[Gta04-owner] GTA04 power management.

[NeilBrown]

On Mon, 26 Dec 2011 01:46:56 +0100 Christoph Mair <christoph.mair at gmail.com>
wrote:

> On Sat, Dec 24, 2011 at 6:10 AM, NeilBrown <neilb at suse.de> wrote:
> >  I'm particularly looking at suspend-mode.  While runtime power management
> >  (turning the CPU on/off dynamically as needed and adjusting voltage) is
> >  attractive it can never save more power than full suspend, so suspend mode
> >  will show us the minimum power usage without turning the device off
> >  completely.
> >
> >  I'm current measuring about 8%/hour battery discharge while in suspend mode
> >  which corresponds to approximately 100mA current drain.  When the device is
> >  off I lose about  1%/hour which is around 10mA (the precision of these
> >  measurements isn't great so there is a lot of rounding here) which is
> >  presumably attributed to the OPTION GSM module (and matches what HNS said it
> >  would be).
> >
> >  So that suggests around 90mA still being used by something else.
> >
> >  I've turned off the power supplies for WIFI, BT, GPS antenna, sensors.
> >  I've turned off VDD1 and VDD2 to the CPU, and the various power supplies for
> >  USB and the battery charger (VINTANA, VINTDIG).  All the leds are off.
> >
> >  All that should be left on are VDDIO aka 1V8, and REGEN aka 3v3.  It seems
> >  that these need to be on by design.
> >
> >  With the GPS off (it is, I checked) and the LEDs off and none of the
> >  other peripherals enabled, 3V3 shouldn't be providing much current as
> >  discussed previously.  The only things of any significance I can see driven
> >  1V8 are:
> >
> >  - The 26MHz clock.  This seems to be on all the time where I (naively)
> >    would have expected it to be enabled by the CLKEN output from the TWL4030.
> >    I assume there is a reason for that?  How much current does it use?
> >
> >  - Some power to the CPU.  If I read it correctly it is only supplying
> >    - DDS - the display subsystem
> >    - POP-DDR and POP_FLASH - the Package on Package memory.
> >
> >    I would expect the DDS to be off (not sure how to check yet) and the
> >    memory to be in self-refresh mode.
> >
> >  Any guesses were that 90mA is going?  I would understand a 10mA draw, but
> >  90mA seems a bit steep for a sleeping device.
> Could it be possible that the PWM output is still high and the
> backlight boost converter is not switched off?

Thanks for the suggestion.
I've checked and the PWM is definitely being turned off:

void pwm_disable(struct pwm_device *pwm)
{
	printk("PWM_DISABLE\n");
	omap_dm_timer_enable(pwm->dm_timer);
	omap_dm_timer_stop(pwm->dm_timer);
	omap_dm_timer_disable(pwm->dm_timer);
}

pwm_disable is definitely called before suspend.

So I don't think it can be that.

NeilBrown
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