power: supply: rk817: Update battery capacity calibration

The battery capacity calibration function continues to be a source of
bugs for end users, especially when coming out of suspend. This occurs
when the device has incorrect readings for voltage, and causes the
current code to set fully charged capacity incorrectly.

Add checks to ensure we don't attempt a capacity calibration when we
have invalid voltage values or no battery present, and remove the code
that attempts to automatically set the fully charged capacity in lieu of
making the value writeable. This way userspace is able to adjust the
fully charged capacity for a degraded battery.

Signed-off-by: Chris Morgan <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Sebastian Reichel <[e-mail]>

drivers/power/supply/rk817_charger.c

···
 static int rk817_bat_calib_cap(struct rk817_charger *charger)
 {
 	struct rk808 *rk808 = charger->rk808;
-	int tmp, charge_now, charge_now_adc, volt_avg;
+	int charge_now, charge_now_adc;
 	u8 bulk_reg[4];
+
+	/* Don't do anything if there's no battery. */
+	if (!charger->battery_present)
+		return 0;
+
+	/*
+	 * When resuming from suspend, sometimes the voltage value would be
+	 * incorrect. BSP would simply wait two seconds and try reading the
+	 * values again. Do not do any sort of calibration activity when the
+	 * reported value is incorrect. The next scheduled update of battery
+	 * vaules should then return valid data and the driver can continue.
+	 * Use 2.7v as the sanity value because per the datasheet the PMIC
+	 * can in no way support a battery voltage lower than this. BSP only
+	 * checked for values too low, but I'm adding in a check for values
+	 * too high just in case; again the PMIC can in no way support
+	 * voltages above 4.45v, so this seems like a good value.
+	 */
+	if ((charger->volt_avg_uv < 2700000) || (charger->volt_avg_uv > 4450000)) {
+		dev_dbg(charger->dev,
+			"Battery voltage of %d is invalid, ignoring.\n",
+			charger->volt_avg_uv);
+		return -EINVAL;
+	}
 
 	/* Calibrate the soc and fcc on a fully charged battery */
 
···
 					  bulk_reg, 4);
 		}
 	}
-
-	/*
-	 * Calibrate the fully charged capacity when we previously had a full
-	 * battery (soc_cal = 1) and are now empty (at or below minimum design
-	 * voltage). If our columb counter is still positive, subtract that
-	 * from our fcc value to get a calibrated fcc, and if our columb
-	 * counter is negative add that to our fcc (but not to exceed our
-	 * design capacity).
-	 */
-	regmap_bulk_read(charger->rk808->regmap, RK817_GAS_GAUGE_BAT_VOL_H,
-			 bulk_reg, 2);
-	tmp = get_unaligned_be16(bulk_reg);
-	volt_avg = (charger->voltage_k * tmp) + 1000 * charger->voltage_b;
-	if (volt_avg <= charger->bat_voltage_min_design_uv &&
-	    charger->soc_cal) {
-		regmap_bulk_read(rk808->regmap, RK817_GAS_GAUGE_Q_PRES_H3,
-				 bulk_reg, 4);
-		charge_now_adc = get_unaligned_be32(bulk_reg);
-		charge_now = ADC_TO_CHARGE_UAH(charge_now_adc,
-					       charger->res_div);
-		/*
-		 * Note, if charge_now is negative this will add it (what we
-		 * want) and if it's positive this will subtract (also what
-		 * we want).
-		 */
-		charger->fcc_mah = charger->fcc_mah - (charge_now / 1000);
-
-		dev_dbg(charger->dev,
-			"Recalibrating full charge capacity to %d uah\n",
-			charger->fcc_mah * 1000);
-	}
-
-	/*
-	 * Set the SOC to 0 if we are below the minimum system voltage.
-	 */
-	if (volt_avg <= charger->bat_voltage_min_design_uv) {
-		charger->soc = 0;
-		charge_now_adc = CHARGE_TO_ADC(0, charger->res_div);
-		put_unaligned_be32(charge_now_adc, bulk_reg);
-		regmap_bulk_write(rk808->regmap,
-				  RK817_GAS_GAUGE_Q_INIT_H3, bulk_reg, 4);
-		dev_warn(charger->dev,
-			 "Battery voltage %d below minimum voltage %d\n",
-			 volt_avg, charger->bat_voltage_min_design_uv);
-		}
 
 	rk817_record_battery_nvram_values(charger);
 
···
 	return IRQ_HANDLED;
 }
 
+static int rk817_bat_set_prop(struct power_supply *ps,
+			      enum power_supply_property prop,
+			      const union power_supply_propval *val)
+{
+	struct rk817_charger *charger = power_supply_get_drvdata(ps);
+
+	switch (prop) {
+	case POWER_SUPPLY_PROP_CHARGE_FULL:
+		if ((val->intval < 500000) ||
+			(val->intval > charger->bat_charge_full_design_uah))
+			return -EINVAL;
+		charger->fcc_mah = val->intval / 1000;
+		return rk817_bat_calib_cap(charger);
+	default:
+		return -EINVAL;
+	}
+}
+
 static enum power_supply_property rk817_bat_props[] = {
 	POWER_SUPPLY_PROP_PRESENT,
 	POWER_SUPPLY_PROP_STATUS,
···
 	POWER_SUPPLY_PROP_VOLTAGE_AVG,
 };
 
+static int rk817_bat_prop_writeable(struct power_supply *psy,
+				    enum power_supply_property psp)
+{
+	switch (psp) {
+	case POWER_SUPPLY_PROP_CHARGE_FULL:
+		return 1;
+	default:
+		return 0;
+	}
+}
+
 static const struct power_supply_desc rk817_bat_desc = {
 	.name = "rk817-battery",
 	.type = POWER_SUPPLY_TYPE_BATTERY,
 	.properties = rk817_bat_props,
+	.property_is_writeable	= rk817_bat_prop_writeable,
 	.num_properties = ARRAY_SIZE(rk817_bat_props),
 	.get_property = rk817_bat_get_prop,
+	.set_property = rk817_bat_set_prop,
 };
 
 static const struct power_supply_desc rk817_chg_desc = {