power: supply: core: Add some helpers to use the battery OCV capacity table

We have introduced some battery properties to present the OCV table
temperatures and OCV capacity table values. Thus this patch add OCV
temperature and OCV table for battery information, as well as providing
some helper functions to use the OCV capacity table for users.
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/power_supply_core.c

@@ -570,7 +570,7 @@ int power_supply_get_battery_info(struct power_supply *psy,
 {
 	struct device_node *battery_np;
 	const char *value;
-	int err;
+	int err, len, index;
 
 	info->energy_full_design_uwh         = -EINVAL;
 	info->charge_full_design_uah         = -EINVAL;
@@ -581,6 +581,12 @@ int power_supply_get_battery_info(struct power_supply *psy,
 	info->constant_charge_voltage_max_uv = -EINVAL;
 	info->factory_internal_resistance_uohm  = -EINVAL;
 
+	for (index = 0; index < POWER_SUPPLY_OCV_TEMP_MAX; index++) {
+		info->ocv_table[index]       = NULL;
+		info->ocv_temp[index]        = -EINVAL;
+		info->ocv_table_size[index]  = -EINVAL;
+	}
+
 	if (!psy->of_node) {
 		dev_warn(&psy->dev, "%s currently only supports devicetree\n",
 			 __func__);
@@ -620,10 +626,139 @@ int power_supply_get_battery_info(struct power_supply *psy,
 	of_property_read_u32(battery_np, "factory-internal-resistance-micro-ohms",
 			     &info->factory_internal_resistance_uohm);
 
+	len = of_property_count_u32_elems(battery_np, "ocv-capacity-celsius");
+	if (len < 0 && len != -EINVAL) {
+		return len;
+	} else if (len > POWER_SUPPLY_OCV_TEMP_MAX) {
+		dev_err(&psy->dev, "Too many temperature values\n");
+		return -EINVAL;
+	} else if (len > 0) {
+		of_property_read_u32_array(battery_np, "ocv-capacity-celsius",
+					   info->ocv_temp, len);
+	}
+
+	for (index = 0; index < len; index++) {
+		struct power_supply_battery_ocv_table *table;
+		char *propname;
+		const __be32 *list;
+		int i, tab_len, size;
+
+		propname = kasprintf(GFP_KERNEL, "ocv-capacity-table-%d", index);
+		list = of_get_property(battery_np, propname, &size);
+		if (!list || !size) {
+			dev_err(&psy->dev, "failed to get %s\n", propname);
+			kfree(propname);
+			power_supply_put_battery_info(psy, info);
+			return -EINVAL;
+		}
+
+		kfree(propname);
+		tab_len = size / (2 * sizeof(__be32));
+		info->ocv_table_size[index] = tab_len;
+
+		table = info->ocv_table[index] =
+			devm_kcalloc(&psy->dev, tab_len, sizeof(*table), GFP_KERNEL);
+		if (!info->ocv_table[index]) {
+			power_supply_put_battery_info(psy, info);
+			return -ENOMEM;
+		}
+
+		for (i = 0; i < tab_len; i++) {
+			table[i].ocv = be32_to_cpu(*list++);
+			table[i].capacity = be32_to_cpu(*list++);
+		}
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(power_supply_get_battery_info);
 
