power: supply: ab8500: Standardize BTI resistance

Al Stone · Al Stone · commit 37fe599d11f7 · 2022-12-14T18:19:00.000-07:00
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2071846 Tested: This is one of a series of patch sets to enable Arm SystemReady IR support in the kernel for NXP i.MX8 platforms. This set updates the power subsystem. This set has been tested via simple boot tests and the CI loop. Conflicts: drivers/power/supply/ab8500-bm.h drivers/power/supply/ab8500_bmdata.c drivers/power/supply/ab8500_btemp.c drivers/power/supply/ab8500_fg.c This is not a supported device so these parts of the patch have been dropped. commit 1f918e0 Author: Linus Walleij <linus.walleij@linaro.org> Date: Sat Feb 26 00:27:57 2022 +0100 power: supply: ab8500: Standardize BTI resistance The Battery Type Indicator (BTI) resistor is a resistor mounted between a special terminal on the battery and ground. By sending a fixed current (such as 7mA) through this resistor and measuring the voltage over it, the resistance can be determined, and this verifies the battery type. Typical side view of the battery: o o o GND BTI +3.8V Typical example of the electrical layout: +3.8 V BTI | | | + | _______ [ ] 7kOhm ___ | | | | | GND GND By verifying this resistance before attempting to charge the battery we add an additional level of security. In some systems this is used for plug-and-play of batteries with different capacity. In other cases, this is merely used to verify that the right type of battery is connected, if several batteries have the same physical shape and can be plugged into the same slot. Sometimes this is just a surplus security mechanism. Nokia and Samsung among many other vendors are known to use these BTI resistors. Add the BTI properties to struct power_supply_battery_info and switch the AB8500 charger code over to using it. Signed-off-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com> (cherry picked from commit 1f918e0) Signed-off-by: Al Stone <ahs3@redhat.com>
diff --git a/drivers/power/supply/ab8500_btemp.c b/drivers/power/supply/ab8500_btemp.c
@@ -31,7 +31,6 @@
 #include "ab8500-bm.h"
 
 #define VTVOUT_V			1800
-
 #define BTEMP_THERMAL_LOW_LIMIT		-10
 #define BTEMP_THERMAL_MED_LIMIT		0
 #define BTEMP_THERMAL_HIGH_LIMIT_52	52
@@ -135,7 +134,6 @@ static int ab8500_btemp_batctrl_volt_to_res(struct ab8500_btemp *di,
 	int v_batctrl, int inst_curr)
 {
 	int rbs;
-
 	if (is_ab8500_1p1_or_earlier(di->parent)) {
 		/*
 		 * For ABB cut1.0 and 1.1 BAT_CTRL is internally
@@ -153,10 +151,10 @@ static int ab8500_btemp_batctrl_volt_to_res(struct ab8500_btemp *di,
 		       - di->bm->gnd_lift_resistance * inst_curr)
 		      / di->curr_source;
 	} else {
-		/*
-		 * BAT_CTRL is internally
-		 * connected to 1.8V through a 80k resistor
-		 */
+	/*
+	 * BAT_CTRL is internally
+	 * connected to 1.8V through a 80k resistor
+	 */
 		rbs = (80000 * (v_batctrl)) / (1800 - v_batctrl);
 	}
 
@@ -358,7 +356,6 @@ static int ab8500_btemp_get_batctrl_res(struct ab8500_btemp *di)
 		dev_err(di->dev, "%s curr source enabled failed\n", __func__);
 		return ret;
 	}
-
 	if (!di->fg)
 		di->fg = ab8500_fg_get();
 	if (!di->fg) {
@@ -399,7 +396,6 @@ static int ab8500_btemp_get_batctrl_res(struct ab8500_btemp *di)
 		dev_err(di->dev, "%s curr source disable failed\n", __func__);
 		return ret;
 	}
-
 	dev_dbg(di->dev, "%s batctrl: %d res: %d inst_curr: %d samples: %d\n",
 		__func__, batctrl, res, inst_curr, i);
 
