Quectel EG91-E: Dormant Traffic Channel

[Sven Schwermer]

Hi Aleksander,

Thanks for the pointers. We'll try to get in touch with Quectel.

Sven

On 9/5/22 19:19, Aleksander Morgado wrote:
> Hey,
> 
>> 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
> 
> The traffic dormant messages are usually expected when there is no
> data traffic going through the modem, they should not have any major
> impact anywhere.
> 
>> 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>'
> 
> This totally looks like a modem internal self-reset, something to
> report to Quectel. The device doesn´t go away from USB, but internally
> the whole radio stack was likely fully reseted.
> See https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/issues/285
> 
>