[Gta04-owner] GTA04 power management.

[Christoph Mair]

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?

Christoph