Re: [MM] [PATCH] iface-modem, novatel-lte: disable network scan in LTE mode

[Ben Chan <benchan chromium org>]

On Thu, Jan 3, 2013 at 1:37 PM, Aleksander Morgado <aleksander lanedo com> wrote:

>     > Also, based on my experiments, the modem sometimes seems to hang when
>     > running AT+COPS=?. This patch avoids AT+COPS=? from being issued when
>     > the modem is in LTE mdoe.
>
>     From what I can see, it also avoids the Scan when the access tech is
>     unknown:
>
>     +    if ((access_tech == MM_MODEM_ACCESS_TECHNOLOGY_UNKNOWN) ||
>     +        (access_tech & MM_MODEM_ACCESS_TECHNOLOGY_LTE)) {
>
>     So you're really limiting the scanning for networks only to when the
>     modem is already connected to a given network which is not LTE. I don't
>     think we shouldn't ban from scanning when access tech is UNKNOWN.
>
>
> I include UNKNOWN just to be safe as there may be a period of time when
> the access technology is not yet determined.
>

That's what I mean; it should be perfectly valid to be able to scan for
networks when the modem is not yet registered anywhere, i.e. when the
access tech is unknown.

Let me remove the check for unknown access technology.

 

>     Also, the reply to AT+COPS=? may really take a loong time; you sure it
>     gets stuck?
>
>
> From what I've seen before, the scan operation timed out and the modem
> didn't respond to AT commands anymore. However, that's not frequently
> reproducible.
>

So this patch is just avoiding the need to parse an empty list as the
AT+COPS=? command replies just OK by default when in LTE mode. Is it
really worth the complication of subclassing the scan method just to
avoid that? :-/

The only purpose of this patch is to skip "AT+COPS=?" in LTE mode as that causes the modem to sometimes behave weirdly :-/

 

>
>     I wonder how the scan works when the Novatel LTE modem is handled by the
>     QMI driver. IIRC Dan said we wouldn't need this specific plugin any more
>     once the modem is handled by the QMI implementation.
>
>
> I haven't tried the QMI driver for this modem, but wonder if it behaves
> in a similar way as the limitation is most likely a firmware issue.
>

It would be great if you could check the overall behaviour of the
Novatel LTE modem with the QMI driver, to see if there is any reason not
to switch to it...

Will do

 

--
Aleksander