Re: [MM master] Re: [MM06] [PATCH] sierra: use +CFUN=4 for powering down

[Dan Williams <dcbw redhat com>]

On Mon, 2012-09-10 at 14:21 +0200, Aleksander Morgado wrote:
> >>>>>>>> See patch attached.
> >>>>>>>>
> >>>>>>>> sierra: use +CFUN=4 for powering down
> >>>>>>>>
> >>>>>>>>     plugins/mm-modem-sierra-gsm.c |   32
> >>>>>>>> ++++++++++++++++++++++++++++++++
> >>>>>>>>     1 file changed, 32 insertions(+)
> >>>>>>> This also needs to be intregrated in the master branch version.
> >>>>>>> Attached
> >>>>>>> is my attempt to do it, but it seems not to work. I see no effect of
> >>>>>>> disabling the modem with "mmcli -m X -d".
> >>>>>> See review below.
> >>>>>>
> >>>>>>> Also, it seems like the power down is not done before the modem
> >>>>>>> enters
> >>>>>>> disabled state at startup of MM or after modem is inserted, so I
> >>>>>>> filed a
> >>>>>>> bug about that:
> >>>>>>>
> >>>>>>> https://bugzilla.gnome.org/show_bug.cgi?id=683681
> >>>>>>>
> >>>>>> Yes, that's a known issue, see TODO in the source tree.
> >>> The text there is slightly incorrect. It does not help if the modem is
> >>> in low power mode when started (some might also be configured to be),
> >>> because at least in the Sierra plugin, it is waked up to CFUN=1 in the
> >>> init anyway. This could be avoided by accepting CFUN mode 4 and 7 as
> >>> well. But then it must be changed to mode 1 when connecting.
> >>>
> >>> I am not sure if all the init steps are possible in low power mode.
> >>>
> >> CFUN=1 is sent when *enabling* the modem, not during init. All the init
> >> steps should really be possible while in CFUN=4 low power mode as that
> >> should only kill the radio power.
> > 
> > Sorry, I did not test it or dig deep enough in the code. If I sent the
> > modem to CFUN=4, it actually keeps this state after the init, and
> > enabling works fine.
> > 
> >>
> >> Also, for Sierra modems there's the problem that CFUN=1 may actually
> >> reboot the modem, so the problem with powering down the radio with
> >> CFUN=4 in Sierra is that this may require a reboot/reprobing of the
> >> modem afterwards :-/ IIRC Wavecom (which also suffers from the same
> >> issue) had a CFUN=1,0 to try to go into full functionality mode without
> >> rebooting, not sure if Sierra has something similar.
> > 
> > Seems my Sierra modem has the same:
> > 
> > +CFUN: (0-1,4-7),(0-1)
> > 
> > but the default is ",0" on my modem, as "CFUN=1,1" behaves just like
> > "CFUN=1", but "CFUN=1,1" causes a restart.
> > 
> > We could do a detection of the right version by using some regex of the
> > CFUN=? output.
> > 
> 
> Or, just try first with AT+CFUN=1,0 and if we get any error, retry with
> the original AT+CFUN=1. This can easily be done with an AT sequence.
> Note that anyway the power-up command needs to be sent *only* if not
> already in the full-functionality mode (that's why the Sierra and
> Wavecom plugins have already the AT+CFUN? check).

Sierra 2.8 AT docs (which aren't very up-to-date) suggest that AT
+CFUN=x,x is supported by most modems, but only lists states 0 and 1.
So we'd probably need to parse AT+CFUN=? and then figure out if we *can*
do state 4 or not.  But we could also just retry like you suggest.

Dan