My Gta02s wont charge / chgena = 0 by default
joerg at openmoko.org
Mon Jun 23 19:04:18 CEST 2008
Am Mo 23. Juni 2008 schrieb Andy Green:
> Somebody in the thread at some point said:
> | Andy Green wrote:
> |> So we should probably also want to come up from pcf50633-standby
> |> with charging disabled there until we can set correct parameters.
> | This brings us back to the problem what we do if we have an dead
> | battery. (That is, < 2.5V.)
> | If the charger is off, there doesn't seem to be an alternative
> | path to deliver power to Vsys. Thus, the PMU never lets us enter
> | Active (for Vsys is too low), and it will also not charge the
> | battery (since the charger is disabled).
> | I think we have to look for a solution along the lines of setting
> | chgena = 1 and live with that 500mA spike until the CPU gains
> | control.
> There is probably some delay between power coming and charging starting
> anyway. And it should be some hundred and so ms until the CPU comes up.
> ~ And we don't have much choice AFAIK.
> Charger disabled is no problem if it's true the CPU is going to come up,
> it will come up and enable the charger. We need to confirm we can
> always get the CPU to come up on power insertion, then we are OK I
> think... is the "shutdown -h now" case OK, where he remains powered from
> laptop USB that is not validly enumerated after he shuts down but maybe
> he sits there off eating 500mA?
> It's pretty strange that "disable charger" --> "don't even power the
> device from USB"... does it explicitly say that anywhere or is that just
> what we are empirically seeing? I saw that these paths are considered
> part of the charger unit but not really that charging and device
> function are bound together so tightly.
Well I didn't check yet (had a busy day on some other issue ;-), but I think
if there's some little chance we might fail on bringing up the CPU, we have
to avoid to ever enter this state. Means I'd prefer to have charger enabled
all the time, even if this means we are violating specs of USB for some short
time due to the stupid reset of I-usb-max to 500mA.
Saturday Jan mentioned there allegedly is some exception for USB allowing a
spike up to 500mA for some ms, for init purposes. And Werner made me notice
the function in u-boot. So maybe we are even fine with the chgena=1
and "spike" scenario Werner mentioned. And I wouldn't care too much about
breaking any specs here, other devices (hd-drives) are much worse and host
controllers usually know to cope with this, at least they won't go up in
*sigh*, I _love_ barrel connectors ;-) Just to wires and some 5V, chargers
available all over the world on some shop that's never more than 100m away,
for really few money. And receptacle could live happily besides the mini-usb.
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