[Gta04-owner] various powermanagement issues

Neil Brown neilb at suse.de
Mon Oct 19 01:08:02 CEST 2015


xdrudis at tinet.cat writes:

> On Sun, Oct 18, 2015 at 08:20:13AM +0200, H. Nikolaus Schaller wrote:
>> 
>> 
>> Yes, that is indeed a known problem for a long time. It could be solved by
>> modifying the MLO so that it turns on 500mA charging within the first 1-2 seconds.
>> 
>> Currently, Linux must boot up to a point to enable 500 mA charging. This takes
>> 30-60 seconds.
>> 
>> Now a discharged battery is charged by ~50mA (trickle charge) until the device
>> turns on as soon as the battery voltage reaches 3.3V. At that point it may be
>> charged for just 1%.
>> 
>> If this is not enough for booting to Linux (30-60 seconds @ 400 mA) full
>> charging will fail.
>>
>
> I haven't refreshed my memory, but I assume the reason is linux has a
> complete enough USB stack to negotiate 500mA but MLO has a very more
> basic USB stack (or none).

The reality is much more prosaic (i.e. boring) than that.
People have hacked Linux to make it work reasonably without going too
far out of spec.  Nobody has hacked the MLO in the same say.  That's
really all there is to it.

One of my many frustrations is that the "correct" way to check if a
charger is attached is to send a signal down the D+ line and see if it
comes back along the D- line.  i.e. check if D+ and D- are shorted.
(I think that is a gross oversimplication, but it gives the idea).

I believe that the TWL4030 USB phy is able to perform this test, but I
cannot actually get it to work.
So the only sort of charger we can reliable detect is the Openmoko
charger that puts a resistor between the ID pin an Ground.

It would be quite easy to get MLO to test for that resistor and enable
high-current changing.  I'd really like to more general "USB standard
charger" test.  But I cannot make it work.

(I guess I should hack the MLO, because I mostly charge with the
openmoko charger...)

NeilBrown
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