[Gta04-owner] Donations to investigate suspend current?

NeilBrown neilb at suse.de
Thu Apr 10 09:06:40 CEST 2014


On Thu, 10 Apr 2014 08:26:34 +0200 Christoph Mair <christoph.mair at gmail.com>
wrote:

> Am 10.04.2014 01:49 schrieb "Benjamin Deering" <ben_deering at swissmail.org>:
> > Would it make sense to collect donations specifically to fund some
> thermal imaging to see what has changed?
> 
> Measuring less than 20mA with thermal imaging is quite hard, especially if
> you've got a multilayer board with lots of copper in it which spreads the
> heat...
> 
> I have the possibility to get my hands on a FLIR camera (no funds needed
> for this) but I will need some assistance when taking pictures. Since I
> didn't have the time to play with my gta04 recently I don't know how to
> switch on/off all of the peripherals on recent kernels.
> 
> Another approach would be to buy a semi broken board from GDC (if some are
> still available), remove component after component and measure the suspend
> current after each step.

I seriously think this would achieve nothing - it is much too big a hammer.

I could easily be wrong, but I think that a lot of the remaining power drain
is related to the USB interface to the Option 3G chip.
I'm certain that the drive for the EHCI interface on the OMAP3 has power
management issues.  I suspect there might be interactions between it and the
usb transceiver (parallel to serial converter) which waste power too.

Unfortunately the only way I can think of to make progress is to pour over
the code in detail, read as much documentation for the EHCI interface as I
can find, and try some things out.  i.e. lots and lots of work with no
certainty of reward.

NeilBrown
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