Can't boot Freerunner without battery - Was: Re: unable to start up freerunner after batterie was full down
openmoko at mazikeen.demon.co.uk
Mon Jul 14 18:12:27 CEST 2008
The phone can't take >100mA from USB without asking, and the PMU enforces
this. The AC PSU can supply more than this, as can most USB ports, but at
this stage of the process the checks to see if this is available can't be
done so we're limited to 100mA. When the old uBoot powered up the assorted
chips the current would spike higher than 100mA which was fine with battery,
but without battery the PMU would cut the power to stop violation of the USB
100mA limit. The new uBoot changes the power up sequence to try to keep the
current below 100mA at all times. That's a rough outline anyway - full
discussion in the kernel list archive.
On Monday 14 July 2008, Steven ** wrote:
> The battery can delivery more power than the AC USB adapter?
> On Mon, Jul 14, 2008 at 1:18 AM, Joerg Reisenweber <joerg at openmoko.org>
> > Am Mo 14. Juli 2008 schrieb Steven **:
> >> Perhaps it's been said before and I missed it... But why can't the
> >> Neo boot off USB power alone?
> > Boils down to sth like powering up a whole town after blackout.
> > All components drawing a spike of energy same moment, which USB can't
> > deliver. ->next blackout.
> > Werner's new U-boot extenuates this somewhat, but as much of this is
> > inside PMU hardcoded, SW can't do much.
> > /jOERG
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