Cleanup: battery

Tidy code.  No functional changes.

BUG=chrome-os-partner:15579
BRANCH=none
TEST=discharge battery, then plug AC in and make sure it charges

Change-Id: I4cff018940ecb665be96655d6722f74dd6674f6d
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/36359

2 files changed, 48 insertions, 54 deletions

diff --git a/common/battery_link.c b/common/battery_link.c
index 2a524dea38..ba394eb51f 100644
--- a/common/battery_link.c
+++ b/common/battery_link.c
@@ -7,19 +7,14 @@
 
 #include "battery_pack.h"
 
-/* Design capacity
+/*
+ * Design capacity
  *   Battery capacity = 8200 mAh
  *   1C = 8200 mA
  */
-#define C     8200
-#define C_001 (int)(C * 0.01)
-/*
- * Common charging currents:
- *   #define C_01  (int)(C * 0.1) ==  820mA
- *   #define C_02  (int)(C * 0.2) == 1640mA
- *   #define C_05  (int)(C * 0.5) == 4100mA
- *   #define C_07  (int)(C * 0.7) == 5740mA
- */
+#define DESIGN_CAPACITY 8200
+
+#define CELSIUS_TO_DECI_KELVIN(temp_c) ((temp_c) * 10 + 2731)
 
 enum {
 	TEMP_RANGE_10,
@@ -37,7 +32,8 @@ enum {
 	VOLT_RANGE_MAX
 };
 
-/* Vendor provided charging method
+/*
+ * Vendor provided charging method
  *      temp  : < 7.2V, 7.2V ~ 8.0V, 8.0V ~ 8.4V
  *  -  0 ~ 10 :  0.8A       1.6A         0.8A
  *  - 10 ~ 23 :  1.6A       4.0A         1.6A
@@ -54,7 +50,8 @@ static const int const current_limit[TEMP_RANGE_MAX][VOLT_RANGE_MAX] = {
 };
 
 static const struct battery_info info = {
-	/* Designed voltage
+	/*
+	 * Design voltage
 	 *   max    = 8.4V
 	 *   normal = 7.4V
 	 *   min    = 6.0V
@@ -63,29 +60,20 @@ static const struct battery_info info = {
 	.voltage_normal = 7400,
 	.voltage_min    = 6000,
 
-	/* Operation temperation range
-	 *   0   <= T_charge    <= 50 deg C
-	 *   -20 <= T_discharge <= 60 deg C
-	 *
-	 * The temperature values below should be deci-Kelvin
+	/*
+	 * Operational temperature range
+	 *   0 <= T_charge    <= 50 deg C
+	 * -20 <= T_discharge <= 60 deg C
 	 */
-	.temp_charge_min    =   0 * 10 + 2731,
-	.temp_charge_max    =  50 * 10 + 2731,
-	.temp_discharge_min = -20 * 10 + 2731,
-	.temp_discharge_max =  60 * 10 + 2731,
+	.temp_charge_min    = CELSIUS_TO_DECI_KELVIN(0),
+	.temp_charge_max    = CELSIUS_TO_DECI_KELVIN(50),
+	.temp_discharge_min = CELSIUS_TO_DECI_KELVIN(-20),
+	.temp_discharge_max = CELSIUS_TO_DECI_KELVIN(60),
 
-	/* Pre-charge voltage and current
-	 *   I <= 0.01C
-	 */
-	.precharge_current  = C_001,
+	/* Pre-charge current: I <= 0.01C */
+	.precharge_current  = (int)(DESIGN_CAPACITY * 0.01),
 };
 
-/* Convert Celsius degree to Deci Kelvin degree */
-static inline int celsius_to_deci_kelvin(int degree_c)
-{
-	return degree_c * 10 + 2731;
-}
-
 static inline void limit_value(int *val, int limit)
 {
 	if (*val > limit)
@@ -97,18 +85,16 @@ const struct battery_info *battery_get_info(void)
 	return &info;
 }
 
-/* Vendor provided parameters for battery charging */
 void battery_vendor_params(struct batt_params *batt)
 {
 	int *desired_current = &batt->desired_current;
 	int temp_range, volt_range;
 
