power: supply: ab8500_fg: Account for line impedance

We add the line impedance to the inner resistance determined
from the battery voltage or other means to improve the
capacity estimations.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

Author: Linus Walleij

drivers/power/supply/ab8500_fg.c

@@ -213,6 +213,7 @@ struct ab8500_fg {
 	int init_cnt;
 	int low_bat_cnt;
 	int nbr_cceoc_irq_cnt;
+	u32 line_impedance_uohm;
 	bool recovery_needed;
 	bool high_curr_mode;
 	bool init_capacity;
@@ -910,6 +911,9 @@ static int ab8500_fg_battery_resistance(struct ab8500_fg *di, int vbat_uncomp_uv
 		resistance = bi->factory_internal_resistance_uohm / 1000;
 	}
 
+	/* Compensate for line impedance */
+	resistance += (di->line_impedance_uohm / 1000);
+
 	dev_dbg(di->dev, "%s Temp: %d battery internal resistance: %d"
 	    " fg resistance %d, total: %d (mOhm)\n",
 		__func__, di->bat_temp, resistance, di->bm->fg_res / 10,
@@ -3098,6 +3102,11 @@ static int ab8500_fg_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	if (!of_property_read_u32(dev->of_node, "line-impedance-micro-ohms",
+				  &di->line_impedance_uohm))
+		dev_info(dev, "line impedance: %u uOhm\n",
+			 di->line_impedance_uohm);
+
 	psy_cfg.supplied_to = supply_interface;
 	psy_cfg.num_supplicants = ARRAY_SIZE(supply_interface);
 	psy_cfg.drv_data = di;