+void power_supply_put_battery_info(struct power_supply *psy,
+				   struct power_supply_battery_info *info)
+{
+	int i;
+
+	for (i = 0; i < POWER_SUPPLY_OCV_TEMP_MAX; i++) {
+		if (info->ocv_table[i])
+			devm_kfree(&psy->dev, info->ocv_table[i]);
+	}
+}
+EXPORT_SYMBOL_GPL(power_supply_put_battery_info);
+
+/**
+ * power_supply_ocv2cap_simple() - find the battery capacity
+ * @table: Pointer to battery OCV lookup table
+ * @table_len: OCV table length
+ * @ocv: Current OCV value
+ *
+ * This helper function is used to look up battery capacity according to
+ * current OCV value from one OCV table, and the OCV table must be ordered
+ * descending.
+ *
+ * Return: the battery capacity.
+ */
+int power_supply_ocv2cap_simple(struct power_supply_battery_ocv_table *table,
+				int table_len, int ocv)
+{
+	int i, cap, tmp;
+
+	for (i = 0; i < table_len; i++)
+		if (ocv > table[i].ocv)
+			break;
+
+	if (i > 0 && i < table_len) {
+		tmp = (table[i - 1].capacity - table[i].capacity) *
+			(ocv - table[i].ocv);
+		tmp /= table[i - 1].ocv - table[i].ocv;
+		cap = tmp + table[i].capacity;
+	} else if (i == 0) {
+		cap = table[0].capacity;
+	} else {
+		cap = table[table_len - 1].capacity;
+	}
+
+	return cap;
+}
+EXPORT_SYMBOL_GPL(power_supply_ocv2cap_simple);
+
+struct power_supply_battery_ocv_table *
+power_supply_find_ocv2cap_table(struct power_supply_battery_info *info,
+				int temp, int *table_len)
+{
+	int best_temp_diff = INT_MAX, temp_diff;
+	u8 i, best_index = 0;
+
+	if (!info->ocv_table[0])
+		return NULL;
+
+	for (i = 0; i < POWER_SUPPLY_OCV_TEMP_MAX; i++) {
+		temp_diff = abs(info->ocv_temp[i] - temp);
+
+		if (temp_diff < best_temp_diff) {
+			best_temp_diff = temp_diff;
+			best_index = i;
+		}
+	}
+
+	*table_len = info->ocv_table_size[best_index];
+	return info->ocv_table[best_index];
+}
+EXPORT_SYMBOL_GPL(power_supply_find_ocv2cap_table);
+
+int power_supply_batinfo_ocv2cap(struct power_supply_battery_info *info,
+				 int ocv, int temp)
+{
+	struct power_supply_battery_ocv_table *table;
+	int table_len;
+
+	table = power_supply_find_ocv2cap_table(info, temp, &table_len);
+	if (!table)
+		return -EINVAL;
+
+	return power_supply_ocv2cap_simple(table, table_len, ocv);
+}
+EXPORT_SYMBOL_GPL(power_supply_batinfo_ocv2cap);
+
 int power_supply_get_property(struct power_supply *psy,
 			    enum power_supply_property psp,
 			    union power_supply_propval *val)

include/linux/power_supply.h

@@ -309,6 +309,13 @@ struct power_supply_info {
 	int use_for_apm;
 };
 
+struct power_supply_battery_ocv_table {
+	int ocv;	/* microVolts */
+	int capacity;	/* percent */
+};
+
+#define POWER_SUPPLY_OCV_TEMP_MAX 20
+
 /*
  * This is the recommended struct to manage static battery parameters,
  * populated by power_supply_get_battery_info(). Most platform drivers should
@@ -327,6 +334,9 @@ struct power_supply_battery_info {
 	int constant_charge_current_max_ua; /* microAmps */
 	int constant_charge_voltage_max_uv; /* microVolts */
 	int factory_internal_resistance_uohm;   /* microOhms */
+	int ocv_temp[POWER_SUPPLY_OCV_TEMP_MAX];/* celsius */
+	struct power_supply_battery_ocv_table *ocv_table[POWER_SUPPLY_OCV_TEMP_MAX];
+	int ocv_table_size[POWER_SUPPLY_OCV_TEMP_MAX];
 };
 
 extern struct atomic_notifier_head power_supply_notifier;
@@ -350,6 +360,15 @@ devm_power_supply_get_by_phandle(struct device *dev, const char *property)
 
 extern int power_supply_get_battery_info(struct power_supply *psy,
 					 struct power_supply_battery_info *info);
+extern void power_supply_put_battery_info(struct power_supply *psy,
+					  struct power_supply_battery_info *info);
+extern int power_supply_ocv2cap_simple(struct power_supply_battery_ocv_table *table,
+				       int table_len, int ocv);
+extern struct power_supply_battery_ocv_table *
+power_supply_find_ocv2cap_table(struct power_supply_battery_info *info,
+				int temp, int *table_len);
+extern int power_supply_batinfo_ocv2cap(struct power_supply_battery_info *info,
+					int ocv, int temp);
 extern void power_supply_changed(struct power_supply *psy);
 extern int power_supply_am_i_supplied(struct power_supply *psy);
 extern int power_supply_set_input_current_limit_from_supplier(