andy git 06/15 suspend/resume observations

[Andy Green]

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Somebody in the thread at some point said:

| Yes, I only get the pop now on resume.

OK Great looks like we are working on the right issue.

|> BTW Mark... we use the sideband path for voice data... no *ALSA* device
|> is opened during that time, but we could do with 50K source impedence to
|> Vref not 500K which happens shortly after you close an alsa device.  How
|> do you think we should come at that?  Keep 50K up while there is any
|> active analogue routing path open?  Or a new ALSA switch, or something
|> else?
|
| In my application, I always have an *ALSA* device open when in a call. I
| open different pseudo devices depending on the mode (normal with
| speaker, normal in a call, speaker out in a call, headphone stuff, etc).

Yes I don't think it makes any trouble here, it's just that solid Vref
is still needed even if you are only using, say, a Mic input on an
analogue path and not involving the CPU or Alsa at all.  It seemed like
the driver currently believes it only has to maintain lower stability
Vref if the CPU / PCM interface is not up, but that isn't true in the
default rootfs case anyway.

| I'll try to see if I can get it to happen with headphone jack. I can
| also try disabling the radio interface to see if it will hang without a
| GSM wakeup. Also keep in mind there is a long period of being in suspend
| before an attempted resume. Make sure you give it 10 minutes or more
| between suspend/resume.

Wah I never really give it 10 minutes :-(  OK.  But this is going to be
frustration hell.

I also wonder what it is that counts out the 10 minutes to "know if it
should go wrong".  Network timeouts from NFS external host?  The GSM
chips are awake and can tell they didn't get talked to for 10 minutes?
Waits for BATFULL somehow?  We turned a voltage rail off we shouldn't have?

I guess with NFS rootfs you always have USB in during suspend, it might
be interesting to see if the problem ever comes with local rootfs and no
USB in during suspend.  If you want some tips on SD Card boot you're
welcome.

- -Andy
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