[Gta04-owner] Modem off

Dr. H. Nikolaus Schaller hns at goldelico.com
Mon Sep 16 07:54:46 CEST 2013


Am 16.09.2013 um 04:01 schrieb NeilBrown:

> 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?

Per BGA ball. I just verified and it is even 4mA or 8mA depending on which gpio/mcbsp line we are looking.
The DM3730.pdf data sheet calls it "Buffer Strength".

For both, McBSP4 and HSUSB2, it is 4mA. I.e. a GPIO set to output a high level and driving an unpowered peripheral may draw up to 4mA leakage current.

BR,
Nikolaus



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