Hi Aleksander,
On 18/08/2020 5:43 pm, Aleksander Morgado wrote:
On Tue, Aug 18, 2020 at 8:16 AM Brendan Simon (eTRIX)
<brendan.si...@etrix.com.au> wrote:
I'm using a Quectel EC21 modem on a Debian Buster Linux system (using
modemmanager 1.10.0).
Please note, MM 1.10.0 is a very very old release, no longer
supported, and it's not even the last one inthe 1.10.x series...
Fair enough, but 1.10.0 is comes with Debian Buster, which is the latest
Stable release of Debian. However there is a backport of 1.14, from the
Unstable (next release) distro, for Buster.
I want to force it to one of 3G or 4G to stop it changing/swapping between the
two.
I've tried using the `mmcli -m 0 --set-allowed-modes=3g
`. mmcli seems happy with that.
However, some time later it swaps over to 4G (lte)
--------------------------------
Status | lock: sim-pin2
| unlock retries: sim-pin (3), sim-pin2 (3), sim-puk (10),
sim-puk2 (10)
| state: connected
| power state: on
| access tech: lte <<< 4G !!!
| signal quality: 63% (recent)
--------------------------------
Have I got the right expectations of the `--set-allowable-modes` feature?
Is there something else I need to do?
This may be a known issue with QMI modems where the internal network
registration attempt is done with "QMI NAS Register In Network"; this
command not only registers in network, it also makes the access tech
preference fallback to "any", and MM doesn't consider that in its API.
There is a recent patch to avoid this, by avoiding the use of "NAS
Register in Network" and use "NAS Set System Selection Preference"
instead:
https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/commit/c70b3557184fdf1472ff0cb36e9fd937cc7f9024
That patch is not yet in any release, though, not even in 1.14.0. I'll
backport it to the 1.14.x branch so that it gets into 1.14.2.
You can confirm that this issue is happening to you by running this
command once the tech went back to the one you didn't want:
$ qmicli -d /dev/cdc-wdm0 -p --nas-get-system-selection-preference
Here is the output.
# qmicli -d /dev/cdc-wdm0 -p --nas-get-system-selection-preference
[/dev/cdc-wdm0] Successfully got system selection preference
Emergency mode: 'no'
Mode preference: 'umts, lte'
Band preference: 'wcdma-2100, wcdma-850-us'
LTE band preference: '1, 3, 5, 7, 28'
TD-SCDMA band preference: '(null)'
Roaming preference: 'any'
Network selection preference: 'automatic'
Service domain preference: 'cs-ps'
GSM/WCDMA acquisition order preference: 'wcdma'
Acquisition order preference: lte, umts, gsm, td-scdma,
cdma-1x, cdma-1xevdo
What are the key indicators that confirm the issue?
Network selection preference: 'automatic'???
Acquisition order preference: lte, umts, gsm, td-scdma,
cdma-1x, cdma-1xevdo???
Hopefully 1.14.2 is not far away and hopefully it will be backported for
Debian Buster quickly :)
Thanks, Brendan.
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