@@ -574,6 +570,7 @@ static void ab8500_btemp_periodic_work(struct work_struct *work)
 	}
 
 	bat_temp = ab8500_btemp_measure_temp(di);
+
 	/*
 	 * Filter battery temperature.
 	 * Allow direct updates on temperature only if two samples result in
diff --git a/drivers/power/supply/ab8500_fg.c b/drivers/power/supply/ab8500_fg.c
@@ -1077,7 +1077,7 @@ static int ab8500_fg_calc_cap_discharge_voltage(struct ab8500_fg *di, bool comp)
 	int permille, mah;
 
 	if (comp)
-		permille = ab8500_fg_load_comp_volt_to_capacity(di);
+	permille = ab8500_fg_load_comp_volt_to_capacity(di);
 	else
 		permille = ab8500_fg_uncomp_volt_to_capacity(di);
 
diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
@@ -607,7 +607,9 @@ int power_supply_get_battery_info(struct power_supply *psy,
 	info->temp_min                       = INT_MIN;
 	info->temp_max                       = INT_MAX;
 	info->factory_internal_resistance_uohm  = -EINVAL;
-	info->resist_table = NULL;
+	info->resist_table                   = NULL;
+	info->bti_resistance_ohm             = -EINVAL;
+	info->bti_resistance_tolerance       = -EINVAL;
 
 	for (index = 0; index < POWER_SUPPLY_OCV_TEMP_MAX; index++) {
 		info->ocv_table[index]       = NULL;
@@ -938,6 +940,28 @@ int power_supply_batinfo_ocv2cap(struct power_supply_battery_info *info,
 }
 EXPORT_SYMBOL_GPL(power_supply_batinfo_ocv2cap);
 
+bool power_supply_battery_bti_in_range(struct power_supply_battery_info *info,
+				       int resistance)
+{
+	int low, high;
+
+	/* Nothing like this can be checked */
+	if (info->bti_resistance_ohm <= 0)
+		return false;
+
+	/* This will be extremely strict and unlikely to work */
+	if (info->bti_resistance_tolerance <= 0)
+		return (info->bti_resistance_ohm == resistance);
+
+	low = info->bti_resistance_ohm -
+		(info->bti_resistance_ohm * info->bti_resistance_tolerance) / 100;
+	high = info->bti_resistance_ohm +
+		(info->bti_resistance_ohm * info->bti_resistance_tolerance) / 100;
+
+	return ((resistance >= low) && (resistance <= high));
+}
+EXPORT_SYMBOL_GPL(power_supply_battery_bti_in_range);
+
 int power_supply_get_property(struct power_supply *psy,
 			    enum power_supply_property psp,
 			    union power_supply_propval *val)
diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
@@ -498,6 +498,14 @@ struct power_supply_maintenance_charge_table {
  *   by temperature: highest temperature with lowest resistance first, lowest
  *   temperature with highest resistance last.
  * @resist_table_size: the number of items in the resist_table.
+ * @bti_resistance_ohm: The Battery Type Indicator (BIT) nominal resistance
+ *   in ohms for this battery, if an identification resistor is mounted
+ *   between a third battery terminal and ground. This scheme is used by a lot
+ *   of mobile device batteries.
+ * @bti_resistance_tolerance: The tolerance in percent of the BTI resistance,
+ *   for example 10 for +/- 10%, if the bti_resistance is set to 7000 and the
+ *   tolerance is 10% we will detect a proper battery if the BTI resistance
+ *   is between 6300 and 7700 Ohm.
  *
  * This is the recommended struct to manage static battery parameters,
  * populated by power_supply_get_battery_info(). Most platform drivers should
@@ -624,6 +632,8 @@ struct power_supply_battery_info {
 	int ocv_table_size[POWER_SUPPLY_OCV_TEMP_MAX];
 	struct power_supply_resistance_temp_table *resist_table;
 	int resist_table_size;
+	int bti_resistance_ohm;
+	int bti_resistance_tolerance;
 };
 
 extern struct atomic_notifier_head power_supply_notifier;
@@ -667,6 +677,8 @@ power_supply_temp2resist_simple(struct power_supply_resistance_temp_table *table
 				int table_len, int temp);
 extern struct power_supply_maintenance_charge_table *
 power_supply_get_maintenance_charging_setting(struct power_supply_battery_info *info, int index);
+extern bool power_supply_battery_bti_in_range(struct power_supply_battery_info *info,
+					      int resistance);
 extern void power_supply_changed(struct power_supply *psy);
 extern int power_supply_am_i_supplied(struct power_supply *psy);
 int power_supply_get_property_from_supplier(struct power_supply *psy,
@@ -684,6 +696,7 @@ power_supply_supports_maintenance_charging(struct power_supply_battery_info *inf
 	return (mt != NULL);
 }
 
+
 #ifdef CONFIG_POWER_SUPPLY
 extern int power_supply_is_system_supplied(void);
 #else