-	/* Hard limits
-	 *  - charging voltage < 8.4V
-	 *  - charging temperature range 0 ~ 45 degree Celcius
-	 *  */
+	/* Limit charging voltage */
 	if (batt->desired_voltage > info.voltage_max)
 		batt->desired_voltage = info.voltage_max;
+
+	/* Don't charge if outside of allowable temperature range */
 	if (batt->temperature >= info.temp_charge_max ||
 	    batt->temperature <= info.temp_charge_min) {
 		batt->desired_voltage = 0;
@@ -116,13 +102,13 @@ void battery_vendor_params(struct batt_params *batt)
 		return;
 	}
 
-	if (batt->temperature <= celsius_to_deci_kelvin(10))
+	if (batt->temperature <= CELSIUS_TO_DECI_KELVIN(10))
 		temp_range = TEMP_RANGE_10;
-	else if (batt->temperature <= celsius_to_deci_kelvin(23))
+	else if (batt->temperature <= CELSIUS_TO_DECI_KELVIN(23))
 		temp_range = TEMP_RANGE_23;
-	else if (batt->temperature <= celsius_to_deci_kelvin(35))
+	else if (batt->temperature <= CELSIUS_TO_DECI_KELVIN(35))
 		temp_range = TEMP_RANGE_35;
-	else if (batt->temperature <= celsius_to_deci_kelvin(45))
+	else if (batt->temperature <= CELSIUS_TO_DECI_KELVIN(45))
 		temp_range = TEMP_RANGE_45;
 	else
 		temp_range = TEMP_RANGE_50;
@@ -137,11 +123,13 @@ void battery_vendor_params(struct batt_params *batt)
 	limit_value(desired_current, current_limit[temp_range][volt_range]);
 
 #ifndef CONFIG_SLOW_PRECHARGE
-	/* Trickle charging and pre-charging current should be 0.01 C */
+	/* Always request some current for trickle charging and pre-charging */
+	/*
+	 * TODO: (crosbug.com/p/15573) Shouldn't we only do this if desired
+	 * current is non-zero?
+	 */
 	if (*desired_current < info.precharge_current)
 		*desired_current = info.precharge_current;
 #endif /* CONFIG_SLOW_PRECHARGE */
 
 }
-
-
diff --git a/include/battery_pack.h b/include/battery_pack.h
index c119c673c0..10022ddac1 100644
--- a/include/battery_pack.h
+++ b/include/battery_pack.h
@@ -9,33 +9,39 @@
 
 /* Battery parameters */
 struct batt_params {
-	int temperature;
-	int state_of_charge;
-	int voltage;
-	int current;
-	int desired_voltage;
-	int desired_current;
+	int temperature;      /* Temperature in 0.1 K */
+	int state_of_charge;  /* State of charge (percent, 0-100) */
+	int voltage;          /* Battery voltage (mV) */
+	int current;          /* Battery current (mA) */
+	int desired_voltage;  /* Charging voltage desired by battery (mV) */
+	int desired_current;  /* Charging current desired by battery (mA) */
 };
 
 /* Battery constants */
 struct battery_info {
-	/* Design voltage */
+	/* Design voltage in mV */
 	int voltage_max;
 	int voltage_normal;
 	int voltage_min;
-	/* Working temperature */
+	/* Working temperature range in 0.1 K increments */
 	int temp_charge_min;
 	int temp_charge_max;
 	int temp_discharge_min;
 	int temp_discharge_max;
-	/* Pre-charge */
+	/* Pre-charge current in mA */
 	int precharge_current;
 };
 
-/* Vendor provided battery constants */
+/**
+ * Return vendor-provided battery constants.
+ */
 const struct battery_info *battery_get_info(void);
 
-/* Vendor provided parameters for battery charging */
+/**
+ * Modify battery parameters to match vendor charging profile.
+ *
+ * @param batt		Battery parameters to modify
+ */
 void battery_vendor_params(struct batt_params *batt);
 
 #endif