MS-TEAMS breaks NCM in trunk. Debugging help needed

Installing and Using OpenWrt
1

I use the BT Home Hub 5a (Lantiq xrx200 soc) with trunk built myself. I have few installations in place for years.

My brother has one. His internet is wireless from the mobile phone network via a Huawei USB modem (E3272s-153) which presents as an NCM interface and 2 x USBTTY ports. It has worked fine for ages, streaming movies and sports but never MS-TEAMS. Two weeks back, he was obliged to give a lecture from home via MS-TEAMS to a group of 25+ students as a result of covid-19 restrictions.

The bthhta rebooted 3 times during the 90min lecture causing mayhem. The following day I was present when he began a second lecture. Internet was lost on the LAN after 20 mins. According to Luci, the WAN was up and the huawei modem indicated an LTE connection throughout. Syslog and dmesg showed no errors. I had to rip out the bthh5a and use a commercial product so my bother could continue working.

The build of trunk in use was from Sept 12th last and it is minimal (no xDSL nor ath10k firmware included) and no frills software.

I need advise of how to debug this issue before I try to simulate similar conditions (I know nothing of teams). How do I force the NCM subsystem to be much more verbose in syslog. Any hints and advice hugely appreciated.

2

Looks like a power and/or heating issue on a high load. I suggest to get a better modem.
In the mean time check if you can use more powerful power supply or provide additional power to the modem by using USB Y-cable.

3

I have at least three of that model huawei modem out there for the past two years. Only TEAMs breaks the setup. I have continued to use my brothers bthh5a and the same huawei in my home for the past 10 days and multiple clients without any issues.

I do not see how you conclude it is a power/heating issue. If the modem locked up and stopped communication, I expect syslog/dmesg to say something.

4

Is the computer on wifi?

5

@h8red: yes, on the 2.4GHz AP. If the modem hangs, and there is no clear sign it did (nothing in syslog), why would the router reboot?

I'm really looking for verbose debugging.

6

Could be the same issue. Rebuild latest trunk. My advice

8

Huawei E3272/3276 are known to be power hungry, so cables and power are always #1 on my checklist. Your problems could be caused by other factors though. At the same time I recommend to use a short USB cable between modem and router, plugging modem directly is not always good.

9

@h8red: Thank you. That might well explain it. However, I would really like more verbose debugging before testing it in a live MS-TEAMS meeting.

10

@AndrewZ, thank you for this. I had the modem in the usb port.

11

@h8red, your suggestion is looking good. I've run a mini TEAMS meeting using trunk built today without a problem for 2 hours. The Sept build of trunk causes a reboot after ~30 mins. I greatly appreciate your assistance. Very many thanks!

12

@h8red, well it stayed up 24 hours with a mini MS-TEAMS meeting running. However, the kernel log shows this:

