[Letux-kernel] letux-4.7-rc7: charging & ethernet gadget

H. Nikolaus Schaller hns at goldelico.com
Wed Jul 20 21:36:08 CEST 2016


> Am 20.07.2016 um 20:46 schrieb Andreas Kemnade <andreas at kemnade.info>:
> 
> Hi,
> 
> On Wed, 20 Jul 2016 10:59:55 +0200
> "H. Nikolaus Schaller" <hns at goldelico.com> wrote:
> 
>> Hi,
>> 
>>> Am 19.07.2016 um 23:37 schrieb Andreas Kemnade
>>> <andreas at kemnade.info>:
>>> 
>>> On Tue, 19 Jul 2016 22:50:44 +0200
>>> "H. Nikolaus Schaller" <hns at goldelico.com> wrote:
>>> 
>>>>> I think I have to study the twl4030 data sheet if there is a
>>>>> common factor.
>>>> 
>>>> First interesting finding:
>>>> 
>>>> Nobody does and can call twl4030_madc_set_current_generator() for
>>>> channel=1, i.e. the BATTEMP channel / ADCIN1.
>>>> 
>>>> Therefore, ITHEN is not touched by the kernel and either U-Boot
>>>> must take care of. Or (I hope) automatic charging enabled by
>>>> hardware does set this bit. Anyways this means ITHEN is off if we
>>>> boot w/o external power.
>>>> 
>>>> The same is true for the current source strength (ITHSENS). So we
>>>> are lucky that 10kOhm at 10µA translates into 100mV. Unless our
>>>> U-Boot modifies these values.
>>>> 
>>>> I remember that I stumbled over a similar thing when developing the
>>>> gpadc driver for the Palmas (twl6037). There we have made it a
>>>> config through DT:
>>>> http://lxr.free-electrons.com/source/Documentation/devicetree/bindings/iio/adc/palmas-gpadc.txt#L26
>>>> 
>>>> This could explain why we sometimes read 56°C. I think this always
>>>> happens if the ITHEN bit becomes reset (why?) and therefore the
>>>> current source is off. Pretending a missing battery. This of course
>>>> will disable automatic charging.
>>>> 
>>>> But it does not explain why we sometimes get more or less random
>>>> values.
>>>> 
>>>> Hm. Wait. Who is powering the current source for ITHEN? What if
>>>> that LDO is broken? Something to keep in mind for another test.
>>>> Although I could not find any reference where the current source
>>>> is powered from.
>>>> 
>>> Well, ITHEN is normally enabled during automatic charge.
>>> If I enable it manually
>>> i2cset -f 0 0x4a 0x97 0x1f 
>>> (BCICTL1)
>>> Temperature shows sane values, so no additional regulator needed for
>>> that. But there are regulators needed for automatic charging...
>> 
>> I have booted with USB cable connected. Which means automatic charging
>> should have been enabled by hardware and U-Boot...
>> 
> if there is a charge on command in boot.scr...

Well, we have a BCIAUTO resistor connected and that should also
enable automatic charging even before power-on. But stuck in the
100mA limitation. Anyways it should at least trickle charge.

> Now I made a quite interesting observation:
> My never-touch 3.7 kernel does not do automatic charging anymore.
> So what do I have
>       a bad dream
> or/and a bad device
> or/and a bad kernel

> 
> or a combination thereof?!
> ?????

hardware virus... Spread through git...

I had indeed similar experiences when it suddently stopped to charge.
Only with 4.3 kernel it simply works:

http://download.goldelico.com/letux-kernel/4.3/

What could be is that a modern kernel programs something into some
eeprom / nvram on the tps65950 chip which makes it fail afterwards.
Until the backup supercap is empty.

Can you wait until the backup battery is discharged? And check if it starts
to work again?

> 
> Very puzzeled regards
> Andreas

BR,
Nikolaus




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