Hi Giancinto,

Den tis 18 feb. 2020 kl 20:27 skrev Giacinto Cifelli <gciofono@gmail.com>:
Hi Richard,

On Tue, Feb 18, 2020 at 10:19 AM Richard Röjfors
<richard.rojfors@gmail.com> wrote:
>
> Hi,
>
> Ofono (at least for ublox) is always powering off the radio during start.
> This can of course be handy of programmatic reasons to bring the modem to a known state.
> Some configuration requires the radio to be turned off;  for instance the LTE auto connect APN. But on the other hand these are stored in non-volatile memory and could be configured before hand.
>
> The big drawback with turning it off is that it might take time to register again when the radio is on. I have seen it taking more than 10 minutes in extreme cases.
>
> In embedded systems this can be a big issue.
>
> I'm thinking of adding a configuration option to keep the radio on during start.
>
> Whats the general thought about this?

my opinion would be to keep it like that.
it can generate several headaches for several use cases, and break
existing code.

Yes I agree that the startup sequence will change, which is risky, but
it would be an option for people knowing what they are doing.
 
for example when the SIM could change as compared with the previous
boot.

When using this option you should know what you are doing. As I said you
might need to write settings to non-volatile memory since runtime changes
might not apply. And a SIM wont just change in environments where this
option should be used.
 
Then it becomes much harder to recover from this situation.
it would be better to be able to boot the modem in airplane mode,
directly, so that there is no flip-flop effect.

That could be an option, but that will cost up to several seconds of time.
In the systems I'm talking about the boot loader might kick the modem
running to get it registered as quickly as possible.
 

In any case I have never observed 10 minutes.

This is not the regular case. But I have observed this.
 
If this really happens, either the signal is so low that in any case
the link will be pretty unstable, or the stack needs debugging.

I contacted the FAE's from the vendor regarding this. I guess they
want to keep the work load down, but their major complaint was
the way ofono turns off the radio. And even if they would fix their
bugs there will be modems in the field that behaves like this.
But regardless; 10min is a super long time, even if its just
seconds to save, that could be of importance...


I'm not sure its a good idea to introduce this. I need to,
but I wanted to check if there was an interest in the general public.

--Richard