USB current limit when phone off
andy at openmoko.com
Thu Feb 5 15:12:44 CET 2009
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Somebody in the thread at some point said:
| On Thu, Feb 5, 2009 at 14:42, Andy Green <andy at openmoko.com> wrote:
|> You can confirm what the phone thinks about the charging context with
|> cat /sys/class/i2c-adapter/i2c-0/0-0073/pcf50633-mbc/usb_curlim
|> Unless we rewrite it when we're shutting down it should stick while
| Yes, I am almost sure usb_curlim was 100mA (I have a little android
| app to read this value. I will test again to be sure..).
| And it did pull this from charger from what I could see (charger led
| and battery charge variation)
| But when shutdown it seems it did pull more current.
| (then as soon as I powered on the phone again -> back to 100mA)
Yes Qi forces it to 100mA limit very quickly after the CPU starts up, so
it's hard to separate the act of starting up from the definite forcing
of this to 100mA.
| I just tried with an old QTextended partition -same Qi, but old
| kernel-) and there on shutdown it stopped alimentation completely
| (charger led turns from amber to green).
Right, Qi doesn't touch much on the PMU and what it does touch the
pcf50633 kernel driver mostly overwrites, I didn't expect we find Qi is
It can be kernel or I suppose the rootfs but it'd be strange.
| So normally, quitting Android it should have stick to 100mA max ?
| And what about battery max current charge (the setting that was
| recently made writable) ? Should it persist on shutdown too?
Yes, the settable charge current that Balaji added sticks in "off" under
the same rules as the charging enable action, it's only lost in PMU
NOPOWER when there's no charger power, no battery power and even no
backup battery power.
So during all these tests we never hook to anything but a "dumb"
charger? The kernel never gets the idea during that session that it
could pull 500mA legitimately and somehow wrongly hold on to that idea?
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