power: supply: bq27xxx: Add voltage_max_design property for bq270x0 and bq27x10

Report VOLTAGE_MAX_DESIGN for the bq27x00 and bq27x10 fuel gauges. Per the
datasheet, this value is stored in the Charge Termination Voltage Settings
(QV0 and QV1) of the Pack Configuration register.

Tested on the Nokia N900 with bq27200.

Signed-off-by: Sicelo A. Mhlongo <absicsz@gmail.com>
Link: https://lore.kernel.org/r/20250207211521.103357-1-absicsz@gmail.com
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

Author: sicelo

drivers/power/supply/bq27xxx_battery.c

@@ -124,6 +124,7 @@ enum bq27xxx_reg_index {
 	BQ27XXX_DM_DATA,	/* Block Data */
 	BQ27XXX_DM_CKSUM,	/* Block Data Checksum */
 	BQ27XXX_REG_SEDVF,	/* End-of-discharge Voltage */
+	BQ27XXX_REG_PKCFG,	/* Pack Configuration */
 	BQ27XXX_REG_MAX,	/* sentinel */
 };
 
@@ -161,6 +162,7 @@ static u8
 		[BQ27XXX_DM_DATA] = INVALID_REG_ADDR,
 		[BQ27XXX_DM_CKSUM] = INVALID_REG_ADDR,
 		[BQ27XXX_REG_SEDVF] = 0x77,
+		[BQ27XXX_REG_PKCFG] = 0x7C,
 	},
 	bq27010_regs[BQ27XXX_REG_MAX] = {
 		[BQ27XXX_REG_CTRL] = 0x00,
@@ -187,6 +189,7 @@ static u8
 		[BQ27XXX_DM_DATA] = INVALID_REG_ADDR,
 		[BQ27XXX_DM_CKSUM] = INVALID_REG_ADDR,
 		[BQ27XXX_REG_SEDVF] = 0x77,
+		[BQ27XXX_REG_PKCFG] = 0x7C,
 	},
 	bq2750x_regs[BQ27XXX_REG_MAX] = {
 		[BQ27XXX_REG_CTRL] = 0x00,
@@ -583,6 +586,7 @@ static enum power_supply_property bq27000_props[] = {
 	POWER_SUPPLY_PROP_HEALTH,
 	POWER_SUPPLY_PROP_MANUFACTURER,
 	POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN,
+	POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN,
 };
 
 static enum power_supply_property bq27010_props[] = {
@@ -604,6 +608,7 @@ static enum power_supply_property bq27010_props[] = {
 	POWER_SUPPLY_PROP_HEALTH,
 	POWER_SUPPLY_PROP_MANUFACTURER,
 	POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN,
+	POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN,
 };
 
 #define bq2750x_props bq27510g3_props
@@ -2044,6 +2049,35 @@ static int bq27xxx_battery_voltage(struct bq27xxx_device_info *di,
 	return 0;
 }
 
+/*
+ * Return the design maximum battery Voltage in microvolts, or < 0 if something
+ * fails. The programmed value of the maximum battery voltage is determined by
+ * QV0 and QV1 (bits 5 and 6) in the Pack Configuration register.
+ */
+static int bq27xxx_battery_read_dmax_volt(struct bq27xxx_device_info *di,
+					  union power_supply_propval *val)
+{
+	int reg_val, qv;
+
+	if (di->voltage_max_design > 0) {
+		val->intval = di->voltage_max_design;
+		return 0;
+	}
+
+	reg_val = bq27xxx_read(di, BQ27XXX_REG_PKCFG, true);
+	if (reg_val < 0) {
+		dev_err(di->dev, "error reading design max voltage\n");
+		return reg_val;
+	}
+
+	qv = (reg_val >> 5) & 0x3;
+	val->intval = 3968000 + 48000 * qv;
+
+	di->voltage_max_design = val->intval;
+
+	return 0;
+}
+
 /*
  * Return the design minimum battery Voltage in microvolts
  * Or < 0 if something fails.
@@ -2158,6 +2192,9 @@ static int bq27xxx_battery_get_property(struct power_supply *psy,
 	case POWER_SUPPLY_PROP_VOLTAGE_MIN_DESIGN:
 		ret = bq27xxx_battery_read_dmin_volt(di, val);
 		break;
+	case POWER_SUPPLY_PROP_VOLTAGE_MAX_DESIGN:
+		ret = bq27xxx_battery_read_dmax_volt(di, val);
+		break;
 	case POWER_SUPPLY_PROP_CYCLE_COUNT:
 		ret = bq27xxx_battery_read_cyct(di, val);
 		break;

include/linux/power/bq27xxx_battery.h

@@ -62,6 +62,7 @@ struct bq27xxx_device_info {
 	struct bq27xxx_reg_cache cache;
 	int charge_design_full;
 	int voltage_min_design;
+	int voltage_max_design;
 	bool removed;
 	unsigned long last_update;
 	union power_supply_propval last_status;