SSID drops. (`timed out to flush queues` alone is benign.)
+- **RTL8852BU is USB-2.0 and hangs under load if it shares a USB hub.** Keep the AP dongle on its **own** USB controller, separate from the WAN ethernet. Symptom of a shared bus: `c2h reg timeout` + `Polling beacon packet empty fail` under throughput, SSID drops. (`timed out to flush queues` alone is benign.) True regardless of which driver (in-kernel or out-of-tree) is bound — it's a physical bus-bandwidth issue, not a driver bug.
+- **5GHz dongle runs the out-of-tree `morrownr/rtw89` driver (since 2026-08-23), not the in-kernel one.** This Ubuntu kernel base (`7.0.0-1017-raspi`) predates mainline's rtw89 USB2→3 auto-switch, so the in-kernel driver permanently caps the 8852BU at USB2/480M. The out-of-tree driver has that switch (`switch_usb_mode=y` in `ap/rtw89.conf`) and needs a real USB3-capable port to actually benefit from it — a USB2-only port still caps it regardless of driver (confirmed live: 480M on a USB2-only controller, 5000M/SuperSpeed after moving to a dedicated USB3 controller). Driver itself logs `"2.4 GHz performance may be better in a USB 2 port"` on load — watch the 2.4GHz radio for new interference now that 5GHz runs SuperSpeed signalling nearby. Installed/updated via `sudo ./ap/install-rtw89-driver.sh` (pins a specific upstream commit, `dkms install`, `make install_fw`) — **not** run automatically by `deploy.sh`, since a dkms rebuild is slow and shouldn't fire on every routine deploy; run it manually after a fresh Pi provisioning or to bump the pin. DKMS itself auto-rebuilds across kernel upgrades. Module names get a `_git` suffix (`rtw89_8852bu_git` etc.) — `ap/rtw89.conf`'s blacklist stops the in-kernel modules from claiming the device instead. **Gotcha hit switching a live system over**: the in-kernel `rtw89_core` won't unload while its own in-kernel dependents (`rtw89_8852b`, `rtw89_8852b_common`) are still loaded — remove all of them first or the out-of-tree module fails to load (`exports duplicate symbol`). The install script's own output has the exact recovery steps.
 - **van-failover changes metrics via `ip route`, never `nmcli device reapply`.** `reapply` **resets the r8152 USB-ethernet carrier**, which caused a ~10s-ping-drop flapping feedback loop. Pure `ip route` changes are carrier-safe.
 - **Disable EEE on USB ethernet** (`50-disable-eee` dispatcher) — its idle power-save parks the *backup* WAN link and breaks health probes.
 - **Per-WAN probing needs `curl --interface if!<dev>`** (forces `SO_BINDTODEVICE`); plain `--interface <name>` only sets the source IP and still routes via the default WAN. `rp_filter` is loose (`2`), required for this.