[   71.035332] usb 1-1: new high-speed USB device number 2 using dwc2
[   71.253955] usb 1-1: New USB device found, idVendor=12d1, idProduct=14fe, bcdDevice= 1.02
[   71.261500] usb 1-1: New USB device strings: Mfr=3, Product=2, SerialNumber=5
[   71.268372] usb 1-1: Product: HUAWEI Mobile
[   71.272563] usb 1-1: Manufacturer: HUAWEI Technology
[   71.277677] usb 1-1: SerialNumber: FFFFFFFFFFFFFFFF
[   71.295398] usb-storage 1-1:1.0: USB Mass Storage device detected
[   71.317130] scsi host0: usb-storage 1-1:1.0
[   72.181224] dwc2 1e101000.usb: Not connected
[   72.420302] usb 1-1: USB disconnect, device number 2
[   72.814961] usb 1-1: new high-speed USB device number 3 using dwc2
[   73.031839] usb 1-1: New USB device found, idVendor=12d1, idProduct=1506, bcdDevice= 1.02
[   73.038843] usb 1-1: New USB device strings: Mfr=3, Product=2, SerialNumber=0
[   73.046238] usb 1-1: Product: HUAWEI Mobile
[   73.050225] usb 1-1: Manufacturer: HUAWEI Technology
[   73.121298] option 1-1:1.0: GSM modem (1-port) converter detected
[   73.131039] usb 1-1: GSM modem (1-port) converter now attached to ttyUSB0
[   73.142162] option 1-1:1.1: GSM modem (1-port) converter detected
[   73.149561] usb 1-1: GSM modem (1-port) converter now attached to ttyUSB1
[   73.197931] huawei_cdc_ncm 1-1:1.2: MAC-Address: 0c:5b:8f:27:9a:64
[   73.203036] huawei_cdc_ncm 1-1:1.2: setting rx_max = 16384
[   73.218931] huawei_cdc_ncm 1-1:1.2: setting tx_max = 16384
[   73.223849] huawei_cdc_ncm 1-1:1.2: NDP will be placed at end of frame for this device.
[   73.243577] huawei_cdc_ncm 1-1:1.2: cdc-wdm0: USB WDM device
[   73.261064] huawei_cdc_ncm 1-1:1.2 wwan0: register 'huawei_cdc_ncm' at usb-1e101000.usb-1, Huawei CDC NCM device, 0c:5b:8f:27:9a:64
[   73.273832] usb-storage 1-1:1.3: USB Mass Storage device detected
[   73.310183] scsi host0: usb-storage 1-1:1.3
[   73.320251] usb-storage 1-1:1.4: USB Mass Storage device detected
[   73.367113] scsi host1: usb-storage 1-1:1.4
[   74.375724] scsi 0:0:0:0: CD-ROM            HUAWEI   Mass Storage     2.31 PQ: 0 ANSI: 2
[   74.416536] scsi 1:0:0:0: Direct-Access     HUAWEI   TF CARD Storage  2.31 PQ: 0 ANSI: 2
[   74.529404] sd 1:0:0:0: [sda] Attached SCSI removable disk
[   89.064278] BUG: spinlock wrong CPU on CPU#0, block/3343
[   89.069098]  lock: ebu_lock+0x0/0x20, .magic: dead4ead, .owner: block/3343, .owner_cpu: 1
[   89.077346] CPU: 0 PID: 3343 Comm: block Not tainted 5.4.72 #0
[   89.082176] Stack : 81110000 00000000 80890000 81130000 809229d4 84adf944 00000000 00000000
[   89.090527]         80b10000 8750f42c 8097a74f 808a2a28 00000000 00000001 84adf8e8 3c829635
[   89.098878]         00000000 00000000 81150000 00000000 00000030 00000000 352e342e 37322023
[   89.107230]         00000177 28800000 00000000 00012e22 80000000 00000000 00000001 809c0000
[   89.115585]         87d67c00 00000200 84ae8c00 00000000 00000001 00000010 00000000 80b10000
[   89.123942]         ...
[   89.126375] Call Trace:
[   89.128842] [<800108c0>] show_stack+0x30/0x100
[   89.133301] [<806b8dd0>] dump_stack+0xe4/0x158
[   89.137731] [<800a1288>] do_raw_spin_unlock+0xf8/0x100
[   89.142874] [<806ddc20>] _raw_spin_unlock_irqrestore+0x30/0x94
[   89.148701] [<80457ae8>] nand_read_oob+0x378/0x740
[   89.153482] [<8043f568>] part_read_oob+0x50/0xa8
[   89.158093] [<8043c4d8>] mtd_read_oob+0x60/0x100
[   89.162701] [<8043c5b4>] mtd_read+0x3c/0x54
[   89.166890] [<80446ecc>] mtdblock_readsect+0x58/0x17c
[   89.171930] [<804467a4>] mtd_queue_rq+0x424/0x5c4
[   89.176640] [<8033fc60>] __blk_mq_try_issue_directly+0x140/0x204
[   89.182635] [<80341910>] blk_mq_request_issue_directly+0x44/0x70
[   89.188645] [<80341994>] blk_mq_try_issue_list_directly+0x58/0xf4
[   89.194743] [<803472e0>] blk_mq_sched_insert_requests+0x16c/0x3b4
[   89.200828] [<80341688>] blk_mq_flush_plug_list+0x1f8/0x43c
[   89.206408] [<803344f4>] blk_flush_plug_list+0xc4/0xe8
[   89.211535] [<80334540>] blk_finish_plug+0x28/0x3c
[   89.216321] [<8017e0d8>] read_pages+0x78/0x168
[   89.220758] [<8017e458>] __do_page_cache_readahead+0x290/0x2d8
[   89.226607] [<80170e2c>] generic_file_read_iter+0x7b4/0xddc
[   89.232171] [<801f2fc4>] __vfs_read+0x198/0x1ec
[   89.236686] [<801f30b8>] vfs_read+0xa0/0x154
[   89.240952] [<801f33f4>] ksys_read+0x64/0x10c
[   89.245315] [<8001a270>] syscall_common+0x34/0x58