Motorola Droid 4 progress, power consumption

* Pavel Machek [off-list ref] [180504 20:22]:

Hi!

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user at devuan:/sys/class/power_supply/battery$ date; cat current_now
current_avg
Thu May  3 09:33:07 CEST 2018
-56000
-72308
user at devuan:/sys/class/power_supply/battery$ date; cat current_now
current_avg
Thu May  3 09:33:08 CEST 2018
-37000
-211362

I recall it just being calculated based on the time between
the reads. Hard to say what it does, -ENODOCS.. Maybe the mc13783
PMIC docs have something similar.

Hmm. current_avg is world readable; if it does changes to the
hardware, that's somehow bad.

No it just calls cpcap_battery_cc_get_avg_current() that calculates
the average from last time it got sampled based on number of samples
collected between the two reads. Seems to match what I see on my
power supply here.

But I guess I can sample charge_counter every minute or so and get
what I need?

Not sure what the max time range is for the PMIC, but yeah I'd
assume once a minute is duoable. Maybe compare it to the chart
you already have?

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Hmm oh and the POWER_SUPPLY_CHARGE_COUNTER value should be monitored
by your libbattery and it's low value and high value should be saved
to a file. Low should be saved when we get the battery low interrupt
and battery state changes to POWER_SUPPLY_CAPACITY_LEVEL_CRITICAL.
High value should be saved on POWER_SUPPLY_CAPACITY_LEVEL_FULL.

Then when you know the high value and low value, you can calculate
the remaining capacity based on the current value and
POWER_SUPPLY_POWER_AVG.

I'll look into that... but probably will do experiments with python,
first.

Sure. The reason why I think we should not do it in the kernel in
addition to the earlier reasoning is that we don't have a place
to store the min and max values across reboot. I think there's
some flash on the battery over 1w bus, but it probably just
contains battery serial number or something and is not intended
for writing much to it. I guess the min and max values should be
really keyd based on this battery id in case the battery gets
changed.

I agree this should not be done in kernel as it requires persistent
storage.

Battery is not user-replacable (and this will recalibrate itself on
charge/discharge cycle) so.. I don't think keying is strictly
neccessary for D4.

Yeah right, that can be added later on if needed if you just
plan accordingly. It's replaceable with a T5 after you peel off the
sticker from the corners :)

Regards,

Tony