Improve the SC27XX fuel gauge controller

index 5c36c43..1a9a9fa 100644
@@ -565,9 +565,11 @@ struct power_supply *devm_power_supply_get_by_phandle(struct device *dev,
 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;

@@ -692,10 +714,53 @@ 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
  * @table_len: OCV table length

index 28413f7..dcd5a71 100644
@@ -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 @@ extern int power_supply_ocv2cap_simple(struct power_supply_battery_ocv_table *ta
 				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(

index bc8f5bd..221b6fb 100644
@@ -81,9 +81,11 @@
  * @max_volt: the maximum constant input voltage in millivolt
  * @min_volt: the minimum drained battery voltage in microvolt
  * @table_len: the capacity table length
+ * @resist_table_len: the resistance table length
  * @cur_1000ma_adc: ADC value corresponding to 1000 mA
  * @vol_1000mv_adc: ADC value corresponding to 1000 mV
  * @cap_table: capacity table with corresponding ocv
+ * @resist_table: resistance percent table with corresponding temperature
  */
 struct sc27xx_fgu_data {
 	struct regmap *regmap;

@@ -103,15 +105,18 @@ struct sc27xx_fgu_data {
 	int max_volt;
 	int min_volt;
 	int table_len;
+	int resist_table_len;
 	int cur_1000ma_adc;
 	int vol_1000mv_adc;
 	struct power_supply_battery_ocv_table *cap_table;
+	struct power_supply_resistance_temp_table *resist_table;
 };
 
 static int sc27xx_fgu_cap_to_clbcnt(struct sc27xx_fgu_data *data, int capacity);
 static void sc27xx_fgu_capacity_calibration(struct sc27xx_fgu_data *data,
 					    int cap, bool int_mode);
 static void sc27xx_fgu_adjust_cap(struct sc27xx_fgu_data *data, int cap);
+static int sc27xx_fgu_get_temp(struct sc27xx_fgu_data *data, int *temp);
 
 static const char * const sc27xx_charger_supply_name[] = {
 	"sc2731_charger",

@@ -434,7 +439,7 @@ static int sc27xx_fgu_get_current(struct sc27xx_fgu_data *data, int *val)
 
 static int sc27xx_fgu_get_vbat_ocv(struct sc27xx_fgu_data *data, int *val)
 {
-	int vol, cur, ret;
+	int vol, cur, ret, temp, resistance;
 
 	ret = sc27xx_fgu_get_vbat_vol(data, &vol);
 	if (ret)

@@ -444,8 +449,19 @@ static int sc27xx_fgu_get_vbat_ocv(struct sc27xx_fgu_data *data, int *val)
 	if (ret)
 		return ret;
 
+	resistance = data->internal_resist;
+	if (data->resist_table_len > 0) {
+		ret = sc27xx_fgu_get_temp(data, &temp);
+		if (ret)
+			return ret;
+
+		resistance = power_supply_temp2resist_simple(data->resist_table,
+						data->resist_table_len, temp);
+		resistance = data->internal_resist * resistance / 100;
+	}
+
 	/* Return the battery OCV in micro volts. */
-	*val = vol * 1000 - cur * data->internal_resist;
+	*val = vol * 1000 - cur * resistance;
 
 	return 0;
 }

@@ -929,6 +945,18 @@ static int sc27xx_fgu_hw_init(struct sc27xx_fgu_data *data)
 	if (!data->alarm_cap)
 		data->alarm_cap += 1;
 
+	data->resist_table_len = info.resist_table_size;
+	if (data->resist_table_len > 0) {
+		data->resist_table = devm_kmemdup(data->dev, info.resist_table,
+						  data->resist_table_len *
+						  sizeof(struct power_supply_resistance_temp_table),
+						  GFP_KERNEL);
+		if (!data->resist_table) {
+			power_supply_put_battery_info(data->battery, &info);
+			return -ENOMEM;
+		}
+	}
+
 	power_supply_put_battery_info(data->battery, &info);
 
 	ret = sc27xx_fgu_calibration(data);

index 221b6fb..f363fa7 100644
@@ -62,6 +62,8 @@
 
 #define SC27XX_FGU_CUR_BASIC_ADC	8192
 #define SC27XX_FGU_SAMPLE_HZ		2
+/* micro Ohms */
+#define SC27XX_FGU_IDEAL_RESISTANCE	20000
 
 /*
  * struct sc27xx_fgu_data: describe the FGU device

@@ -84,6 +86,7 @@
  * @resist_table_len: the resistance table length
  * @cur_1000ma_adc: ADC value corresponding to 1000 mA
  * @vol_1000mv_adc: ADC value corresponding to 1000 mV
+ * @calib_resist: the real resistance of coulomb counter chip in mOhm
  * @cap_table: capacity table with corresponding ocv
  * @resist_table: resistance percent table with corresponding temperature
  */

@@ -108,6 +111,7 @@ struct sc27xx_fgu_data {
 	int resist_table_len;
 	int cur_1000ma_adc;
 	int vol_1000mv_adc;
+	int calib_resist;
 	struct power_supply_battery_ocv_table *cap_table;
 	struct power_supply_resistance_temp_table *resist_table;
 };

@@ -900,7 +904,9 @@ static int sc27xx_fgu_calibration(struct sc27xx_fgu_data *data)
 	 */
 	cal_4200mv = (calib_data & 0x1ff) + 6963 - 4096 - 256;
 	data->vol_1000mv_adc = DIV_ROUND_CLOSEST(cal_4200mv * 10, 42);
-	data->cur_1000ma_adc = data->vol_1000mv_adc * 4;
+	data->cur_1000ma_adc =
+		DIV_ROUND_CLOSEST(data->vol_1000mv_adc * 4 * data->calib_resist,
+				  SC27XX_FGU_IDEAL_RESISTANCE);
 
 	kfree(buf);
 	return 0;

@@ -1079,6 +1085,15 @@ static int sc27xx_fgu_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	ret = device_property_read_u32(&pdev->dev,
+				       "sprd,calib-resistance",
+				       &data->calib_resist);
+	if (ret) {
+		dev_err(&pdev->dev,
+			"failed to get fgu calibration resistance\n");
+		return ret;
+	}
+
 	data->channel = devm_iio_channel_get(dev, "bat-temp");
 	if (IS_ERR(data->channel)) {
 		dev_err(dev, "failed to get IIO channel\n");