extcon: intel-cht-wc: Disable external 5v boost converter on probe

Disable the 5v boost converter on probe in case it was left on by
the BIOS, this fixes 2 problems:

1) This gets seen by the external battery charger as a valid Vbus
   supply and it then tries to feed Vsys from this creating a
   feedback loop which causes aprox. 300 mA extra battery drain
   (and unless we drive the external-charger-disable pin high it
   also tries to charge the battery causing even more feedback).
2) This gets seen by the pwrsrc block as a SDP USB Vbus supply

Since the external battery charger has its own 5v boost converter
which does not have these issues, we simply turn the separate
external 5v boost converter off and leave it off entirely.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>

drivers/extcon/extcon-intel-cht-wc.c

@@ -64,6 +64,9 @@
 #define CHT_WC_PWRSRC_ID_GND		BIT(3)
 #define CHT_WC_PWRSRC_ID_FLOAT		BIT(4)
 
+#define CHT_WC_VBUS_GPIO_CTLO		0x6e2d
+#define CHT_WC_VBUS_GPIO_CTLO_OUTPUT	BIT(0)
+
 enum cht_wc_usb_id {
 	USB_ID_OTG,
 	USB_ID_GND,
@@ -170,6 +173,23 @@ static void cht_wc_extcon_set_phymux(struct cht_wc_extcon_data *ext, u8 state)
 		dev_err(ext->dev, "Error writing phyctrl: %d\n", ret);
 }
 
+static void cht_wc_extcon_set_5v_boost(struct cht_wc_extcon_data *ext,
+				       bool enable)
+{
+	int ret, val;
+
+	val = enable ? CHT_WC_VBUS_GPIO_CTLO_OUTPUT : 0;
+
+	/*
+	 * The 5V boost converter is enabled through a gpio on the PMIC, since
+	 * there currently is no gpio driver we access the gpio reg directly.
+	 */
+	ret = regmap_update_bits(ext->regmap, CHT_WC_VBUS_GPIO_CTLO,
+				 CHT_WC_VBUS_GPIO_CTLO_OUTPUT, val);
+	if (ret)
+		dev_err(ext->dev, "Error writing Vbus GPIO CTLO: %d\n", ret);
+}
+
 /* Small helper to sync EXTCON_CHG_USB_SDP and EXTCON_USB state */
 static void cht_wc_extcon_set_state(struct cht_wc_extcon_data *ext,
 				    unsigned int cable, bool state)
@@ -280,6 +300,21 @@ static int cht_wc_extcon_probe(struct platform_device *pdev)
 	if (IS_ERR(ext->edev))
 		return PTR_ERR(ext->edev);
 
+	/*
+	 * When a host-cable is detected the BIOS enables an external 5v boost
+	 * converter to power connected devices there are 2 problems with this:
+	 * 1) This gets seen by the external battery charger as a valid Vbus
+	 *    supply and it then tries to feed Vsys from this creating a
+	 *    feedback loop which causes aprox. 300 mA extra battery drain
+	 *    (and unless we drive the external-charger-disable pin high it
+	 *    also tries to charge the battery causing even more feedback).
+	 * 2) This gets seen by the pwrsrc block as a SDP USB Vbus supply
+	 * Since the external battery charger has its own 5v boost converter
+	 * which does not have these issues, we simply turn the separate
+	 * external 5v boost converter off and leave it off entirely.
+	 */
+	cht_wc_extcon_set_5v_boost(ext, false);
+
 	/* Enable sw control */
 	ret = cht_wc_extcon_sw_control(ext, true);
 	if (ret)