scarlet: Cut off battery in a custom battery condition

We want to shut down AP when the battery charge drops below
BATTERY_LEVEL_SHUTDOWN. Then we want to cut off the battery
to protect the battery from over-discharging.

But we don't want to cut off the battery right after the battery charge
drops below BATTERY_LEVEL_SHUTDOWN so that we can retain the RTC timestamp
for functionality reasons.

So let's add a custom check before we move on to cut off the battery in
shutdown_on_critical_battery().

BUG=b:68723854
BRANCH=scarlet
TEST=keep the battery discharging, see AP shut down when
battery charge hits 2% and later EC cut off battery when
battery voltage hits 3.2V

Change-Id: I9950cf32558c11a2f55ee6ca64c157146d449110
Signed-off-by: Philip Chen <philipchen@google.com>
Reviewed-on: https://chromium-review.googlesource.com/1121593
Reviewed-by: Alexandru M Stan <amstan@chromium.org>
Commit-Queue: Philip Chen <philipchen@chromium.org>
Tested-by: Philip Chen <philipchen@chromium.org>
Trybot-Ready: Philip Chen <philipchen@chromium.org>

3 files changed, 27 insertions, 12 deletions

diff --git a/board/scarlet/board.h b/board/scarlet/board.h
index a6120be824..b164dfa752 100644
--- a/board/scarlet/board.h
+++ b/board/scarlet/board.h
@@ -120,6 +120,11 @@
 #define CONFIG_USBC_VCONN_SWAP
 #define CONFIG_USB_PD_COMM_LOCKED
 
+#define CONFIG_BATTERY_CRITICAL_SHUTDOWN_CUT_OFF
+#undef  CONFIG_BATTERY_CRITICAL_CUT_OFF_CUSTOM_CONDITION
+#define CONFIG_BATTERY_CRITICAL_CUT_OFF_CUSTOM_CONDITION \
+	((curr.batt.flags & BATT_FLAG_BAD_VOLTAGE) || \
+	 (curr.batt.voltage <= BAT_LOW_VOLTAGE_THRESH))
 #define CONFIG_BATTERY_CUT_OFF
 #define CONFIG_BATTERY_PRESENT_CUSTOM
 #define CONFIG_BATTERY_RETRY_NACK
diff --git a/common/charge_state_v2.c b/common/charge_state_v2.c
index a02b35189b..b274712deb 100644
--- a/common/charge_state_v2.c
+++ b/common/charge_state_v2.c
@@ -1141,10 +1141,13 @@ static inline int battery_too_low(void)
 }
 
 
-/*
- * Send host event to the AP if the battery is temperature or charge level
- * is critical. Force-shutdown if the problem isn't corrected after timeout.
- */
+ /*
+  * If the battery is at extremely low charge (and discharging) or extremely
+  * high temperature, the EC will notify the AP and start a timer. If the
+  * critical condition is not corrected before the timeout expires, the EC
+  * will shut down the AP (if the AP is not already off) and then optionally
+  * hibernate or cut off battery.
+  */
 static int shutdown_on_critical_battery(void)
 {
 	int batt_temp_c;
@@ -1184,9 +1187,11 @@ static int shutdown_on_critical_battery(void)
 		if (chipset_in_state(CHIPSET_STATE_ANY_OFF)) {
 			/* Timeout waiting for charger to provide more power */
 #if defined(CONFIG_BATTERY_CRITICAL_SHUTDOWN_CUT_OFF)
-			CPRINTS(
-			  "charge force battery cut-off due to critical level");
-			board_cut_off_battery();
+			if (CONFIG_BATTERY_CRITICAL_CUT_OFF_CUSTOM_CONDITION) {
+				CPRINTS("charge force battery cut-off due to "
+					"critical level");
+				board_cut_off_battery();
+			}
 #elif defined(CONFIG_HIBERNATE)
 			CPRINTS(
 			  "charge force EC hibernate due to critical battery");
diff --git a/include/config.h b/include/config.h
index 5e764386d4..7ccb54b364 100644
--- a/include/config.h
+++ b/include/config.h
@@ -301,11 +301,10 @@
  * Critical battery shutdown timeout (seconds)
  *
  * If the battery is at extremely low charge (and discharging) or extremely
- * high temperature, the EC will shut itself down. This defines the timeout
- * period in seconds between the critical condition being detected and the
- * EC shutting itself down. Note that if the critical condition is corrected
- * before the timeout expiration, the EC will not shut itself down.
- *
+ * high temperature, the EC will notify the AP and start a timer with the
+ * timeout defined here. If the critical condition is not corrected before
+ * the timeout expires, the EC will shut down the AP (if the AP is not already
+ * off) and then optionally hibernate or cut off battery.
  */
 #define CONFIG_BATTERY_CRITICAL_SHUTDOWN_TIMEOUT 30
 
@@ -313,6 +312,12 @@
 #undef CONFIG_BATTERY_CRITICAL_SHUTDOWN_CUT_OFF
 
 /*
+ * The extra condition we want to meet before cutting off battery
+ * when we found the battery is in a critical condition.
+ */
+#define CONFIG_BATTERY_CRITICAL_CUT_OFF_CUSTOM_CONDITION 1
+
+/*
  * Support battery cut-off as host command and console command.
  *
  * Once defined, you have to implement a board_cut_off_battery() function