[Gta04-owner] 3.2-rc6-gta04 - another week, another rc.

NeilBrown neilb at suse.de
Tue Dec 20 02:21:18 CET 2011

On Mon, 19 Dec 2011 22:32:15 +0100 "Dr. H. Nikolaus Schaller"
<hns at goldelico.com> wrote:

> Am 19.12.2011 um 21:21 schrieb NeilBrown:
> > On Mon, 19 Dec 2011 13:06:13 +0100 "Dr. H. Nikolaus Schaller"
> > <hns at goldelico.com> wrote:
> > 
> >> Hi Neil,
> >> 
> >> Am 19.12.2011 um 12:53 schrieb NeilBrown:
> >> 
> >>> On Mon, 19 Dec 2011 11:03:40 +0100 "Dr. H. Nikolaus Schaller"
> >>> <hns at goldelico.com> wrote:
> >>> 
> >>>>> 
> >>>>> I'll have to build myself a uboot ... are there any tricks I need to know, or
> >>>> 
> >>>> What do you intend to change?
> >>> 
> >>> Possibly nothing - just want to use the latest and want to know that I can
> >>> build it myself.
> >> 
> >> If you have ideas or find issues, please report here:
> >> 
> >> http://projects.goldelico.com/p/gta04-uboot/issues/
> >> 
> >> U-Boot-bugs are usually easier and faster fixed than in the kernel.
> >> 
> >>> I have an idea that it might be good to drop 3V3 for a few milliseconds early
> >>> in boot to make sure that the GPS is off so that when we toggle the
> >>> on/off line we can be certain what state it is in.  That would best be done
> >>> in uboot I think.
> >> 
> >> I am not sure if that is possible at all. The 3V3 line is coming from
> >> a LDO that is a slave of the REGEN signal of the TPS65950. I.e.
> >> it becomes enabled by hardware. And it can't be turned off because
> >> there are other chips (e.g. the USB3322) which is not allowed to receive
> >> 1.8V signals on the inputs if there is no 3V3.
> > 
> > Oh - that's a shame.
> > 
> > Is it safe to turn 3V3 off during suspend or is it meant to stay on the
> > whole time?
> It will stay on all the time since it is part of the proper power on/off sequencing
> scheme. There is a timing diagram in the TPS65950 and DM3730 data sheets.
> So suspend has to take care that it switches all devices to low power mode
> (e.g by activating RESET or sending some I2C commands). According to the
> data sheets this is possible. So 3.3V remains active but the system draws some
> 50 uA from the 3V3 rail. And the modem draws 3-10 mA from VBATT.

OK.  So just to make this concrete - my reading of the schematics says that
3V3 is used for :

 P204 - The LCD controller. (TD28TTEC1)
         The LCD can fairly clearly be turned off.
 D-AUX, D-PWR - The LEDS.  The controller itself is on 1V8 and presumably
        cannot be turned off.
        So turning all the leds off will remove any current drain here.
 U702 - The video-out amplifier.  This is controlled by GPIO23 so that is
        easy to manage. 
 U901 - internal USB phy for WWAN.  GPIO174 on reset and stopping the clock
        from the usb port on the processor should stop that using power.
 U1102 - level shifter for wifi chip.  Presumably when no data is flowing
        it doesn't use significant power.
 M1201 - GPS as already discussed
 U1401 - the FM transceiver.  Presumably you can tell it to power down
         the RF bits over the I2B bus?
 U1501 - serial port driver which can be powered-down with GPIO13, though that
         turns the IrDA on which is powered straight from the battery.
         Does that mean one of these has to be on always?  I guess the serial
         driver doesn't use much current?

 U1801 - VGA drivers - currently not implemented.

So yes, most things can be clearly turned "off" - nor sure about serial or FM

> It is also that the 1.8V is not shut down not keep DRAM alive. And to keep
> the GPIO pins active that are looking for wakeup impulses. But one core
> voltage is completely shut down (I think VDD2).
> But I have no real experience with it. We may have to do some tests as soon
> as suspend/wakeup works. We can suspend the CPU and check the power
> consumption and try to find out which chips are not shut down.
> I would e.g. suspect the TSC2007 driver. It could be sent to deep sleep
> where it just monitors the touch screen and can generate a PENIRQ
> wakeup if someone touches the screen. 

I'm not sure I want the screen to be sensitive except when it is fully on.
And I presume you cannot power much of the CPU down while the display is on??

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