fruitpie: disable battery charging chip ILIM pin

Typically bq24xxx charging chip limits input current to minimum of
register value and ILIM pin. For fruitpie, the current limit will
be decided solely in software, and the hardware pin will be ignored.

BUG=chrome-os-partner:28611,chrome-os-partner:28311
BRANCH=none
TEST=Tested on fruitpie. Verified that current limit can be set
above the ILIM pin value of 500mA.

Change-Id: Ia687446f95f9d18fde9d2b4ebb0e1c093aebf885
Signed-off-by: Alec Berg <alecaberg@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/198940
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

board/fruitpie/board.h

@@ -42,6 +42,7 @@
 #define CONFIG_CHARGER_SENSE_RESISTOR     5 /* milliOhms */
 #define CONFIG_CHARGER_SENSE_RESISTOR_AC 10 /* milliOhms */
 #define CONFIG_CHARGER_INPUT_CURRENT    512 /* mA */
+#define CONFIG_CHARGER_ILIM_PIN_DISABLED    /* external ILIM pin disabled */
 
 /*
  * Allow dangerous commands all the time, since we don't have a write protect

driver/charger/bq24773.c

@@ -170,9 +170,28 @@ int charger_set_voltage(int voltage)
 int charger_post_init(void)
 {
 	int rv;
+#ifdef CONFIG_CHARGER_ILIM_PIN_DISABLED
+	int option2;
+#endif
 
 	/* Set charger input current limit */
 	rv = charger_set_input_current(CONFIG_CHARGER_INPUT_CURRENT);
+
+#ifdef CONFIG_CHARGER_ILIM_PIN_DISABLED
+	if (rv)
+		return rv;
+
+	/* Disable the external ILIM pin. */
+	rv = i2c_read16(I2C_PORT_CHARGER, BQ24773_ADDR,
+			   BQ24773_CHARGE_OPTION2, &option2);
+	if (rv)
+		return rv;
+
+	option2 &= ~OPTION2_EN_EXTILIM;
+	rv = i2c_write16(I2C_PORT_CHARGER, BQ24773_ADDR,
+			   BQ24773_CHARGE_OPTION2, option2);
+#endif
+
 	return rv;
 }
 

driver/charger/bq24773.h

@@ -28,4 +28,6 @@
 #define OPTION0_CHARGE_INHIBIT          (1 << 0)
 #define OPTION0_LEARN_ENABLE            (1 << 5)
 
+#define OPTION2_EN_EXTILIM              (1 << 7)
+
 #endif /* __CROS_EC_CHARGER_BQ24773_H */

include/config.h

@@ -204,6 +204,13 @@
  */
 #undef CONFIG_CHARGER_DISCHARGE_ON_AC
 
+/*
+ * Board specific flag used to disable external ILIM pin used to determine input
+ * current limit. When defined, the input current limit is decided only by
+ * the software register value.
+ */
+#undef CONFIG_CHARGER_ILIM_PIN_DISABLED
+
 /*
  * Maximum amount of input current the charger can receive, in mA.
  *