power: supply: ab8500_fg: Use VBAT-to-Ri if possible

Augment the AB8500 fuel gauge to use the VBAT-to-Ri method of
estimating the internal resistance if possible. Else fall back
to using the temperature-to-Ri or just the default Ri.

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

diff --git a/drivers/power/supply/ab8500_fg.c b/drivers/power/supply/ab8500_fg.c
index f2ff310..1abe10c 100644 (file)
--- a/drivers/power/supply/ab8500_fg.c
+++ b/drivers/power/supply/ab8500_fg.c
@@ -877,27 +877,38 @@ static int ab8500_fg_uncomp_volt_to_capacity(struct ab8500_fg *di)
 /**
  * ab8500_fg_battery_resistance() - Returns the battery inner resistance
  * @di:                pointer to the ab8500_fg structure
+ * @vbat_uncomp_uv: Uncompensated VBAT voltage
  *
  * Returns battery inner resistance added with the fuel gauge resistor value
  * to get the total resistance in the whole link from gnd to bat+ node
  * in milliohm.
  */
-static int ab8500_fg_battery_resistance(struct ab8500_fg *di)
+static int ab8500_fg_battery_resistance(struct ab8500_fg *di, int vbat_uncomp_uv)
 {
        struct power_supply_battery_info *bi = di->bm->bi;
        int resistance_percent = 0;
        int resistance;
 
-       resistance_percent = power_supply_temp2resist_simple(bi->resist_table,
-                                                bi->resist_table_size,
-                                                di->bat_temp / 10);
        /*
-        * We get a percentage of factory resistance here so first get
-        * the factory resistance in milliohms then calculate how much
-        * resistance we have at this temperature.
+        * Determine the resistance at this voltage. First try VBAT-to-Ri else
+        * just infer it from the surrounding temperature, if nothing works just
+        * use the internal resistance.
         */
-       resistance = (bi->factory_internal_resistance_uohm / 1000);
-       resistance = resistance * resistance_percent / 100;
+       if (power_supply_supports_vbat2ri(bi)) {
+               resistance = power_supply_vbat2ri(bi, vbat_uncomp_uv, di->flags.charging);
+               /* Convert to milliohm */
+               resistance = resistance / 1000;
+       } else if (power_supply_supports_temp2ri(bi)) {
+               resistance_percent = power_supply_temp2resist_simple(bi->resist_table,
+                                                                    bi->resist_table_size,
+                                                                    di->bat_temp / 10);
+               /* Convert to milliohm */
+               resistance = bi->factory_internal_resistance_uohm / 1000;
+               resistance = resistance * resistance_percent / 100;
+       } else {
+               /* Last fallback */
+               resistance = bi->factory_internal_resistance_uohm / 1000;
+       }
 
        dev_dbg(di->dev, "%s Temp: %d battery internal resistance: %d"
            " fg resistance %d, total: %d (mOhm)\n",
@@ -955,7 +966,7 @@ static int ab8500_load_comp_fg_bat_voltage(struct ab8500_fg *di, bool always)
        vbat_uv = vbat_uv / i;
 
        /* Next we apply voltage compensation from internal resistance */
-       rcomp = ab8500_fg_battery_resistance(di);
+       rcomp = ab8500_fg_battery_resistance(di, vbat_uv);
        vbat_uv = vbat_uv - (di->inst_curr_ua * rcomp) / 1000;
 
        /* Always keep this state at latest measurement */