[SHR-Unstable] Forcing fast-charge

Joerg Reisenweber joerg at openmoko.org
Thu May 7 13:30:41 CEST 2009

Am Do  7. Mai 2009 schrieb Cédric Berger:
> 2009/5/7 Joerg Reisenweber <joerg at openmoko.org>
> >
> > Correct - usbdevstat allows 100mA, 500mA, 1A, and suspend (Tbl. 98, 
> > anyway...
> > Setting chg_curlim won't help whatsoever, as you can set it only during
> > device
> > powered up and system running, and during this time the system consumption
> > USB-to-SYS will add to the chg_curlim you set. So you exceed intended USB
> > current by setting chg_curlim to the value you intend for USB current, 
> > to shutdown device after that and hope to reach 'correct' USB current then
> > eventually - that's silly.
> >
> >
> In my case I used setting chg_curlim also for when phone is on.
> Yes chg_curlim does not help to force usb real current to ie. 750m exactly.
> But ! This way I could have my phone use approx 750mA when on (by setting
> chg_curlim to 500mA).
> Of course it may sometimes consume up to 1A if needed (the peaks I was
> talking about...).
> But this is ok in my case for my weak dumb charger.
> What would not be ok is having chg_curlim not forced and phone pulling 1A
> for 30 minutes continuously while charging the battery faster than I need...
> (And usb_curlim to 500mA would on the other hand not charge quickly enough
> (about 300mA).)

So you think the STANDARD kernel should care about this rather exotic case 
which isn't specified properly (how long would this charger see the "1A 
sometimes"?) and needs massive care from userland anyway? I mean, there's 
some reason PCF50633 is built this way, huh? We got enough problems caring 
about real hw-glitches in this chip. I don't think it's recommendable to 
tweak it even further far beyond what's normal usecase.

btw your concept isn't working as you said yourself the USB current is reset 
to 500mA on powerdown. So how could you charge with 750mA? If system is 
powered up odds are it will take away 250mA. On powerdown state it seems to 
me there's no way at all to charge with 750mA. I really don't see the 
rationale behind all this.

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