Re: [MM] Power down during init (was: Re: [MM master] Re: [MM06] [PATCH] sierra: use +CFUN=4 for powering down)

[Dan Williams <dcbw redhat com>]

On Tue, 2012-09-18 at 19:45 +0200, Marius Kotsbak wrote:
> 2012/9/18 Aleksander Morgado <aleksander lanedo com>
>         Hey Dan and Marius,
>         
>         >
>         >> Power Up = enabled
>         >> Power Down = disabled
>         >>
>         >> So we already have those states in ModemManager via the
>         Enable() method
>         >> and the modem states.  It's just that not all devices
>         actually implement
>         >> the low-power mode when disabling, partially because we're
>         not always
>         >> sure of the side-effects.
>         >>
>         >
>         > The problem here isn't that we don't have a safe power-down
>         command; the
>         > problem is that even if we have it, we don't use it just
>         after plugging
>         > in the modem:
>         >   initialized -> locked -> disabled
>         >
>         > But for that 'disabled' state we didn't run the power-down
>         command even
>         > if we have it, so the radio interface may be powered on
>         there. That's
>         > the thing to fix by running the disabling sequence just
>         after
>         > initialization. If there is no default power down command,
>         then we would
>         > run the disabling sequence but without any power down
>         command, so no big
>         > deal.
>         >
>         
>         The attached patch runs just a new power-down step during the
>         modem
>         initialization, to ensure it starts in low power mode. Adding
>         a new step
>         to run power-down instead of running the whole disabling
>         sequence seemed
>         a better option, as the disabling sequence really assumes we
>         were
>         previously enabled. Note that this patch just re-uses the
>         power-down
>         implementation given in each plugin, which we previously used
>         only
>         during the disabling sequence.
>         
>         Given that it's quite a big change, can you guys try it with
>         some of the
>         modems that we know have given issues before with these
>         things? Thinking
>         on Sierra modems specifically here. I've got a Wavecom modem
>         which also
>         had issues with CFUN (e.g. rebooting on CFUN=1 if it was
>         already in
>         CFUN=1), but won't be able to test it until Friday.
> 
> Tested my ZTE MF820D and seems to work nice. Would this be possible to
> backport to MM_06?

It could be, patches accepted unless we get to it first :)

> Btw, is this expected?:
> 
> model: '+CGMM: "MF820D"'

A bug, the handler code here probably needs to strip out the CGMM if
found.  Most devices don't actually prefix the CGMM response with
"+CGMM" so the code wasn't built to handle that, either in 05/06 or git
master I guess.

Dan