power: supply: core: Add battery internal resistance temperature table support

Since the battery internal resistance can be changed with the temperature
changes, thus add a resistance temperature table support to look up
the accurate battery internal resistance in a certain temperature.
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Baolin Wang <baolin.wang7@gmail.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/power_supply_core.c

@@ -565,9 +565,11 @@ EXPORT_SYMBOL_GPL(devm_power_supply_get_by_phandle);
 int power_supply_get_battery_info(struct power_supply *psy,
 				  struct power_supply_battery_info *info)
 {
+	struct power_supply_resistance_temp_table *resist_table;
 	struct device_node *battery_np;
 	const char *value;
 	int err, len, index;
+	const __be32 *list;
 
 	info->energy_full_design_uwh         = -EINVAL;
 	info->charge_full_design_uah         = -EINVAL;
@@ -578,6 +580,7 @@ int power_supply_get_battery_info(struct power_supply *psy,
 	info->constant_charge_current_max_ua = -EINVAL;
 	info->constant_charge_voltage_max_uv = -EINVAL;
 	info->factory_internal_resistance_uohm  = -EINVAL;
+	info->resist_table = NULL;
 
 	for (index = 0; index < POWER_SUPPLY_OCV_TEMP_MAX; index++) {
 		info->ocv_table[index]       = NULL;
@@ -644,7 +647,6 @@ int power_supply_get_battery_info(struct power_supply *psy,
 	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);
@@ -677,6 +679,26 @@ int power_supply_get_battery_info(struct power_supply *psy,
 		}
 	}
 
+	list = of_get_property(battery_np, "resistance-temp-table", &len);
+	if (!list || !len)
+		goto out_put_node;
+
+	info->resist_table_size = len / (2 * sizeof(__be32));
+	resist_table = info->resist_table = devm_kcalloc(&psy->dev,
+							 info->resist_table_size,
+							 sizeof(*resist_table),
+							 GFP_KERNEL);
+	if (!info->resist_table) {
+		power_supply_put_battery_info(psy, info);
+		err = -ENOMEM;
+		goto out_put_node;
+	}
+
+	for (index = 0; index < info->resist_table_size; index++) {
+		resist_table[index].temp = be32_to_cpu(*list++);
+		resist_table[index].resistance = be32_to_cpu(*list++);
+	}
+
 out_put_node:
 	of_node_put(battery_np);
 	return err;
@@ -692,9 +714,52 @@ void power_supply_put_battery_info(struct power_supply *psy,
 		if (info->ocv_table[i])
 			devm_kfree(&psy->dev, info->ocv_table[i]);
 	}
+
+	if (info->resist_table)
+		devm_kfree(&psy->dev, info->resist_table);
 }
 EXPORT_SYMBOL_GPL(power_supply_put_battery_info);
 
+/**
+ * power_supply_temp2resist_simple() - find the battery internal resistance
+ * percent
+ * @table: Pointer to battery resistance temperature table
+ * @table_len: The table length
+ * @ocv: Current temperature
+ *
+ * This helper function is used to look up battery internal resistance percent
+ * according to current temperature value from the resistance temperature table,
+ * and the table must be ordered descending. Then the actual battery internal
+ * resistance = the ideal battery internal resistance * percent / 100.
+ *
+ * Return: the battery internal resistance percent
+ */
+int power_supply_temp2resist_simple(struct power_supply_resistance_temp_table *table,
+				    int table_len, int temp)
+{
+	int i, resist;
+
+	for (i = 0; i < table_len; i++)
+		if (temp > table[i].temp)
+			break;
+
+	if (i > 0 && i < table_len) {
+		int tmp;
+
+		tmp = (table[i - 1].resistance - table[i].resistance) *
+			(temp - table[i].temp);
+		tmp /= table[i - 1].temp - table[i].temp;
+		resist = tmp + table[i].resistance;
+	} else if (i == 0) {
+		resist = table[0].resistance;
+	} else {
+		resist = table[table_len - 1].resistance;
+	}
+
+	return resist;
+}
+EXPORT_SYMBOL_GPL(power_supply_temp2resist_simple);
+
 /**
  * power_supply_ocv2cap_simple() - find the battery capacity
  * @table: Pointer to battery OCV lookup table

include/linux/power_supply.h

@@ -325,6 +325,11 @@ struct power_supply_battery_ocv_table {
 	int capacity;	/* percent */
 };
 
+struct power_supply_resistance_temp_table {
+	int temp;	/* celsius */
+	int resistance;	/* internal resistance percent */
+};
+
 #define POWER_SUPPLY_OCV_TEMP_MAX 20
 
 /*
@@ -349,6 +354,8 @@ struct power_supply_battery_info {
 	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];
+	struct power_supply_resistance_temp_table *resist_table;
+	int resist_table_size;
 };
 
 extern struct atomic_notifier_head power_supply_notifier;
@@ -381,6 +388,9 @@ 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 int
+power_supply_temp2resist_simple(struct power_supply_resistance_temp_table *table,
+				int table_len, 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(