--- src-b10b3/drivers/power/supply/pm8916_lbc.c	2026-10-03 21:11:03.584000000 +0600
+++ src-b10b5/drivers/power/supply/pm8916_lbc.c	2026-10-04 20:07:45.456000000 +0600
@@ -298,7 +298,7 @@
 
 
 /*
- * Aurora B10B-3 v3 charger supervisor: CHARGE -> HOLD -> (battery) -> CHARGE.
+ * Aurora B10B-3 v4 charger supervisor: CHARGE -> HOLD -> (battery) -> CHARGE (v4 = v3 + FAULT safe clamp, B10B-5).
  * Facts it relies on (B10A/B10B-2/B10B-3 tests): CHG_STATUS 00 + USB path 01 is a latch, not an end-of-charge;
  * no hardware EOC was seen with BOOT_DONE set; CHG_EN = 0 does not stop the charger; verified levers are VDD_MAX,
  * IBAT_MAX and the CHG_CTRL 0x21 -> 0xa0 edge (releases the latch). All decisions use the calibrated VADC VBAT.
@@ -306,7 +306,10 @@
  *   CHARGING: entered on USB insert/probe: BOOT_DONE, VDD_MAX = charge level, IBAT_MAX, restart edge.
  *             -> HOLD after the CV loop with VBAT >= full-min lasted cv-hold-minutes; 00/01 latch -> restart, stay.
  *   HOLD:     only VDD_MAX = hold level; 00/01 latch -> restart edge, VDD_MAX stays at the hold level.
- *   FAULT:    logical only (VBAT > 4.25 V or CHG_FAILED): no restarts. There is no verified software stop.
+ *   FAULT:    entered on VBAT > 4.25 V or CHG_FAILED; on entry only VDD_MAX = 0x00 (FAULT safe clamp to 4.00 V, B10B-4) +
+ *             readback; no further charger writes, no restarts; left only by USB removal (-> NO_USB) or reboot.
+ *             The clamp is NOT a guaranteed charge disconnect: with VBAT > 4.00 V charging stops and the board runs
+ *             from the battery; with VBAT < 4.00 V the charger may still charge up to 4.00 V.
  */
 static void lbc_supv_log(struct pm8916_lbc_charger *chg, int to, const char *why)
 {
@@ -318,7 +321,7 @@
 	chg->log[i].vbat = chg->vbat_uv;
 	chg->log[i].why = why;
 	if (to == LBC_ST_FAULT)
-		dev_crit(chg->dev, "supervisor %s -> FAULT (%s), vbat %d uV: restarts blocked, NO software stop available\n",
+		dev_crit(chg->dev, "supervisor %s -> FAULT (%s), vbat %d uV: restarts blocked, FAULT safe clamp to 4.00 V\n",
 			 lbc_state_name[chg->state], why, chg->vbat_uv);
 	else
 		dev_info(chg->dev, "supervisor %s -> %s (%s), vbat %d uV\n", lbc_state_name[chg->state],
@@ -394,18 +397,36 @@
 	return true;
 }
 
+/*
+ * FAULT safe clamp to 4.00 V (B10B-4): the only charger write on FAULT entry is VDD_MAX = 0x00 (lowest LBC step).
+ * Not a guaranteed charge disconnect - below 4.00 V the charger may still charge up to 4.00 V.
+ */
+static void lbc_fault_clamp(struct pm8916_lbc_charger *chg, const char *why)
+{
+	unsigned int old = 0xff, rb = 0xff;
+	int ret;
+
+	ret = regmap_read(chg->regmap, chg->reg[LBC_CHGR] + PM8916_LBC_CHGR_VDD_MAX, &old);
+	ret = ret ?: regmap_write(chg->regmap, chg->reg[LBC_CHGR] + PM8916_LBC_CHGR_VDD_MAX, 0x00);
+	ret = ret ?: regmap_read(chg->regmap, chg->reg[LBC_CHGR] + PM8916_LBC_CHGR_VDD_MAX, &rb);
+	dev_crit(chg->dev, "FAULT safe clamp to 4.00 V: cause %s, vbat %d uV, VDD_MAX old 0x%02x -> readback 0x%02x (ret %d)\n",
+		 why, chg->vbat_uv, old, rb, ret);
+}
+
+static bool lbc_enter_fault(struct pm8916_lbc_charger *chg, int reason, const char *why)
+{
+	chg->fault_reason = reason;
+	lbc_fault_clamp(chg, why);
+	lbc_supv_log(chg, LBC_ST_FAULT, why);
+	return true;
+}
+
 static bool lbc_check_fault(struct pm8916_lbc_charger *chg, unsigned int failed)
 {
-	if (failed & PM8916_LBC_CHGR_CHG_FAILED_BIT) {
-		chg->fault_reason = LBC_FAULT_TIMER;
-		lbc_supv_log(chg, LBC_ST_FAULT, "CHG_FAILED (safety timer)");
-		return true;
-	}
-	if (chg->vbat_uv > PM8916_LBC_SUPV_OVP_UV) {
-		chg->fault_reason = LBC_FAULT_OVP;
-		lbc_supv_log(chg, LBC_ST_FAULT, "vbat > 4.25 V");
-		return true;
-	}
+	if (failed & PM8916_LBC_CHGR_CHG_FAILED_BIT)
+		return lbc_enter_fault(chg, LBC_FAULT_TIMER, "CHG_FAILED (safety timer)");
+	if (chg->vbat_uv > PM8916_LBC_SUPV_OVP_UV)
+		return lbc_enter_fault(chg, LBC_FAULT_OVP, "vbat > 4.25 V");
 	return false;
 }