[Gta04-owner] Modem off

NeilBrown neilb at suse.de
Mon Sep 16 04:01:08 CEST 2013


On Sun, 15 Sep 2013 10:29:48 +0200 "Dr. H. Nikolaus Schaller"
<hns at goldelico.com> wrote:

> So I can only come to the same conclusion that the EHCI within the OMAP is not aware of a "disappeared" USB3322 and therefore does not suspend properly.

I think this is likely.
I seems to connect with the errata you mentioned earlier:
  http://www.ti.com/lit/er/sprz319e/sprz319e.pdf

As I understand it, when the OMAP EHCI goes to sleep it tells the PHY to go
to sleep.  The USB3322 PHY is slow in responding so that the OMAP EHCI thinks
the phy has woken up again, so it wakes up.
This leaves the EHCI awake, and possibly not communicating properly with the
PHY, resulting in excess power consumption and occasional communication
hiccups.

I think to "solve" this we would need to explicitly power down the EHCI and
reset the PHY.  It is fortunate that incoming-call alerts come through a
separate GPIO, so we can power down the USB without missing calls etc.
Hopefully.

> 
> And, I have to revise my statement about leakage currents. If the McBSP4 and the TWL-PCM drivers are not disabled but fully powered during suspend (i.e. not just driven high by weak pullups) they can provide 2mA (or even more) leakage current into the inputs of the powered down modem.

Is that 2mA per line, or 2mA total?

This is something I will try to look into over the next few days.

Thanks for your analysis.

NeilBrown
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