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

[Ben Chan <benchan chromium org>]

I briefly tested the patch on Samsung/Icera Y3300/Y3400 modems.
Planning to do some more stress tests later this week.

It may not be a bad idea to allow a plugin to override the
power-down-on-initialization behavior.

Thanks,
Ben

On Tue, Sep 18, 2012 at 7:24 AM, Aleksander Morgado
<aleksander lanedo com> wrote:
> 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.
>
> Cheers!
>
> --
> Aleksander
>
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