power: supply: ab8500: Standardize temp res lookup

The lookup from battery temperature to internal resistance was
using its own format. Rewrite this to use the table inside
struct power_supply_battery_info:s resist_table.

The supplied resistance table has to be rewritten to express
the resistance in percent of the factory resistance as a
side effect.

We can then rely on the library function
power_supply_temp2resist_simple() to interpolate the internal
resistance percent from the temperature.

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

drivers/power/supply/ab8500-bm.h

@@ -379,8 +379,6 @@ struct ab8500_maxim_parameters {
  * @r_to_t_tbl:			table containing resistance to temp points
  * @n_v_cap_tbl_elements:	number of elements in v_to_cap_tbl
  * @v_to_cap_tbl:		Voltage to capacity (in %) table
- * @n_batres_tbl_elements	number of elements in the batres_tbl
- * @batres_tbl			battery internal resistance vs temperature table
  */
 struct ab8500_battery_type {
 	int resis_high;
@@ -397,8 +395,6 @@ struct ab8500_battery_type {
 	const struct ab8500_res_to_temp *r_to_t_tbl;
 	int n_v_cap_tbl_elements;
 	const struct ab8500_v_to_cap *v_to_cap_tbl;
-	int n_batres_tbl_elements;
-	const struct batres_vs_temp *batres_tbl;
 };
 
 /**
@@ -502,17 +498,6 @@ struct res_to_temp {
 	int resist;
 };
 
-/**
- * struct batres_vs_temp - defines one point in a temp vs battery internal
- * resistance curve.
- * @temp:			battery pack temperature in Celsius
- * @resist:			battery internal reistance in mOhm
- */
-struct batres_vs_temp {
-	int temp;
-	int resist;
-};
-
 /* Forward declaration */
 struct ab8500_fg;
 

drivers/power/supply/ab8500_bmdata.c

@@ -67,16 +67,17 @@ static const struct ab8500_res_to_temp temp_tbl[] = {
 
 /*
  * Note that the batres_vs_temp table must be strictly sorted by falling
- * temperature values to work.
+ * temperature values to work. Factory resistance is 300 mOhm and the
+ * resistance values to the right are percentages of 300 mOhm.
  */
-static const struct batres_vs_temp temp_to_batres_tbl_thermistor[] = {
-	{ 40, 120},
-	{ 30, 135},
-	{ 20, 165},
-	{ 10, 230},
-	{ 00, 325},
-	{-10, 445},
-	{-20, 595},
+static struct power_supply_resistance_temp_table temp_to_batres_tbl_thermistor[] = {
+	{ .temp = 40, .resistance = 40 /* 120 mOhm */ },
+	{ .temp = 30, .resistance = 45 /* 135 mOhm */ },
+	{ .temp = 20, .resistance = 55 /* 165 mOhm */ },
+	{ .temp = 10, .resistance = 77 /* 230 mOhm */ },
+	{ .temp = 00, .resistance = 108 /* 325 mOhm */ },
+	{ .temp = -10, .resistance = 158 /* 445 mOhm */ },
+	{ .temp = -20, .resistance = 198 /* 595 mOhm */ },
 };
 
 /* Default battery type for reference designs is the unknown type */
@@ -95,8 +96,6 @@ static struct ab8500_battery_type bat_type_thermistor_unknown = {
 	.r_to_t_tbl = temp_tbl,
 	.n_v_cap_tbl_elements = ARRAY_SIZE(cap_tbl),
 	.v_to_cap_tbl = cap_tbl,
-	.n_batres_tbl_elements = ARRAY_SIZE(temp_to_batres_tbl_thermistor),
-	.batres_tbl = temp_to_batres_tbl_thermistor,
 };
 
 static const struct ab8500_bm_capacity_levels cap_levels = {
@@ -209,8 +208,16 @@ int ab8500_bm_of_probe(struct power_supply *psy,
 		/* Charging stops when we drop below this current */
 		bi->charge_term_current_ua = 200000;
 
-	if (bi->factory_internal_resistance_uohm < 0)
+	/*
+	 * Internal resistance and factory resistance are tightly coupled
+	 * so both MUST be defined or we fall back to defaults.
+	 */
+	if ((bi->factory_internal_resistance_uohm < 0) ||
+	    !bi->resist_table) {
 		bi->factory_internal_resistance_uohm = 300000;
+		bi->resist_table = temp_to_batres_tbl_thermistor;
+		bi->resist_table_size = ARRAY_SIZE(temp_to_batres_tbl_thermistor);
+	}
 
 	if (bi->temp_min == INT_MIN)
 		bi->temp_min = AB8500_TEMP_UNDER;

drivers/power/supply/ab8500_fg.c

@@ -901,44 +901,35 @@ static int ab8500_fg_uncomp_volt_to_capacity(struct ab8500_fg *di)
  * @di:		pointer to the ab8500_fg structure
  *
  * 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.
+ * 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)
 {
-	int i, tbl_size;
-	const struct batres_vs_temp *tbl;
-	int resist = 0;
-
-	tbl = di->bm->bat_type->batres_tbl;
-	tbl_size = di->bm->bat_type->n_batres_tbl_elements;
-
-	for (i = 0; i < tbl_size; ++i) {
-		if (di->bat_temp / 10 > tbl[i].temp)
-			break;
-	}
+	struct power_supply_battery_info *bi = &di->bm->bi;
+	int resistance_percent = 0;
+	int resistance;
 
-	if ((i > 0) && (i < tbl_size)) {
-		resist = fixp_linear_interpolate(
-			tbl[i].temp,
-			tbl[i].resist,
-			tbl[i-1].temp,
-			tbl[i-1].resist,
-			di->bat_temp / 10);
-	} else if (i == 0) {
-		resist = tbl[0].resist;
-	} else {
-		resist = tbl[tbl_size - 1].resist;
-	}
+	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.
+	 */
+	resistance = (bi->factory_internal_resistance_uohm / 1000);
+	resistance = resistance * resistance_percent / 100;
 
 	dev_dbg(di->dev, "%s Temp: %d battery internal resistance: %d"
 	    " fg resistance %d, total: %d (mOhm)\n",
-		__func__, di->bat_temp, resist, di->bm->fg_res / 10,
-		(di->bm->fg_res / 10) + resist);
+		__func__, di->bat_temp, resistance, di->bm->fg_res / 10,
+		(di->bm->fg_res / 10) + resistance);
 
 	/* fg_res variable is in 0.1mOhm */
-	resist += di->bm->fg_res / 10;
+	resistance += di->bm->fg_res / 10;
 
-	return resist;
+	return resistance;
 }
 
 /**