Re: Implement devicetree support for AB8500 Btemp

From: Rajanikanth HV
Date: Wed Sep 12 2012 - 10:33:41 EST

On Tuesday 11 September 2012 04:52 PM, Arnd Bergmann wrote:
> On Tuesday 11 September 2012, Rajanikanth HV wrote:
>>>> +Supplied-to:
>>>> + This shall be power supply class dependency where in the
>> runtime battery
>>>> + properties will be shared across fuel guage and charging
>> algorithm driver.
>>> I probably don't understand enough of this, but shouldn't the other
>> devices
>>> that are supplied by this have a reference to this node rather than doing
>>> it this way around? Why use strings here instead of phandles?
>> This is a logical binding w.r.t power supply event change
>> across energy-management-module drivers where in runtime battery
>> properties are shared along with uevent notification.
>> ref: di->btemp_psy.external_power_
>> changed =
>> ab8500_btemp_external_power_changed;
>> ref: ab8500_btemp.c
>> Need for this property:
>> btemp, fg and charger updates power-supply properties
>> based on the events listed above.
>> Event handler invokes power supply change notifier
>> which in-turn invokes registered power supply class call-back
>> based on the 'supplied_to' string.
>> ref:
>> power_supply_changed_work(..) ./drivers/power/power_supply_core.c
>> In this case how to approach through phandle?
>> ============================
> Sorry, I really tried, but I cannot make sense of what you wrote
> there. Can you try again and describe in full English sentences
> how the hardware blocks are connected
Consider: USB charging:
| |
--(Vbus)-->| USB Charger with |
| Charger FSM (h/w) |
| |
| |(Vbat and other signals)
| __|_____
to | | |(GaugeSense
Charger FSM| | LION | Signal) _____________
| |Battery |----------->|FuelGauge blk|
| |________| |{Coulomb Ctr}|
| | -------------
| <Thermistor>
| |
| | (BatCtrl Signal)
|_______|---------->[Btemp blk]
| |
[ADC] |__Btemp_Low

Note: Charging algorithm is a logical entity.

and what their purpose is?
a) Coulomb counter comprises '12bit adc' and an 'N sample
average/accumulation' logic helps to measure battery capacity
Note: The charge and the discharge current of the battery is
converted to voltage by an external resistor connected
between GaugeSenseP and GaugeSenseN pins.

b) Battery temperature monitoring comprises a comparator which is
enabled only by HW (charger state machine) helps to measure
the thermal threshold
Note: The accuracy of the battery temperature measurement depends
of the accuracy of the thermistor used.

c) Charger provides 'Constant Current Constant Voltage' USB and
Main(Wall) Charging support, it embeds: voltage detection,
thermal protection, Constant voltage charging with programmable level,
clock dithering and battery voltage monitoring

e.g. Correlation between charger and Btemp
- if the battery temperature is higher than âMaxTemp ÂC,
the charger does not start, but is enabled

- if the battery temperature is between 0ÂC and âMaxTempâ ÂC
charging is done in AB8500 Hardware control mode

- charging is done in DB8500 Software control mode, if the battery:
has a voltage higher than the âBattOK Threshold

- If the battery temperature is between -10ÂC and 0ÂC:
charging is done in AB8500 Hardware control mode

- If the battery temperature is below -10ÂC, charging is
done in AB8500 Hardware control mode
> Arnd
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