Hi,

On 06/01/2017 04:39, Chen-Yu Tsai wrote:

 Hi,

On Tue, Jan 3, 2017 at 12:37 AM, Quentin Schulz
[off-list ref] wrote:

[...]

quoted

+       case POWER_SUPPLY_PROP_CURRENT_MAX:
+               ret = regmap_read(axp20x_batt->regmap, AXP20X_CHRG_CTRL1, &reg);
+               if (ret)
+                       return ret;
+
+               reg &= AXP20X_CHRG_CTRL1_TGT_CURR;
+               val->intval = reg * 100000 + 300000;
+               break;

This controls the charge current. I believe the correct property to use
is CONSTANT_CHARGE_CURRENT. And you should add CONSTANT_CHARGE_CURRENT_MAX
which returns the highest possible setting.

ACK.

Also letting the user control this might not always be a good idea.
IIUC, LiPo batteries can only be charged at 1C, where C is the
rated capacity (X mAh).

OK. Should I get the charge current from a DT property then?

Like "x-powers,charge-current = <300000>;"
It's close to what has been done in bq24257_charger for example.

[...]

quoted

+static enum power_supply_property axp20x_battery_props[] = {
+       POWER_SUPPLY_PROP_PRESENT,
+       POWER_SUPPLY_PROP_ONLINE,
+       POWER_SUPPLY_PROP_STATUS,
+       POWER_SUPPLY_PROP_VOLTAGE_NOW,
+       POWER_SUPPLY_PROP_CURRENT_NOW,
+       POWER_SUPPLY_PROP_CURRENT_MAX,
+       POWER_SUPPLY_PROP_HEALTH,
+       POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN,
+       POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN,
+       POWER_SUPPLY_PROP_CAPACITY,

You can also add POWER_SUPPLY_PROP_TECHNOLOGY, which would return
POWER_SUPPLY_TECHNOLOGY_LIPO.

Hum.. There are also POWER_SUPPLY_TECHNOLOGY_LION,
POWER_SUPPLY_TECHNOLOGY_LiFe and POWER_SUPPLY_TECHNOLOGY_LiMn which are
all Lithium-based batteries. From the datasheet, it can take a "single
cell Li-battery (Li-Ion/Polymer)". So I guess it's either
POWER_SUPPLY_TECHNOLOGY_LION or POWER_SUPPLY_TECHNOLOGY_LIPO.

It is also possible to do POWER_SUPPLY_PROP_CHARGE_TYPE. According
to the manual, if the battery is charging, it is in constant current
mode (POWER_SUPPLY_CHARGE_TYPE_FAST) when V_battery < V_target.
When V_battery == V_target, it is in constant voltage mode, though
I don't think this is the same as POWER_SUPPLY_CHARGE_TYPE_TRICKLE.
When it is not charging, you can return POWER_SUPPLY_CHARGE_TYPE_NONE.

ACK, I'll look into that.

Thanks,
Quentin

-- 
Quentin Schulz, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com