BD9995X: Disable input current limiting for VBAT < VSYSREG_SET

The initial value for input current limit is set to
CONFIG_CHARGER_INPUT_CURRENT which is typically 512 mA. In deeply
discharged battery cases (Vbat < 5.8V), the 512 mA input current limit
can cause VSYS to collapse which in turn causes the EC to
reset. Depending on how discharged the battery is, the EC may remain
off until the external charger is disconnected and reconnected again,
or it may undergo a number of reset cycles, each time charging the
battery just a little, until Vbat becomes > ~5.8V and the charger is
able to stabilize. When the charger type is determined, either from
BCD detection, or Type C/USB PD, the input current limit is set to the
appropriate level.

In order to avoid the issue described above, this CL sets a bit in the
VIN_CTRL_SET register which will disable the input current limit in cases
Where the VBAT is less than the VSYSREG_SET value.

BUG=b:35648317
BRANCH=none
TEST=Manually tested on Electro.
     a. With Zinger attached DUT boots without the battery after
        plugging in AC
     b. DUT boots from cut-off battery
     c. With Zinger attached DUT boots from cold-reset without the
        battery
     d. With no battery & DCP charger, anti-collapse occurs,
        input current is limited to 512mA & the DUT is
        power-up inhibited.

Tested also on Eve with signal wires attached to both PPVAR_VSYS,
PP3300_DSW, and Vbat. Verified that on certain boards (some board to
board variation) that PPVAT_VSYS would collapse when the input current
limit was set to CONFIG_CHARGER_INPUT_CURRENT. Then after adding this
CL, verifed on the scope that the collapse of PPVAR_VSYS no longer
occurred.

Change-Id: Ief9960550f988e69ab4637db85450e91c70d3b51
Signed-off-by: Vijay Hiremath <vijay.p.hiremath@intel.com>
Reviewed-on: https://chromium-review.googlesource.com/456049
Commit-Ready: Vijay Hiremath <vijay.p.hiremath@intel.corp-partner.google.com>
Tested-by: Scott Collyer <scollyer@chromium.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Vijay Hiremath <vijay.p.hiremath@intel.corp-partner.google.com>

2 files changed, 29 insertions, 1 deletions

diff --git a/driver/charger/bd9995x.c b/driver/charger/bd9995x.c
index 538a9ea714..7ee385680d 100644
--- a/driver/charger/bd9995x.c
+++ b/driver/charger/bd9995x.c
@@ -30,6 +30,7 @@
  * completes 312ms after VBUS/VCC attach.
  */
 #define BC12_DETECT_US (312*MSEC)
+#define BD9995X_VSYS_PRECHARGE_OFFSET_MV 200
 
 /* Console output macros */
 #define CPRINTS(format, args...) cprints(CC_CHARGER, format, ## args)
@@ -203,7 +204,8 @@ static int bd9995x_charger_enable(int enable)
 		 * Set VSYSREG_SET > VBAT so that the charger is in Pre-Charge
 		 * state when not charging or discharging.
 		 */
-		rv = bd9995x_set_vsysreg(bi->voltage_max + 200);
+		rv = bd9995x_set_vsysreg(bi->voltage_max +
+					 BD9995X_VSYS_PRECHARGE_OFFSET_MV);
 
 		/*
 		 * Allow charger in pre-charge state for 50ms before disabling
@@ -819,6 +821,15 @@ static void bd9995x_init(void)
 	ch_raw_write16(BD9995X_CMD_CHGOP_SET1, reg,
 		       BD9995X_EXTENDED_COMMAND);
 
+	/*
+	 * OTP setting for this register is 6.08V. Set VSYS to above battery max
+	 * (as is done when charger is disabled) to ensure VSYSREG_SET > VBAT so
+	 * that the charger is in Pre-Charge state and that the input current
+	 * disable setting below will be active.
+	 */
+	bd9995x_set_vsysreg(battery_get_info()->voltage_max +
+			    BD9995X_VSYS_PRECHARGE_OFFSET_MV);
+
 	/* Enable BC1.2 USB charging and DC/DC converter @ 1200KHz */
 	if (ch_raw_read16(BD9995X_CMD_CHGOP_SET2, &reg,
 			  BD9995X_EXTENDED_COMMAND))
@@ -841,6 +852,21 @@ static void bd9995x_init(void)
 		return;
 	reg &= ~BD9995X_CMD_VM_CTRL_SET_EXTIADPEN;
 	ch_raw_write16(BD9995X_CMD_VM_CTRL_SET, reg, BD9995X_EXTENDED_COMMAND);
+	/*
+	 * Disable the input current limit when VBAT is < VSYSREG_SET. This
+	 * needs to be done before calling
+	 * bd9995x_battery_charging_profile_settings() as in that function the
+	 * input current limit is set to CONFIG_CHARGER_INPUT_CURRENT which is
+	 * 512 mA. In deeply discharged battery cases, setting the input current
+	 * limit this low can cause VSYS to collapse, which in turn can cause
+	 * the EC's brownout detector to reset the EC.
+	 */
+	if (ch_raw_read16(BD9995X_CMD_VIN_CTRL_SET, &reg,
+			  BD9995X_EXTENDED_COMMAND))
+		return;
+	reg |= BD9995X_CMD_VIN_CTRL_SET_VSYS_PRIORITY;
+	ch_raw_write16(BD9995X_CMD_VIN_CTRL_SET, reg,
+		       BD9995X_EXTENDED_COMMAND);
 
 	/* Define battery charging profile */
 	bd9995x_battery_charging_profile_settings();
diff --git a/driver/charger/bd9995x.h b/driver/charger/bd9995x.h
index 2799973584..892e76cf10 100644
--- a/driver/charger/bd9995x.h
+++ b/driver/charger/bd9995x.h
@@ -94,6 +94,8 @@ enum bd9995x_charge_port {
 #define BD9995X_CMD_EXT_ICC_LIM_SET	0x08
 #define BD9995X_CMD_IOTG_LIM_SET	0x09
 #define BD9995X_CMD_VIN_CTRL_SET	0x0A
+#define BD9995X_CMD_VIN_CTRL_SET_VSYS_PRIORITY	(1 << 4)
+
 #define BD9995X_CMD_VIN_CTRL_SET_PP_BOTH_THRU  (1 << 11)
 #define BD9995X_CMD_VIN_CTRL_SET_VBUS_PRIORITY (1 << 7)
 #define BD9995X_CMD_VIN_CTRL_SET_VBUS_EN       (1 << 6)