Quectel EG91-E: Dormant Traffic Channel

[Sven Schwermer]

Hi,

We're observing an interesting behavior with the Quectel EG91-E modem 
(using QMI comms). Every now and then, we lose connectivity. When 
looking at the debug-level logs, we can see that the modem sends and 
indication with "Dormancy Status" set to "traffic-channel-dormant". This 
does not seem to happen when we artificially create more and continuous 
traffic on the cellular network interface. Following that indication, 
the modem appears to reset but does not re-enumerate on the USB. This 
makes all subsequent QMI transaction fail. How can this be explained? Is 
the modem misbehaving or should ModemManager/libqmi handle this somehow?

We're using mmcli 1.14.2 / qmicli 1.26.0. The modem's firmware is 
EG91EFBR06A04M4G. This is the relevant log excerpt:

15:34:14: [modem0] signal strength (lte): -80 dBm
15:34:14: [modem0] signal strength: -80 dBm --> 54%
15:34:14: [modem0] signal quality updated (54)
15:34:14: [modem0] periodic signal quality and access technology checks 
scheduled
15:34:21: [/dev/cdc-wdm0] received message...
           <<<<<< RAW:
           <<<<<<   length = 17
           <<<<<<   data   = 
01:10:00:80:01:14:04:E4:0B:01:00:04:00:18:01:00:01
15:34:21: [/dev/cdc-wdm0] received generic indication (translated)...
           <<<<<< QMUX:
           <<<<<<   length  = 16
           <<<<<<   flags   = 0x80
           <<<<<<   service = "wds"
           <<<<<<   client  = 20
           <<<<<< QMI:
           <<<<<<   flags       = "indication"
           <<<<<<   transaction = 3044
           <<<<<<   tlv_length  = 4
           <<<<<<   message     = "Event Report" (0x0001)
           <<<<<< TLV:
           <<<<<<   type       = "Dormancy Status" (0x18)
           <<<<<<   length     = 1
           <<<<<<   value      = 01
           <<<<<<   translated = traffic-channel-dormant
15:34:21: [modem0/bearer0] got QMI WDS event report
15:34:24: [modem0/ttyUSB0/qcdm] <-- 60 0a 00 9e 01 00 00 00 00 00 00 00 
00 ef ad 7e
15:34:24: [modem0/ttyUSB3/at] <-- '<CR><LF>RDY<CR><LF>'
15:34:24: [modem0/ttyUSB2/at] <-- '<CR><LF>RDY<CR><LF>'
15:34:24: [modem0/ttyUSB2/at] <-- '<CR><LF>+CFUN: 1<CR><LF>'
15:34:25: [modem0/ttyUSB2/at] <-- '<CR><LF>+CPIN: READY<CR><LF>'
15:34:25: [modem0/ttyUSB2/at] <-- '<CR><LF>+QUSIM: 1<CR><LF>'
15:34:25: [modem0] (quectel) checking SIM swap
15:34:25: [modem0] checking if SIM was swapped...
15:34:25: [modem0/sim0] loading SIM identifier...
15:34:25: [/dev/cdc-wdm0] sent message...
           <<<<<< RAW:
           <<<<<<   length = 33
           <<<<<<   data   = 
01:20:00:00:0B:01:00:06:00:20:00:14:00:03:04:00:00:00:00:00:02:05:00:E2:2F:02:00:3F:01:02:00:00:00
15:34:25: [/dev/cdc-wdm0] sent generic request (translated)...
           <<<<<< QMUX:
           <<<<<<   length  = 32
           <<<<<<   flags   = 0x00
           <<<<<<   service = "uim"
           <<<<<<   client  = 1
           <<<<<< QMI:
           <<<<<<   flags       = "none"
           <<<<<<   transaction = 6
           <<<<<<   tlv_length  = 20
           <<<<<<   message     = "Read Transparent" (0x0020)
           <<<<<< TLV:
           <<<<<<   type       = "Read Information" (0x03)
           <<<<<<   length     = 4
           <<<<<<   value      = 00:00:00:00
           <<<<<<   translated = [ offset = '0' length = '0' ]
           <<<<<< TLV:
           <<<<<<   type       = "File" (0x02)
           <<<<<<   length     = 5
           <<<<<<   value      = E2:2F:02:00:3F
           <<<<<<   translated = [ file_id = '12258' file_path = '{ [0] 
= '0 ' [1] = '63 '}' ]
           <<<<<< TLV:
           <<<<<<   type       = "Session" (0x01)
           <<<<<<   length     = 2
           <<<<<<   value      = 00:00
           <<<<<<   translated = [ session_type = 
'primary-gw-provisioning' application_identifier = '{}' ]
15:34:25: [modem0/ttyUSB2/at] <-- '<CR><LF>+QIND: SMS DONE<CR><LF>'
15:34:30: [modem0/ttyUSB2/at] <-- '<CR><LF>+QIND: PB DONE<CR><LF>'
15:34:35: transaction 0x6 aborted, but message is not abortable
15:34:35: [modem0] could not load SIM identifier: QMI operation failed: 
Transaction timed out (3 retries left)