charger/rt946x: fix charger Vsys short

Vsys may short if Ichg and Isys's gap is too huge, and it
will cause the system shutdown.

When the system is charging at 500mA, and if Isys > 3600mA, the
power path will be turned off and cause the system shutdown:
 - When Ichg < 400mA, then power path is roughly 1/8 of the original.
 - When Isys > 3600mA, this cause the voltage between Vbat and Vsys too
   huge (Vbat - Vsys > Vsys short portection) and turns off the power
   path.

To workaround this, we have to
1. disable Vsys short protection when Ichg is set below 900mA
2. forbids Ichg <= 400mA (this is done natually on mt6370, since mt6370's
   minimum current is 512)

BRANCH=kukui
BUG=b:144532905
TEST=Change ichg setting to test vsys short and
     ensure the system won't shutdown.

Change-Id: I6cbdd974f6f0cc94ebd82d419304a0d4e67fcaff
Signed-off-by: Yilun Lin <yllin@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1924169
Reviewed-by: Ting Shen <phoenixshen@chromium.org>

2 files changed, 60 insertions, 0 deletions

diff --git a/driver/charger/rt946x.c b/driver/charger/rt946x.c
index b864acaf3f..f389188bad 100644
--- a/driver/charger/rt946x.c
+++ b/driver/charger/rt946x.c
@@ -312,6 +312,53 @@ out:
 	mutex_unlock(&hidden_mode_lock);
 	return rv;
 }
+
+/*
+ * Vsys short protection:
+ * When the system is charging at 500mA, and if Isys > 3600mA, the
+ * power path will be turned off and cause the system shutdown.
+ * When Ichg < 400mA, then power path is roughly 1/8 of the original.
+ * When Isys > 3600mA, this cause the voltage between Vbat and Vsys too
+ * huge (Vbat - Vsys > Vsys short portection) and turns off the power
+ * path.
+ * To workaround this,
+ * 1. disable Vsys short protection when Ichg is set below 900mA
+ * 2. forbids Ichg <= 400mA (this is done natually on mt6370, since mt6370's
+ *    minimum current is 512)
+ */
+static int mt6370_ichg_workaround(int new_ichg)
+{
+	int rv = EC_SUCCESS;
+	int curr_ichg;
+
+	/*
+	 * TODO(b:144532905): The workaround should be applied to rt9466 as
+	 * well. But this needs rt9466's hidden register datasheet. Enable
+	 * this if we need it in the future.
+	 */
+	if (!IS_ENABLED(CONFIG_CHARGER_MT6370))
+		return EC_SUCCESS;
+
+	rv = charger_get_current(&curr_ichg);
+	if (rv)
+		return rv;
+
+	mt6370_enable_hidden_mode(1);
+
+	/* disable Vsys protect if if the new ichg is below 900mA */
+	if (curr_ichg >= 900 && new_ichg < 900)
+		rv = rt946x_update_bits(RT946X_REG_CHGHIDDENCTRL7,
+					RT946X_MASK_HIDDENCTRL7_VSYS_PROTECT,
+					0);
+	/* enable Vsys protect if the new ichg is above 900mA */
+	else if (new_ichg >= 900 && curr_ichg < 900)
+		rv = rt946x_update_bits(RT946X_REG_CHGHIDDENCTRL7,
+					RT946X_MASK_HIDDENCTRL7_VSYS_PROTECT,
+					RT946X_ENABLE_VSYS_PROTECT);
+
+	mt6370_enable_hidden_mode(0);
+	return rv;
+}
 #endif /* CONFIG_CHARGER_MT6370 */
 
 static int rt946x_chip_rev(int *chip_rev)
@@ -782,6 +829,11 @@ int charger_set_current(int current)
 	if (IS_ENABLED(CONFIG_CHARGER_MT6370))
 		current = MAX(500, current);
 
+#ifdef CONFIG_CHARGER_MT6370
+	rv = mt6370_ichg_workaround(current);
+	if (rv)
+		return rv;
+#endif
 
 	reg_icc = rt946x_closest_reg(info->current_min, info->current_max,
 				     info->current_step, current);
diff --git a/driver/charger/rt946x.h b/driver/charger/rt946x.h
index 9797e95255..6b0228bb3b 100644
--- a/driver/charger/rt946x.h
+++ b/driver/charger/rt946x.h
@@ -124,6 +124,7 @@
 #define MT6370_REG_QCSTATUS2		0x29
 #define RT946X_REG_CHGCTRL17		0X2B
 #define RT946X_REG_CHGCTRL18		0X2C
+#define RT946X_REG_CHGHIDDENCTRL7	0x36
 #define MT6370_REG_CHGHIDDENCTRL15	0x3E
 #define RT946X_REG_CHGSTAT		0X4A
 #define RT946X_REG_CHGNTC		0X4B
@@ -444,6 +445,13 @@
 				MT6370_MASK_APP_DPDM_IN | \
 				MT6370_MASK_APP_REF)
 
+/* ========= CHGHIDDENCTRL7 0x36 (mt6370) ======== */
+#define RT946X_ENABLE_VSYS_PROTECT		0x40
+
+#define RT946X_SHIFT_HIDDENCTRL7_VSYS_PROTECT	5
+#define RT946X_MASK_HIDDENCTRL7_VSYS_PROTECT \
+	(0x3 << RT946X_SHIFT_HIDDENCTRL7_VSYS_PROTECT)
+
 /* ========== CHGCTRL18 0x1A ============ */
 #define RT946X_SHIFT_IRCMP_RES		3
 #define RT946X_SHIFT_IRCMP_VCLAMP	0