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

[Ben Chan <benchan chromium org>]

On Thu, Jan 3, 2013 at 1:17 PM, Aleksander Morgado <aleksander lanedo com> wrote:

On 03/01/13 20:13, Ben Chan 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.

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.

 

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.

 

--
Aleksander