Symptom

An access point crashes continuously immediately after booting. The console shows errors similar to the following: misc sia: Failed to get good reading [ ... ] NMI watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [ ... ] CPU: 1 PID: 3611 Comm: insmod Tainted: P O 4.1.52 #5 Hardware name: Broadcom-v8A (DT) task: ffffffc0744ede00 ti: ffffffc027374000 task.ti: ffffffc027374000 PC is at sia_touch_bit+0x174/0x190 [sia_driver] LR is at sia_touch_bit+0x124/0x190 [sia_driver] [ ... ] Rebooting in 5 seconds.. Other PC/LR values that may be seen include: PC is at usDelay+0x18/0x40 [sia_driver] LR is at sia_touch_bit+0x7c/0xb8 [sia_driver] PC is at sia_read_from_device+0x94/0x370 [sia_driver] LR is at sia_read_from_device+0x7c/0x370 [sia_driver]

Conditions

This behavior is seen under the following conditions: * Access point is a model that supports Self-Identifying Antennas (SIA), such as C9120AXE, C9130AXE, IW9167EH * Access point is loaded with code that supports SIA (i.e. 17.5.1 or above, not 8.9 or earlier) * Crash can also be seen with 8.10.x code. * Antenna is an SIA capable model, such as AIR-ANT2524V4C-RS= * Antenna's EEPROM has corrupt or unprogrammed data (for example, due to the CSCwh16439 manufacturing problem with AIR-ANT2524V4C-RS=)

Workaround

For an SIA that uses RP-TNC cables to connect to the AP's antenna terminals, such as the AIR-ANT2524V4C-RS=, a partial workaround is to attach the violet-banded antenna cable to any one of the orange-banded RP-TNC terminals (i.e. to terminal B, C or D), but NOT to the violet-banded terminal A. This will prevent the antenna from self-identifying, and so will prevent the AP from crashing, and will allow configuring the antennas for their actual gain. For full SIA functionality, the affected antenna must be repaired or replaced.

Further Problem Description