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

[Marius Kotsbak <marius kotsbak gmail com>]

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?

Btw, is this expected?:

model: '+CGMM: "MF820D"'

--
Marius